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In JoVE (1)
Other Publications (15)
- American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
- Pathophysiology : the Official Journal of the International Society for Pathophysiology / ISP
- American Journal of Physiology. Heart and Circulatory Physiology
- Microcirculation (New York, N.Y. : 1994)
- Microcirculation (New York, N.Y. : 1994)
- Microcirculation (New York, N.Y. : 1994)
- Journal of Applied Physiology (Bethesda, Md. : 1985)
- Physiological Genomics
- BMC Oral Health
- Journal of Dental Hygiene : JDH / American Dental Hygienists' Association
- Journal of Inflammation (London, England)
- Journal of Vascular Research
- Experimental Physiology
- American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
- Research Report (Health Effects Institute)
Articles by Adam G. Goodwill in JoVE
JoVE General
The ex vivo Isolated Skeletal Microvessel Preparation for Investigation of Vascular Reactivity
An ex vivo preparation is described for isolation of the largest gracilis muscle resistance arterioles for interrogation of both vascular responses to vasoactive stimuli and the assessment of basic structural properties via passive wall mechanics.
Other articles by Adam G. Goodwill on PubMed
Altered Mechanisms of Endothelium-dependent Dilation in Skeletal Muscle Arterioles with Genetic Hypercholesterolemia
With most cardiovascular disease risk factors, endothelium-dependent dilation of skeletal muscle resistance arterioles is compromised, although with hypercholesterolemia, impairments to reactivity are not consistently observed. Using apolipoprotein E (ApoE) and low-density lipoprotein receptor (LDLR) gene deletion male mouse models of hypercholesterolemia at 20 wk of age, we tested the hypothesis that arteriolar dilation would be maintained due to an increased stimulus-induced production of dilator metabolites via cyclooxygenase and cytochrome P-450 epoxygenase pathways. Arterioles from both strains demonstrated mild reductions in dilation to hypoxia and acetylcholine versus responses in C57/Bl/6J (C57) controls. However, although inhibition of nitric oxide synthase (NOS) attenuated dilation in arterioles from C57 controls, this effect was absent in ApoE or LDLR strains. In contrast, cyclooxygenase-dependent portions of dilator reactivity were maintained across the three strains. Notably, although combined NOS and cyclooxygenase inhibition abolished arteriolar responses to hypoxia and acetylcholine in C57 controls, significant reactivity remained in ApoE and LDLR strains. Whereas inhibition of cytochrome P-450 omega-hydroxylase and epoxygenases had no effect on this residual reactivity in ApoE and LDLR strains, inhibition of 12/15-lipoxygenase with nordihydroguaiaretic acid abolished the residual reactivity. With both hypoxic and methacholine challenges, arteries from ApoE and LDLR strains demonstrated an increased production of both 12(S)- and 15(S)-hydroxyeicosatetraenoic acid, end products of arachidonic acid metabolism via 12/15-lipoxygenase, a response that was not present in C57 controls. These results suggest that with development of hypercholesterolemia, mechanisms contributing to dilator reactivity in skeletal muscle arterioles are modified such that net reactivity to endothelium-dependent stimuli is largely intact.
Obesity and Vascular Dysfunction
One of the most profound challenges facing public health and public health policy in Western society is the increased incidence and prevalence of both overweight and obesity. While this condition can have significant consequences for patient mortality and quality of life, it can be further exacerbated as overweight/obesity can be a powerful stimulus for the development of additional risk factors for a negative cardiovascular outcome, including increased insulin resistance, dyslipidemia and hypertension. This manuscript will present the effects of systemic obesity on broad issues of vascular function in both afflicted human populations and in the most relevant animal models. Among the topics that will be covered are alterations to vascular reactivity (both dilator and constrictor responses), adaptations in microvascular network and vessel wall structure, and alterations to the patterns of tissue/organ perfusion as a result of the progression of the obese condition. Additionally, special attention will be paid to the contribution of chronic inflammation as a contributor to alterations in vascular function, as well as the role of perivascular adipose tissue in terms of impacting vessel behavior. When taken together, it is clearly apparent that the development of the obese condition can have profound, and frequently difficult to predict, impacts on integrated vascular function. Much of this complexity appears to have its basis in the extent to which other co-morbidities associated with obesity (e.g., insulin resistance) are present and exert contributing effects.
Increased Vascular Thromboxane Generation Impairs Dilation of Skeletal Muscle Arterioles of Obese Zucker Rats with Reduced Oxygen Tension
This study determined if altered vascular prostacyclin (PGI(2)) and/or thromboxane A(2) (TxA(2)) production with reduced Po(2) contributes to impaired hypoxic dilation of skeletal muscle resistance arterioles of obese Zucker rats (OZRs) versus lean Zucker rats (LZRs). Mechanical responses were assessed in isolated gracilis muscle arterioles following reductions in Po(2) under control conditions and following pharmacological interventions inhibiting arachidonic acid metabolism and nitric oxide synthase and alleviating elevated vascular oxidant stress. The production of arachidonic acid metabolites was assessed using pooled arteries from OZRs and LZRs in response to reduced Po(2). Hypoxic dilation, endothelium-dependent in both strains, was attenuated in OZRs versus LZRs. Nitric oxide synthase inhibition had no significant impact on hypoxic dilation in either strain. Cyclooxygenase inhibition dramatically reduced hypoxic dilation in LZRs and abolished responses in OZRs. Treatment of arterioles from OZRs with polyethylene glycol-superoxide dismutase improved hypoxic dilation, and this improvement was entirely cyclooxygenase dependent. Vascular PGI(2) production with reduced Po(2) was similar between strains, although TxA(2) production was increased in OZRs, a difference that was attenuated by treatment of vessels from OZRs with polyethylene glycol-superoxide dismutase. Both blockade of PGH(2)/TxA(2) receptors and inhibition of thromboxane synthase increased hypoxic dilation in OZR arterioles. These results suggest that a contributing mechanism underlying impaired hypoxic dilation of skeletal muscle arterioles of OZRs may be an increased vascular production of TxA(2), which competes against the vasodilator influences of PGI(2). These results also suggest that the elevated vascular oxidant stress inherent in metabolic syndrome may contribute to the increased vascular TxA(2) production and may blunt vascular sensitivity to PGI(2).
Increased Arachidonic Acid-induced Thromboxane Generation Impairs Skeletal Muscle Arteriolar Dilation with Genetic Dyslipidemia
The aim of this study was to determine if arachidonic acid (AA)-induced skeletal muscle arteriolar dilation is altered with hypercholesterolemia in ApoE and low-density lipoprotein receptor (LDLR) gene deletion mice fed a normal diet. This study also determined contributors to altered AA-induced dilation between dyslipidemic mice and controls, C57/Bl/6J (C57).
Impact of Chronic Anticholesterol Therapy on Development of Microvascular Rarefaction in the Metabolic Syndrome
The obese Zucker rat (OZR) model of the metabolic syndrome is partly characterized by moderate hypercholesterolemia, in addition to other contributing comorbidities. Previous results suggest that vascular dysfunction in OZR is associated with chronic reduction in vascular nitric-oxide (NO) bioavailability and chronic inflammation, both frequently associated with hypercholesterolemia. As such, we evaluated the impact of chronic cholesterol-reducing therapy on the development of impaired skeletal muscle arteriolar reactivity and microvessel density in OZR and its impact on chronic inflammation and NO bioavailability.
Differential Impact of Familial Hypercholesterolemia and Combined Hyperlipidemia on Vascular Wall and Network Remodeling in Mice
Genetic familial hypercholesterolemia (FH) and combined hyperlipidemia (FCH) are characterized by elevated plasma low-density lipoprotein (LDL) (FH) and LDL/triglycerides (FCH), with mouse models represented by LDL receptor (LDLR) and apolipoprotein E (ApoE) gene deletion mice, respectively. Given the impact of FH and FCH on health outcomes, we determined the impact of FH/FCH on vascular structure in LDLR and ApoE mice. LDLR, ApoE and control mice were utilized at 12-13 and 22-23 weeks when gracilis arteries were studied for wall mechanics and gastrocnemius muscles were harvested for microvessel density measurements. Conduit arteries and plasma samples were harvested for biochemical analyses. Arteries from ApoE and LDLR exhibited blunted expansion versus control, reduced distensibility and left-shifted stress versus strain relation (LDLR > ApoE). Microvessel density was reduced in ApoE and LDLR (ApoE > LDLR). Secondary analyses suggested that wall remodeling in LDLR was associated with cholesterol and MCP-1, while rarefaction in ApoE was associated with tumor necrosis factors-alpha, triglycerides and vascular production of TxA(2). Remodeling in ApoE and LDLR appears distinct; as that in LDLR is preferential for vascular walls, while that for ApoE is stronger for rarefaction. Remodeling in LDLR may be associated with cellular adhesion, while that in ApoE may be associated with pro-apoptotsis and constrictor prostanoid generation.
Depressive Behavior and Vascular Dysfunction: a Link Between Clinical Depression and Vascular Disease?
As chronic stress and depression have become recognized as significant risk factors for peripheral vascular disease in patients with no prior history of vasculopathy, we interrogated this relationship utilizing an established mouse model of chronic stress/depressive symptoms from behavioral research. Male mice were exposed to 8 wk of unpredictable chronic mild stress (UCMS; e.g., wet bedding, predator sound/smell, random disruption of light/dark cycle), with indexes of depressive behavior (coat status, grooming, and mobility) becoming exacerbated vs. controls. In vascular rings, constrictor (phenylephrine) and endothelium-independent dilator (sodium nitroprusside) responses were not different between groups, although endothelium-dependent dilation (methacholine) was attenuated with UCMS. Nitric oxide synthase (NOS) inhibition was without effect in UCMS but nearly abolished reactivity in controls, while cyclooxygenase inhibition blunted dilation in both. Combined blockade abolished reactivity in controls, although a significant dilation remained in UCMS that was abolished by catalase. Arterial NO production was attenuated by UCMS, although H2O2 production was increased. UCMS mice demonstrated an increased, although variable, insulin resistance and inflammation. However, while UCMS-induced vascular impairments were consistent, the predictive power of aggregate plasma levels of insulin, TNF-alpha, IL-1beta, and C-reactive peptide were limited. However, when separated into tertiles with regard to vascular outcomes, insulin resistance and hypertension were predictive of the most severe vascular impairments. Taken together, these data suggest that aggregate insulin resistance, inflammation, and hypertension in UCMS mice are not robust predictors of vascular dysfunction, suggesting that unidentified mechanisms may be superior predictors of poor vascular outcomes in this model.
Aspirin Resistance with Genetic Dyslipidemia: Contribution of Vascular Thromboxane Generation
One clinical intervention against the negative outcomes associated with atherothrombotic vascular disease (AVD) is low-dose, chronic aspirin therapy. However, epidemiological studies suggest that recurrence of adverse vascular events with aspirin therapy is growing and associated with therapy duration. The contributors to this outcome are unclear and include poor patient compliance and aspirin-resistant platelet thromboxane A(2) (TxA(2)) production. Based on previous results in hypercholesterolemic mice, we hypothesized that elevated aspirin-insensitive arachidonic acid (AA)-induced TxA(2) production by the vascular endothelium contributes to aspirin resistance in AVD independent of platelet behavior. AA-induced dilation was blunted in aortic rings and in arterioles from apolipoprotein E (ApoE) and low-density lipoprotein receptor (LDLR) gene deletion mice (vs. C57/Bl6/J), partially due to elevated TxA(2) production. Acute inhibition of cyclooxygenases or TxA(2) synthase attenuated the increased TxA(2) production in ApoE and LDLR and improved AA-induced dilation, responses that were mirrored by chronic treatment with low-dose aspirin of 16 wk duration. However, this effect was not temporally stable, and, with longer-duration therapy, the beneficial impact of aspirin on outcomes diminished. A similar, though less robust, pattern to the impact of chronic aspirin therapy on vascular outcomes was identified with chronic antioxidant treatment (TEMPOL). These results suggest that in dyslipidemic mice, the beneficial impact of chronic aspirin therapy on improving vascular outcomes decay with time and that a contributing element to subsequent negative vascular events may be the development of aspirin-resistant TxA(2) production by the vasculature itself.
Self-reported Dental Hygiene, Obesity, and Systemic Inflammation in a Pediatric Rural Community Cohort
A growing body of epidemiologic evidence links oral health, obesity, and cardiovascular health, though few studies have reported on these relationships in children. While underlying mechanisms are unclear, adult studies have suggested sub-acute systemic inflammation, also implicated in the etiology of both obesity and cardiovascular disease. This study investigated associations between self-reported dental hygiene, obesity, and systemic inflammation in children.
Association Between Dental Hygiene, Cardiovascular Disease Risk Factors and Systemic Inflammation in Rural Adults
A growing body of epidemiologic evidence links oral health, periodontal disease and cardiovascular health. While underlying pathophysiologic mechanisms are unclear, several studies have suggested a sub-acute inflammatory state, also implicated in the etiology of cardiovascular disease. The objective of the current study was to investigate associations between self-reported dental hygiene (brushing, flossing, preventive care and overall dental health), cardiovascular disease risk factors and systemic inflammation.
Hypercholesterolemia and Microvascular Dysfunction: Interventional Strategies
Hypercholesterolemia is defined as excessively high plasma cholesterol levels, and is a strong risk factor for many negative cardiovascular events. Total cholesterol levels above 200 mg/dl have repeatedly been correlated as an independent risk factor for development of peripheral vascular (PVD) and coronary artery disease (CAD), and considerable attention has been directed toward evaluating mechanisms by which hypercholesterolemia may impact vascular outcomes; these include both results of direct cholesterol lowering therapies and alternative interventions for improving vascular function. With specific relevance to the microcirculation, it has been clearly demonstrated that evolution of hypercholesterolemia is associated with endothelial cell dysfunction, a near-complete abrogation in vascular nitric oxide bioavailability, elevated oxidant stress, and the creation of a strongly pro-inflammatory condition; symptoms which can culminate in profound impairments/alterations to vascular reactivity. Effective interventional treatments can be challenging as certain genetic risk factors simply cannot be ignored. However, some hypercholesterolemia treatment options that have become widely used, including pharmaceutical therapies which can decrease circulating cholesterol by preventing either its formation in the liver or its absorption in the intestine, also have pleiotropic effects with can directly improve peripheral vascular outcomes. While physical activity is known to decrease PVD/CAD risk factors, including obesity, psychological stress, impaired glycemic control, and hypertension, this will also increase circulating levels of high density lipoprotein and improving both cardiac and vascular function. This review will provide an overview of the mechanistic consequences of the predominant pharmaceutical interventions and chronic exercise to treat hypercholesterolemia through their impacts on chronic sub-acute inflammation, oxidative stress, and microvascular structure/function relationships.
Growth-dependent Changes in the Contribution of Carbon Monoxide to Arteriolar Function
Endothelium-dependent dilation of skeletal muscle arterioles is mediated by unknown factors in very young rats. We assessed the possible contribution of carbon monoxide (CO) to this dilation and to dilation in older animals.
Divergence Between Arterial Perfusion and Fatigue Resistance in Skeletal Muscle in the Metabolic Syndrome
The metabolic syndrome is associated with elevated peripheral vascular disease risk, characterized by mismatched blood flow delivery/distribution and local metabolism. The obese Zucker rat (OZR) model of the metabolic syndrome exhibits myriad vascular impairments, although their integrated impact on functional hyperaemia remains unclear. In this study, arterial pressor responses and skeletal muscle perfusion were assessed in lean Zucker rats (LZRs) and OZRs during adrenergic stimulation (phenylephrine), challenge with thromboxane (U46619) and endothelium-dependent dilatation (methacholine). The OZRs were hypertensive compared with the LZRs, but this was abolished by adrenoreceptor blockade (phentolamine); pressor responses to U46619 were similar between strains and were abolished by blockade with the prostaglandin H(2)/thromboxane A(2) receptor antagonist, SQ-29548. Depressor reactivity to methacholine was impaired in OZRs, but was improved by antioxidant treatment (TEMPOL). Across levels of metabolic demand, blood flow to in situ gastrocnemius muscle was restrained by adrenergic constriction in OZRs, although this diminished with increased demand. Oxygen extraction, reduced in OZRs compared with LZRs across levels of metabolic demand, was improved by TEMPOL or SQ-29548; treatment with phentolamine did not impact extraction, and neither TEMPOL nor SQ-29548 improved muscle blood flow in OZRs. While oxygen uptake and muscle performance were consistently reduced in OZRs versus LZRs, treatment with all three agents improved outcomes, while treatment with individual agents was less effective. These results suggest that contributions of vascular dysfunction to perfusion, oxygen uptake and muscle performance are spatially distinct, with adrenergic constriction impacting proximal resistance and endothelial dysfunction impacting distal microvessel-tissue exchange. Further, these data suggest that increasing skeletal muscle blood flow in OZRs is not sufficient to improve performance, unless distal perfusion inhomogeneities are rectified.
Spatial Heterogeneity in Skeletal Muscle Microvascular Blood Flow Distribution is Increased in the Metabolic Syndrome
Previous studies have demonstrated that the metabolic syndrome is associated with impaired skeletal muscle arteriolar function, although integrating observations into a conceptual framework for impaired perfusion in peripheral vascular disease (PVD) has been limited. This study builds on previous work to evaluate in situ arteriolar hemodynamics in cremaster muscle of obese Zucker rats (OZR) to integrate existing knowledge into a greater understanding of impaired skeletal muscle perfusion. In OZR cremaster muscle, perfusion distribution at microvascular bifurcations (γ) was consistently more heterogeneous than in controls. However, while consistent, the underlying mechanistic contributors were spatially divergent as altered adrenergic constriction was the major contributor to altered γ at proximal microvascular bifurcations, with a steady decay with distance, while endothelial dysfunction was a stronger contributor in distal bifurcations with no discernible role proximally. Using measured values of γ, we found that simulations predict that successive alterations to γ in OZR caused more heterogeneous perfusion distribution in distal arterioles than in controls, an effect that could only be rectified by combined adrenoreceptor blockade and improvements to endothelial dysfunction. Intravascular (125)I-labeled albumin tracer washout from in situ gastrocnemius muscle of OZR provided independent support for these observations, indicating increased perfusion heterogeneity that was corrected only by combined adrenoreceptor blockade and improved endothelial function. These results suggest that a defining element of PVD in the metabolic syndrome may be an altered γ at microvascular bifurcations, that its contributors are heterogeneous and spatially distinct, and that interventions to rectify this negative outcome must take a new conceptual framework into account.
Pulmonary Particulate Matter and Systemic Microvascular Dysfunction
Pulmonary particulate matter (PM) exposure has been epidemiologically associated with an increased risk of cardiovascular morbidity and mortality, but the mechanistic foundations for this association are unclear. Exposure to certain types of PM causes changes in the vascular reactivity of several macrovascular segments. However, no studies have focused upon the systemic microcirculation, which is the primary site for the development of peripheral resistance and, typically, the site of origin for numerous pathologies. Ultrafine PM--also referred to as nanoparticles, which are defined as ambient and engineered particles with at least one physical dimension less than 100 nm (Oberdorster et al. 2005)--has been suggested to be more toxic than its larger counterparts by virtue of a larger surface area per unit mass. The purpose of this study was fourfold: (1) determine whether particle size affects the severity of postexposure microvascular dysfunction; (2) characterize alterations in microvascular nitric oxide (NO) production after PM exposure; (3) determine whether alterations in microvascular oxidative stress are associated with NO production, arteriolar dysfunction, or both; and (4) determine whether circulating inflammatory mediators, leukocytes, neurologic mechanisms, or a combination of these play a fundamental role in mediating pulmonary PM exposure and peripheral microvascular dysfunction. To achieve these goals, we created an inhalation chamber that generates stable titanium dioxide (TiO2) aerosols at concentrations up to 20 mg/m3. TiO2 is a well-characterized particle devoid of soluble metals. Sprague Dawley and Fischer 344 (F-344) rats were exposed to fine or nano-TiO2 PM (primary count modes of approximately 710 nm and approximately 100 nm in diameter, respectively) at concentrations of 1.5 to 16 mg/m3 for 4 to 12 hours to produce pulmonary loads of 7 to 150 microg in each rat. Twenty-four hours after pulmonary exposure, the following procedures were performed: the spinotrapezius muscle was prepared for in vivo microscopy, blood samples were taken from an arterial line, and various tissues were harvested for histologic and immunohistochemical analyses. Some rats received a bolus dose of cyclophosphamide 3 days prior to PM exposure to deplete circulating neutrophils and bronchoalveolar lavage (BAL) was performed in separate groups of rats exposed to identical TiO2 loads. No significant differences in BAL fluid composition based on PM size or load were found in these rats. Plasma levels of interleukin (IL)-2, IL-18, IL-13, and growth-related oncogene (GRO) (also known as keratinocyte-derived-chemokine [KC]) were altered after PM exposure. In rats exposed to fine TiO2, endothelium-dependent arteriolar dilation was significantly decreased, and this dysfunction was robustly augmented in rats exposed to nano-TiO2. This effect was not related to an altered smooth-muscle responsiveness to NO because arterioles in both groups dilated comparably in response to the NO donor sodium nitroprusside (SNP). Endogenous microvascular NO production was similarly decreased after inhalation of either fine or nano-TiO2 in a dose-dependent manner. Microvascular oxidative stress was significantly increased among both exposure groups. Furthermore, treatment with antioxidants (2,2,6,6-tetramethylpiperdine-N-oxyl [TEMPOL] plus catalase), the myeloperoxidase (MPO) inhibitor 4-aminobenzoic hydrazide (ABAH), or the nicotinamide adenine dinucleotide phosphate oxidase (NADPH oxidase) inhibitor apocynin partially restored NO production and normalized arteriolar function in both groups. Neutrophil depletion restored dilation in PM-exposed rats by as much as 42%. Coincubation of the spinotrapezius muscle with the fast sodium (Na+) channel antagonist tetrodotoxin (TTX) restored arteriolar dilation by as much as 54%, suggesting that sympathetic neural input may be affected by PM exposure. The results of these experiments indicate that (1) the size of inhaled PM dictates the intensity of systemic microvascular dysfunction; (2) this arteriolar dysfunction is characterized by a decreased bioavailability of endogenous NO; (3) the loss of bioavailable NO after PM exposure is at least partially caused by elevations in local oxidative stress, MPO activity, NADPH oxidase activity, or a combination of these responses; and (4) circulating neutrophils and sympathetic neurogenic mechanisms also appear to be involved in the systemic microvascular dysfunction that follows PM exposure. Taken together, these mechanistic studies support prominent hypotheses that suggest peripheral vascular effects associated with PM exposure are due to the activation of inflammatory mechanisms, neurogenic mechanisms, or both.
