Other articles by Sandeep Khurana on PubMed

• Lithocholylcholine, a Bile Acid/acetylcholine Hybrid, is a Muscarinic Receptor Antagonist The Journal of Pharmacology and Experimental Therapeutics. Oct, 2002  |   Pubmed ID: 12235229 Previous work from our laboratory indicates that bile acids, specifically lithocholic acid conjugates, interact with muscarinic receptors on gastric chief cells. Structural similarities between acetylcholine and lithocholyltaurine suggest a potential molecular basis for their interaction with the same receptor. We synthesized a hybrid molecule consisting of the steroid nucleus of lithocholyltaurine and the choline moiety of acetylcholine. The new molecule, lithocholylcholine, is hydrolyzed by acetyl-cholinesterase. Lithocholylcholine inhibited binding of a cholinergic radioligand to Chinese hamster ovary cells expressing each of the five muscarinic receptor subtypes. The binding affinities (K(i); micromolar) of lithocholylcholine for these receptors were: M3 (1.0) > M1 (2.7) > M2 (4.1) = M4 (4.9) > M5 (6.2). Lithocholylcholine inhibited intracellular signaling pathways mediated by interaction with M1, M2, and M3 muscarinic receptors. Regarding M3 receptors, lithocholylcholine was 10-fold more potent than lithocholyltaurine in terms of binding affinity and inhibition of acetylcholine-induced increases in inositol phosphate formation and mitogen-activated protein kinase phosphorylation. In a functional assay, lithocholylcholine inhibited acetylcholine-induced relaxation of rat aortic rings. These observations indicate that lithocholylcholine is a muscarinic receptor antagonist and provide further evidence that bile acids may have gastrointestinal signaling functions that extend beyond their effects on sterol metabolism, lipid absorption, and cholesterol elimination. Hybrid molecules created from bile acids and acetylcholine may be used to develop selective muscarinic receptor ligands.
• Patch Testing in Discoid Eczema The Journal of Dermatology. Dec, 2002  |   Pubmed ID: 12532040 Fifty patients of both sexes with clinically suspected discoid eczema were patch tested with the Indian Standard Patch Test Battery approved by the Contact and Occupational Dermatosis Forum of India (CODFI). Most of these patients were young adults between 20 and 39 years old, with a mean age of 36 years. The mean duration of symptoms was 21/2 years. The occupational profiles of the patients included farmers (24%), housewives (18%), students (14%), housewives engaged in farming (12%), shopkeepers (10%), and laborers (8%). The miscellaneous group, including technicians, drivers, cable operators, office workers, and computer operators, accounted for the remaining 14%. The common clinical patterns of presentation of discoid eczema included hands and feet (44%), hands and forearms' (30%), legs and feet (12%) and trunk and limbs (12%). Patch test analysis of these patients revealed that, out of the 50 subjects tested, 28 (56%) reacted to one or more allergens. Potassium dichromate was the most common allergen (20%), followed by nickel (16%), cobalt chloride, and fragrance (12% each) in decreasing order of frequency. Hence, it may be concluded that patch testing should be considered for all patients with severe or persistent discoid eczema because allergic contact dermatitis may be relatively common in such patients and the avoidance of offending allergens may be of substantial benefit to the patients.
• Vasodilatory Effects of Cholinergic Agonists Are Greatly Diminished in Aorta from M3R-/- Mice European Journal of Pharmacology. Jun, 2004  |   Pubmed ID: 15189773 Acetylcholine interacts with endothelial muscarinic receptors to enhance nitric oxide (NO) release and thereby cause vasodilation. The present study was designed to determine if this effect of acetylcholine is mediated by muscarinic M3 receptors. Thoracic aortae were isolated from wild-type (WT) and M3 receptor knock out (M3R-/-) male mice, and endothelium-intact (I) and -denuded (D) aortic rings were bathed in physiological buffer. Preparations were utilized to examine the contractile response to phenylephrine (1 x 10(-8) - 3 x 10(-4) M added cumulatively) and the vasodilatory actions of acetylcholine (10(-8) - 10(-4) M), carbachol (10(-9) - 10(-4) M), ATP (3 x 10(-5) M) and the NO donor SIN-1 (10(-4) M), each added in the presence of phenylephrine. Endothelium-dependent vasodilatory effects of acetylcholine and carbachol were obvious in aortae isolated from WT mice (56.3 +/- 9.8% and 49.1 +/- 4.1% reductions, respectively, in phenylephrine-induced contraction; p < 0.05), while acetylcholine and carbachol-associated relaxations observed in endothelium-intact M3R-/- preparations (17.9 +/- 2.6% and 13.5 +/- 4.2% reductions, respectively) did not differ significantly from time-control values. ATP-induced, endothelium-dependent vasodilation was similar in preparations from M3R-/- and WT mice, and SIN-1 elicited similar dilatory effects in intact and denuded WT and M3R-/- segments. Phenylephrine concentration-response curves were shifted leftwards by removal of the endothelium in both groups (EC50 values: WT-I/D--25.59 +/- 6.86/3.13 +/- 1.01 x 10(-7) M; M3R-/-I/D--13.92 +/- 4.21/1.52 +/- 0.46 x 10(-7) M; both p < 0.05); however, the phenylephrine response did not differ significantly when compared between the WT and M3R-/- groups. These results indicate that the attenuated vasodilatory effect of acetylcholine in endothelium-intact aortae from M3R-/- mice is due to the absence of muscarinic M3 receptors, and thus suggest that in mouse aorta, muscarinic M3 receptors play a major role in the endothelium-dependent acetylcholine-induced vasodilation.
• Deoxycholyltaurine-induced Vasodilation of Rodent Aorta is Nitric Oxide- and Muscarinic M(3) Receptor-dependent European Journal of Pharmacology. Jul, 2005  |   Pubmed ID: 15964566 Emerging evidence indicates that some secondary bile acids interact functionally with muscarinic cholinergic receptors. Using thoracic aortic rings prepared from rats and mice, we examined the mechanism of deoxycholyltaurine-induced vasorelaxation. Increasing concentrations of both acetylcholine (1 nM to 0.1 mM) and deoxycholyltaurine (0.1 microM to 1 mM) stimulated relaxation of phenylephrine-constricted rings prepared from rat thoracic aortae. These effects were reduced by endothelial denudation and by treatment with an inhibitor of nitric oxide formation and with a synthetic acetylcholine:bile acid hybrid that acts as a muscarinic receptor antagonist. Likewise, both acetylcholine (1 nM to 0.1 mM) and deoxycholyltaurine (0.1 microM to 0.1 mM) stimulated relaxation of phenylephrine-constricted rings prepared from mouse thoracic aortae. These effects were reduced by endothelial denudation, addition of an inhibitor of nitric oxide formation, and by muscarinic M(3) receptor knockout. We conclude that the systemic vasodilatory actions of deoxycholyltaurine are mediated in part by a nitric oxide-, muscarinic M(3) receptor-dependent mechanism. In advanced liver disease, interaction of serum bile acids with endothelial muscarinic receptors may explain nitric oxide overproduction in the systemic circulation and resulting peripheral arterial vasodilation.
• Rifampin is Safe for Treatment of Pruritus Due to Chronic Cholestasis: a Meta-analysis of Prospective Randomized-controlled Trials Liver International : Official Journal of the International Association for the Study of the Liver. Oct, 2006  |   Pubmed ID: 16953834 To determine the safety and efficacy of rifampin for treatment of pruritus associated with cholestasis due to chronic liver disease.
• Genetic Ablation of M3 Muscarinic Receptors Attenuates Murine Colon Epithelial Cell Proliferation and Neoplasia Cancer Research. May, 2008  |   Pubmed ID: 18483237 Colon epithelial cells express and most colon cancers overexpress M(3) muscarinic receptors (M(3)R). In human colon cancer cells, post-M(3)R signaling stimulates proliferation. To explore the importance of M(3)R expression in vivo, we used the azoxymethane-induced colon neoplasia model. Mice treated with weekly i.p. injection of saline [10 wild-type (WT) mice] or azoxymethane (22 WT and 16 M(3)R(-/-) mice) for 6 weeks were euthanized at 20 weeks. At week 20, azoxymethane-treated WT mice weighed approximately 16% more than M(3)R(-/-) mice (33.4 grams +/- 1.0 grams versus 27.9 grams +/- 0.5 grams; mean +/- SE, P < 0.001). In azoxymethane-treated M(3)R(-/-) mice, cell proliferation (BrdUrd staining) was reduced 43% compared with azoxymethane-treated WT mice (P < 0.05). Whereas control mice (both WT and M(3)R(-/-)) had no colon tumors, azoxymethane-treated WT mice had 5.3 +/- 0.5 tumors per animal. Strikingly, azoxymethane-treated M(3)R(-/-) mice had only 3.2 +/- 0.3 tumors per mouse (P < 0.05), a 40% reduction. Tumor volume in azoxymethane-treated M(3)R(-/-) mice was reduced 60% compared with azoxymethane-treated WT mice (8.1 mm(3) +/- 1.5 mm(3) versus 20.3 mm(3) +/- 4.1 mm(3); P < 0.05). Compared with WT, fewer M(3)R(-/-) mice had adenomas (6% versus 36%; P = 0.05), and M(3)R(-/-) mice had fewer adenocarcinomas per mouse (0.6 +/- 0.1 versus 1.7 +/- 0.4; P < 0.05). Eleven of 22 WT but no M(3)R(-/-) mice had multiple adenocarcinomas (P < 0.001). Compared with WT, azoxymethane-treated M(3)R-deficient mice have attenuated epithelial cell proliferation, tumor number, and size. M(3)R and post-M(3)R signaling are novel therapeutic targets for colon cancer.
• Muscarinic Receptors and Ligands in Cancer American Journal of Physiology. Cell Physiology. Feb, 2009  |   Pubmed ID: 19036940 Emerging evidence indicates that muscarinic receptors and ligands play key roles in regulating cellular proliferation and cancer progression. Both neuronal and nonneuronal acetylcholine production results in neurocrine, paracrine, and autocrine promotion of cell proliferation, apoptosis, migration, and other features critical for cancer cell survival and spread. The present review comprises a focused critical analysis of evidence supporting the role of muscarinic receptors and ligands in cancer. Criteria are proposed to validate the biological importance of muscarinic receptor expression, activation, and postreceptor signaling. Likewise, criteria are proposed to validate the role of nonneuronal acetylcholine production in cancer. Dissecting cellular mechanisms necessary for muscarinic receptor activation as well as those needed for acetylcholine production and release will identify multiple novel targets for cancer therapy.
• Image of the Month. Acute Lymphoblastic Leukemia Presenting As Painless Jaundice Clinical Gastroenterology and Hepatology : the Official Clinical Practice Journal of the American Gastroenterological Association. Feb, 2010  |   Pubmed ID: 19607938
• Scopolamine Treatment and Muscarinic Receptor Subtype-3 Gene Ablation Augment Azoxymethane-induced Murine Liver Injury The Journal of Pharmacology and Experimental Therapeutics. Jun, 2010  |   Pubmed ID: 20197374 Previous work suggests that vagus nerve disruption reduces hepatocyte and oval cell expansion after liver injury. The role of postneuronal receptor activation in response to liver injury has not been ascertained. We investigated the actions of scopolamine, a nonselective muscarinic receptor antagonist, and specific genetic ablation of a key cholinergic receptor, muscarinic subtype-3 (Chrm3), on azoxymethane (AOM)-induced liver injury in mice. Animal weights and survival were measured as was liver injury using both gross and microscopic examination. To assess hepatocyte proliferation and apoptosis, ductular hyperplasia, and oval cell expansion, we used morphometric analysis of 5-bromo-2'-deoxyuridine-, activated caspase-3-, hematoxylin and eosin-, cytokeratin-19-, and epithelial cell adhesion molecule-stained liver sections. Sirius red staining was used as a measure of collagen deposition and its association with oval cell reaction. In AOM-treated mice, both muscarinic receptor blockade with scopolamine and Chrm3 ablation attenuated hepatocyte proliferation and augmented gross liver nodularity, apoptosis, and fibrosis. Compared with control, scopolamine-treated and Chrm3(-/-) AOM-treated mice had augmented oval cell reaction with increased ductular hyperplasia and oval cell expansion. Oval cell reaction correlated robustly with liver fibrosis. No liver injury was observed in scopolamine-treated and Chrm3(-/-) mice that were not treated with AOM. Only AOM-treated Chrm3(-/-) mice developed ascites and had reduced survival compared with AOM-treated wild-type controls. In AOM-induced liver injury, inhibiting postneuronal cholinergic muscarinic receptor activation with either scopolamine treatment or Chrm3 gene ablation results in prominent oval cell reaction. We conclude that Chrm3 plays a critical role in the liver injury response by modulating hepatocyte proliferation and apoptosis.
• Voltage-gated Divalent Currents in Descending Vasa Recta Pericytes American Journal of Physiology. Renal Physiology. Oct, 2010  |   Pubmed ID: 20630935 Multiple voltage-gated Ca(2+) channel (Ca(V)) subtypes have been reported to participate in control of the juxtamedullary glomerular arterioles of the kidney. Using the patch-clamp technique, we examined whole cell Ca(V) currents of pericytes that contract descending vasa recta (DVR). The dihydropyridine Ca(V) agonist FPL64176 (FPL) stimulated inward Ca(2+) and Ba(2+) currents that activated with threshold depolarizations to -40 mV and maximized between -20 and -10 mV. These currents were blocked by nifedipine (1 μM) and Ni(2+) (100 and 1,000 μM), exhibited slow inactivation, and conducted Ba(2+) > Ca(2+) at a ratio of 2.3:1, consistent with "long-lasting" L-type Ca(V). In FPL, with 1 mM Ca(2+) as charge carrier, Boltzmann fits yielded half-maximal activation potential (V(1/2)) and slope factors of -57.9 mV and 11.0 for inactivation and -33.3 mV and 4.4 for activation. In the absence of FPL stimulation, higher concentrations of divalent charge carriers were needed to measure basal currents. In 10 mM Ba(2+), pericyte Ca(V) currents activated with threshold depolarizations to -30 mV, were blocked by nifedipine, exhibited voltage-dependent block by diltiazem (10 μM), and conducted Ba(2+) > Ca(2+) at a ratio of ∼2:1. In Ca(2+), Boltzmann fits to the data yielded V(1/2) and slope factors of -39.6 mV and 10.0 for inactivation and 2.8 mV and 7.7 for activation. In Ba(2+), V(1/2) and slope factors were -29.2 mV and 9.2 for inactivation and -5.6 mV and 6.1 for activation. Neither calciseptine (10 nM), mibefradil (1 μM), nor ω-agatoxin IVA (20 and 100 nM) blocked basal Ba(2+) currents. Calciseptine (10 nM) and mibefradil (1 μM) also failed to reverse ANG II-induced DVR vasoconstriction, although raising mibefradil concentration to 10 μM was partially effective. We conclude that DVR pericytes predominantly express voltage-gated divalent currents that are carried by L-type channels.
• Dialysis Reduces Portal Pressure in Patients with Chronic Hepatitis C Artificial Organs. Jul, 2010  |   Pubmed ID: 20653650 The purpose of this study was to characterize changes in hepatic venous pressures in patients with chronic hepatitis C. The histology and laboratory data from patients with chronic hepatitis C who underwent a transjugular liver biopsy (TJLB) and hepatic venous pressure gradient measurement were analyzed. Portal hypertension was defined as hepatic venous pressure gradient > or =6 mm Hg. A single pathologist masked to hepatic venous pressure gradient scored liver sections for inflammation and fibrosis. The patients with high-grade inflammation (relative risk [RR] 2.82, P = 0.027, multivariate analysis) and late-stage fibrosis (RR 2.81, P = 0.022) were more likely to have a hepatic venous pressure gradient > or =6 mm Hg, while the patients on dialysis (RR 0.32, P = 0.01) were less likely to have a hepatic venous pressure gradient > or =6 mm Hg. The patients on dialysis (n = 58) had an elevated serum blood urea nitrogen and creatinine when compared with those who were not (n = 75) (47.6 +/- 3.3 and 7.98 +/- 0.4 vs. 25.9 +/- 2.0 and 1.66 +/- 0.22 mg/dL, respectively; P < 0.001). While the hepatic venous pressure gradient increased with the rising levels of liver fibrosis in the latter group (P < 0.01), it did not change in the patients on dialysis (P = 0.41). The median hepatic venous pressure gradient was especially low in late-stage fibrosis patients on dialysis when compared with the latter group (5 vs. 10 mm Hg, P = 0.017). In patients on dialysis, serum transaminases were low across all levels of fibrosis. Twenty-three of the 92 patients with early fibrosis had a hepatic venous pressure gradient > or =6 mm Hg. In patients with chronic hepatitis C, concomitant TJLB and hepatic venous pressure gradient measurement identify those who have early fibrosis and portal hypertension. Long-term hemodialysis may reduce portal pressure in these patients.
• Descriptive Epidemiology of Equine Influenza in India (2008-2009): Temporal and Spatial Trends Veterinaria Italiana. Oct-Dec, 2010  |   Pubmed ID: 21120800 Equine influenza is a contagious viral disease that affects all members of the family Equidae, i.e., horses, donkeys and mules. The authors describe the pattern of equine influenza outbreaks in a number of states of India from July 2008 to June 2009. The disease was first reported in June 2008 in Katra (Jammu and Kashmir) and spread to ten other states within a year. All outbreaks of equine influenza in the various states were confirmed by laboratory investigations (virus isolation and/or serological confirmation based on haemagglutination inhibition [HI] assays of paired samples) before declaring them as equine influenza virus-affected state(s). The virus (H3N8) was reported from various locations in the country including Katra, Mysore (Karnataka), Ahmedabad (Gujarat), Gopeshwar and Uttarkashi (Uttarakhand) and was isolated in 9- to 11-day-old embryonated chicken eggs. The virus was confirmed as H3N8 by HI assays with standard serum and amplification of full-length haemagglutinin and neuraminidase genes by reverse transcriptase-polymerase chain reaction. Serum samples (n = 4 740) of equines from 13 states in India screened by HI revealed 1074 (22.65%) samples as being positive for antibodies to equine influenza virus (H3N8).
• In Vivo Magnetic Resonance Imaging to Detect Biliary Excretion of 19F-labeled Drug in Mice Drug Metabolism and Disposition: the Biological Fate of Chemicals. May, 2011  |   Pubmed ID: 21270105 Isoflurane is an inhaled halogenated hydrocarbon anesthetic commonly used for animal research. In our quest to develop a method for measuring bile acid transport in live animals using (19)F magnetic resonance (MR) imaging, it occurred to us that isoflurane, which contains five fluorines per molecule and is probably widely distributed, would provide an excellent test drug to evaluate the merits of this approach. Experiments in 20- to 28-g male C57BL/6 mice were performed using a horizontal bore scanner with a 30-mm (19)F/(1)H dual-tuned surface coil used to transmit and receive radiofrequency signals at 300.28 MHz for (1)H and 282.55 MHz for (19)F nuclei. Proton MR imaging was used to identify the mouse gallbladder in vivo, which was verified by anatomical dissection. Subsequent experiments in mice inhaling 1.5% isoflurane for 1 to 2 h revealed robust (19)F signals from the gallbladder, verified by overlying (1)H and (19)F signals. No (19)F signal was detected in mice anesthetized with nonhalogenated anesthetics. The presence of isoflurane in gallbladder bile of isoflurane-treated mice was verified using liquid chromatography-mass spectrometry. Gallbladder bile isoflurane content ranged from 3.2 to 4.7 μg. The data presented here provide proof of concept that this novel approach can be used for in vivo measurement of biliary excretion of both existing and novel (19)F-labeled drugs.
• Muscarinic Receptor Agonists Stimulate Human Colon Cancer Cell Migration and Invasion American Journal of Physiology. Gastrointestinal and Liver Physiology. May, 2011  |   Pubmed ID: 21273532 Muscarinic receptors (CHRM) are overexpressed in colon cancer. To explore a role for muscarinic receptor signaling in colon cancer metastasis, we used human H508 and HT29 colon cancer cells that coexpress epidermal growth factor (ERBB) and CHRM3 receptors. In a wound closure model, following 8-h incubation of H508 cells with 100 μM ACh we observed a threefold increase in cell migration indistinguishable from the actions of epidermal growth factor (EGF). Atropine blocked the actions of ACh but not of EGF. In SNU-C4 colon cancer cells that express ERBB but not CHRM, EGF caused a threefold increase in migration; ACh had no effect. ACh-induced cell migration was attenuated by chemical inhibitors of ERBB1 activation, by anti-ERBB1 antibody, and by inhibitors of ERK and phosphatidylinositol 3-kinase (PI3K) signaling. Consistent with matrix metalloproteinase-7 (MMP7)-mediated release of an ERBB1 ligand, heparin binding epidermal growth factor-like growth factor (HBEGF), ACh-induced migration was inhibited by an MMP inhibitor and by anti-MMP7 and -HBEGF antibodies. ACh-induced cell migration was blocked by inhibiting RhoA and ROCK, key proteins that interact with the actin cytoskeleton. ACh-induced RhoA activation was attenuated by agents that inhibit ERBB1, ERK, and PI3K activation. Collectively, these findings indicate that ACh-induced cell migration is mediated by MMP7-mediated release of HBEGF, an ERBB ligand that activates ERBB1 and downstream ERK and PI3K signaling. In a cell invasion model, ACh-induced HT29 cell invasion was blocked by atropine. In concert with previous observations, these findings indicate that muscarinic receptor signaling plays a key role in colon cancer cell proliferation, survival, migration, and invasion.
• Muscarinic Receptor Subtype-3 Gene Ablation and Scopolamine Butylbromide Treatment Attenuate Small Intestinal Neoplasia in Apcmin/+ Mice Carcinogenesis. Sep, 2011  |   Pubmed ID: 21705482 M3 subtype muscarinic receptors (CHRM3) are over-expressed in colon cancer. In this study, we used Apc(min/+) mice to identify the role of Chrm3 expression in a genetic model of intestinal neoplasia, explored the role of Chrm3 in intestinal mucosal development and determined the translational potential of inhibiting muscarinic receptor activation. We generated Chrm3-deficient Apc(min/+) mice and compared intestinal morphology and tumor number in 12-week-old Apc(min/+)Chrm3(-/-) and Apc(min/+)Chrm3(+/+) control mice. Compared with Apc(min/+)Chrm3(+/+) mice, Apc(min/+)Chrm3(-/-) mice showed a 70 and 81% reduction in tumor number and volume, respectively (P < 0.01). In adenomas, β-catenin nuclear staining was reduced in Apc(min/+)Chrm3(-/-) compared with Apc(min/+)Chrm3(+/+) mice (P < 0.02). Whereas Apc gene mutation increased the number of crypt and Paneth cells and decreased villus goblet cells, these changes were absent in Apc(min/+)Chrm3(-/-) mice. To determine whether pharmacological inhibition of muscarinic receptor activation attenuates intestinal neoplasia, we treated 6-week-old Apc(min/+) mice with scopolamine butylbromide, a non-subtype-selective muscarinic receptor antagonist. After 8 weeks of continuous treatment, scopolamine butylbromide-treated mice showed a 22% reduction in tumor number (P = 0.027) and a 36% reduction in tumor volume (P = 0.004) as compared with control mice. Compared with Chrm3 gene ablation, the muscarinic antagonist was less efficacious, most probably due to shorter duration of treatment and incomplete blockade of muscarinic receptors. Overall, these findings indicate that interplay of Chrm3 and β-catenin signaling is important for intestinal mucosal differentiation and neoplasia and provide a proof-of-concept that pharmacological inhibition of muscarinic receptor activation can attenuate intestinal neoplasia in vivo.
• Bile Acids Regulate Cardiovascular Function Clinical and Translational Science. Jun, 2011  |   Pubmed ID: 21707953 Research over the last decade has uncovered roles for bile acids (BAs) that extend beyond their traditional functions in regulating lipid digestion and cholesterol metabolism. BAs are now recognized as signaling molecules that interact with both plasma membrane and nuclear receptors. Emerging evidence indicates that by interacting with these receptors, BAs regulate their own synthesis, glucose and energy homeostasis, and other important physiological events. Herein, we provide a comprehensive review of the actions of BAs on cardiovascular function. In the heart and the systemic circulation, BAs interact with plasma membrane G-protein-coupled receptors, for example, TGR5 and muscarinic receptors, and nuclear receptors, for example, the farnesoid (FXR) and pregnane (PXR) xenobiotic receptors. BA receptors are expressed in cardiovascular tissue, however, the mechanisms underlying BA-mediated regulation of cardiovascular function remain poorly understood. BAs reduce heart rate by regulating channel conductance and calcium dynamics in sino-atrial and ventricular cardiomyocytes and regulate vascular tone via both endothelium-dependent and -independent mechanisms. End-stage liver disease, obstructive jaundice, and intrahepatic cholestasis of pregnancy are prominent conditions in which elevated serum BAs alter vascular dynamics. This review focuses on BAs as newly recognized signaling molecules that modulate cardiovascular function.
• Distance from Skin to Epidural Space: Correlation with Body Mass Index (BMI) Journal of Anaesthesiology, Clinical Pharmacology. Jan, 2011  |   Pubmed ID: 21804704 Epidural anaesthesia is being increasingly used to provide anaesthesia for surgery on the lower abdomen, perineum and lower extremities. However success of the epidural technique depends upon the correct identification of epidural space.2 We conducted a study to find the distance from skin to the epidural space and its correlation with body mass index, to improve the success rate.
• Liver Infarction After Transjugular Intrahepatic Portosystemic Shunt in a Liver Transplant Recipient Hepatology (Baltimore, Md.). Nov, 2011  |   Pubmed ID: 21932409
• Muscarinic Receptor Agonists Stimulate Matrix Metalloproteinase 1-dependent Invasion of Human Colon Cancer Cells Biochemical and Biophysical Research Communications. Nov, 2011  |   Pubmed ID: 22027145 Mammalian matrix metalloproteinases (MMPs) which degrade extracellular matrix facilitate colon cancer cell invasion into the bloodstream and extra-colonic tissues; in particular, MMP1 expression correlates strongly with advanced colon cancer stage, hematogenous metastasis and poor prognosis. Likewise, muscarinic receptor signaling plays an important role in colon cancer; muscarinic receptors are over-expressed in colon cancer compared to normal colon epithelial cells. Muscarinic receptor activation stimulates proliferation, migration and invasion of human colon cancer cells. In mouse intestinal neoplasia models genetic ablation of muscarinic receptors attenuates carcinogenesis. In the present work, we sought to link these observations by showing that MMP1 expression and activation plays a mechanistic role in muscarinic receptor agonist-induced colon cancer cell invasion. We show that acetylcholine, which robustly increases MMP1 expression, stimulates invasion of HT29 and H508 human colon cancer cells into human umbilical vein endothelial cell monolayers - this was abolished by pre-incubation with atropine, a non-selective muscarinic receptor inhibitor, and by pre-incubation with anti-MMP1 neutralizing antibody. Similar results were obtained using a Matrigel chamber assay and deoxycholyltaurine (DCT), an amidated dihydroxy bile acid associated with colon neoplasia in animal models and humans, and previously shown to interact functionally with muscarinic receptors. DCT treatment of human colon cancer cells resulted in time-dependent, 10-fold increased MMP1 expression, and DCT-induced cell invasion was also blocked by pre-treatment with anti-MMP1 antibody. This study contributes to understanding mechanisms underlying muscarinic receptor agonist-induced promotion of colon cancer and, more importantly, indicates that blocking MMP1 expression and activation has therapeutic promise to stop or retard colon cancer invasion and dissemination.
• Effects of Deoxycholylglycine, a Conjugated Secondary Bile Acid, on Myogenic Tone and Agonist-induced Contraction in Rat Resistance Arteries PloS One. 2012  |   Pubmed ID: 22359652 Bile acids (BAs) regulate cardiovascular function via diverse mechanisms. Although in both health and disease serum glycine-conjugated BAs are more abundant than taurine-conjugated BAs, their effects on myogenic tone (MT), a key determinant of systemic vascular resistance (SVR), have not been examined.
• Design and Characterization of a Novel Fluorinated Magnetic Resonance Imaging Agent for Functional Analysis of Bile Acid Transporter Activity Pharmaceutical Research. May, 2013  |   Pubmed ID: 23319170 To synthesize a trifluorinated bile acid that can be used for (19)F magnetic resonance imaging (MRI) of bile acid enterohepatic circulation, characterize its in vitro transporter affinity, stability, and (19)F-MRI signal, and assess its ability to concentrate in the gallbladder of C57BL/6 mice.
• Effects of Modulating M3 Muscarinic Receptor Activity on Azoxymethane-induced Liver Injury in Mice Biochemical Pharmacology. Jul, 2013  |   Pubmed ID: 23707755 Previously, we reported that azoxymethane (AOM)-induced liver injury is robustly exacerbated in M3 muscarinic receptor (M3R)-deficient mice. We used the same mouse model to test the hypothesis that selective pharmacological modulation of M3R activity regulates the liver injury response. Initial experiments confirmed that giving a selective M3R antagonist, darifenacin, to AOM-treated mice mimicked M3R gene ablation. Compared to vehicle controls, mice treated with the M3R antagonist had reduced survival and increased liver nodularity and fibrosis. We next assessed AOM-induced liver injury in mice treated with a selective M3R agonist, pilocarpine. After pilocarpine treatment, stimulation of post-M3R signaling in the liver was evidenced by ERK and AKT activation. In contrast to the damaging effects of the M3R antagonist, administering pilocarpine to AOM-treated mice significantly attenuated hepatic stellate cell activation, collagen deposition, bile ductule proliferation, and liver fibrosis and nodularity. As anticipated from these findings, livers from pilocarpine-treated mice exhibited reduced expression of key players in fibrosis (α1 collagen, α-smooth muscle actin, TGF-β1, PGDF, TGF-β1R, PGDFR) and decreased mRNA levels for molecules that regulate extracellular matrix formation (TIMP-1, TIMP-2, MMP-2, MMP-13). Cleaved caspase-3, nitrotyrosine and BrdU immunostaining provided evidence that pilocarpine treatment reduced hepatocyte apoptosis and oxidative stress, while increasing hepatocyte proliferation. Collectively, these findings identify several downstream mechanisms whereby M3R activation ameliorates toxic liver injury. These novel observations provide a proof-of-principle that selectively stimulating M3R activation to prevent or diminish liver injury is a therapeutic strategy worthy of further investigation.
• Phrygian Cap Appearance of a Mouse Gallbladder on Magnetic Resonance Imaging Journal of Veterinary Science & Medical Diagnosis. Mar, 2013  |   Pubmed ID: 24371838 We used live-animal magnetic resonance imaging (MRI) to examine the gallbladders of male mice. These healthy mice were fasted overnight before the study and anesthetized in an animal chamber, with a gas mixture of oxygen and isoflurane for small animal MRI. In the course of these live-animal MRI studies, we observed a Phrygian cap appearance to the gallbladder of one healthy-appearing 6-week-old male mouse, similar to that of the human gallbladder described in many reports. After euthanasia for measurement of bile content, this mouse's gallbladder appeared anatomically normal. To our knowledge, this is the first report of a Phrygian cap appearance of the murine gallbladder.
• Dietary Fiber and Risk of Inflammatory Bowel Disease: Fact or Hype? Gastroenterology. Apr, 2014  |   Pubmed ID: 24576735
• Divergent Effects of Muscarinic Receptor Subtype Gene Ablation on Murine Colon Tumorigenesis Reveals Association of M3R and Zinc Finger Protein 277 Expression in Colon Neoplasia Molecular Cancer. 2014  |   Pubmed ID: 24694019 M3 and M1 subtype muscarinic receptors are co-expressed in normal and neoplastic intestinal epithelial cells. In mice, ablating Chrm3, the gene encoding M3R, robustly attenuates intestinal tumor formation. Here we investigated the effects of Chrm1 gene ablation, alone and in combination with Chrm3 ablation.
• In Vivo Performance of a Novel Fluorinated Magnetic Resonance Imaging Agent for Functional Analysis of Bile Acid Transport Molecular Pharmaceutics. May, 2014  |   Pubmed ID: 24708306 A novel trifluorinated cholic acid derivative, CA-lys-TFA, was designed and synthesized for use as a tool to measure bile acid transport noninvasively using magnetic resonance imaging (MRI). In the present study, the in vivo performance of CA-lys-TFA for measuring bile acid transport by MRI was investigated in mice. Gallbladder CA-lys-TFA content was quantified using MRI and liquid chromatography/tandem mass spectrometry. Results in wild-type (WT) C57BL/6J mice were compared to those in mice lacking expression of Asbt, the ileal bile acid transporter. (19)F signals emanating from the gallbladders of WT mice 7 h after oral gavage with 150 mg/kg CA-lys-TFA were reproducibly detected by MRI. Asbt-deficient mice administered the same dose had undetectable (19)F signals by MRI, and gallbladder bile CA-lys-TFA levels were 30-fold lower compared to WT animals. To our knowledge, this represents the first report of in vivo imaging of an orally absorbed drug using (19)F MRI. Fluorinated bile acid analogues have potential as tools to measure and detect abnormal bile acid transport by MRI.
• Are We Ready for Combination Therapy in Moderate-to-severe Ulcerative Colitis? Gastroenterology. Aug, 2014  |   Pubmed ID: 24976027
• Design and Evaluation of a Novel Trifluorinated Imaging Agent for Assessment of Bile Acid Transport Using Fluorine Magnetic Resonance Imaging Journal of Pharmaceutical Sciences. Nov, 2014  |   Pubmed ID: 25196788 Previously, we developed a trifluorinated bile acid, CA-lys-TFA, with the objective of noninvasively assessing bile acid transport in vivo using (19) F magnetic resonance imaging (MRI). CA-lys-TFA was successfully imaged in the mouse gallbladder, but was susceptible to deconjugation in vitro by choloylglycine hydrolase (CGH), a bacterial bile acid deconjugating enzyme found in the terminal ileum and colon. The objective of the present study was to develop a novel trifluorinated bile acid resistant to deconjugation by CGH. CA-sar-TFMA was designed, synthesized, and tested for in vitro transport properties, stability, imaging properties, and its ability to differentially accumulate in the gallbladders of normal mice, compared with mice with known impaired bile acid transport (deficient in the apical sodium-dependent bile acid transporter, ASBT). CA-sar-TFMA was a potent inhibitor and substrate of ASBT and the Na(+) /taurocholate cotransporting polypeptide. Stability was favorable in all conditions tested, including the presence of CGH. CA-sar-TFMA was successfully imaged and accumulated at 16.1-fold higher concentrations in gallbladders from wild-type mice compared with those from Asbt-deficient mice. Our results support the potential of using MRI with CA-sar-TFMA as a noninvasive method to assess bile acid transport in vivo.
• M1 Muscarinic Receptors Modify Oxidative Stress Response to Acetaminophen-induced Acute Liver Injury Free Radical Biology & Medicine. Jan, 2015  |   Pubmed ID: 25452146 The role of muscarinic receptor subtypes in modulating acute liver injury is unknown. We detected M1 muscarinic receptor (M1R) expression in human and murine hepatocytes, and investigated the consequences of M1R deficiency on acute liver injury in vivo and inhibiting M1R activation on hepatocyte injury in vitro. Age-matched wild-type (WT) and M1R-deficient (Chrm1(-/-)) male mice were injected intraperitoneally with 200mg/kg acetaminophen (APAP) and euthanized 0, 2, 4, 16, 24, and 36h later. Biochemical and histological parameters indicated that liver injury peaked within 16h after APAP treatment and resolved by 24h. Compared to WT, M1R-deficient mice had reduced intrahepatic hemorrhage and hepatocyte necrosis, reflected by an attenuated rise in serum alanine aminotransferase levels. Livers of M1R-deficient mice showed reduced hepatocyte DNA fragmentation and attenuated expression of injury cytokines (Il-1α, Il-1β, Il-6, and Fasl). In all mice hepatic glutathione levels decreased after APAP injection, but they recovered more quickly in M1R-deficient mice. During the course of APAP-induced liver injury in M1R-deficient compared to WT mice, hepatic Nrf-2, Gclc, and Nqo1 expressions increased and nitrotyrosine generation decreased. APAP metabolic pathways were not altered by M1R deficiency; expression of hepatic Cyp2e1, Cyp1a2, Cyp3a11, Cyp3a13, Car, and Pxr was similar in Chrm1(-/-) and WT mice. Finally, treatment of murine AML12 hepatocytes with a novel M1R antagonist, VU0255035, attenuated H2O2-induced oxidative stress, prevented GSH depletion, and enhanced viability. We conclude that M1R modify hepatocyte responses to oxidative stress and that targeting M1R has therapeutic potential for toxic liver injury.