wire-myography-for-dorsal-aorta-mesenteric-resistance-arteries-from

Wire Myography for Dorsal Aorta and Mesenteric Resistance Arteries from Mice and Rats

Wire myography is a widely used ex vivo technique for the quantitative assessment of vascular function in isolated arteries. Because large conduit and ...

University of Toledo, College of Medicine and Life Sciences

Sporadic occurrence of congenital portosystemic shunt (PSS) at a rate of ∼1 out of 10 among C57BL/6 J mice, which are widely used in biomedical research, results in aberrancies in serologic, metabolic, and physiologic parameters. Therefore, mice with PSS should be identified as outliers in research. Accordingly, we sought methods to, reliably and efficiently, identify PSS mice. Serum total bile acids ≥ 40 µm is a  biomarker of PSS in mice but utility of this biomarker is limited by its cost and invasiveness, particularly if large numbers of mice are to be screened. This led us to investigate if assay of urine might serve as a simple, inexpensive, noninvasive means of PSS diagnosis. Metabolome profiling uncovered that Krebs cycle intermediates, that is, citrate, α-ketoglutarate, and fumarate, were strikingly and distinctly elevated in the urine of PSS mice. We leveraged the iron-chelating and pH-lowering properties of such metabolites as the basis for 3 urine-based PSS screening tests: urinary iron-chelation assay, pH strip test, and phenol red assay. Our findings demonstrate the feasibility of using these colorimetric assays, whereby their readout can be assessed by direct observation, to diagnose PSS in an inexpensive, rapid, and noninvasive manner. Application of our urinary PSS screening protocols can aid biomedical research by enabling stratification of PSS mice, which, at present, likely confound numerous ongoing studies.

Urine-based Detection of Congenital Portosystemic Shunt in C57BL/6 Mice.

The single largest contributor to human mortality is cardiovascular disease, the top risk factor for which is hypertension (HTN). The last two decades have placed much emphasis on the identification of genetic factors contributing to HTN. As a result, over 1,500 genetic alleles have been associated with human HTN. Mapping studies using genetic models of HTN have yielded hundreds of blood pressure (BP) loci but their individual effects on BP are minor, which limits opportunities to target them in the clinic. The value of collecting genome-wide association data is evident in ongoing research, which is beginning to utilize these data at individual-level genetic disparities combined with artificial intelligence (AI) strategies to develop a polygenic risk score (PRS) for the prediction of HTN. However, PRS alone may or may not be sufficient to account for the incidence and progression of HTN because genetics is responsible for <30% of the risk factors influencing the etiology of HTN pathogenesis. Therefore, integrating data from other nongenetic factors influencing BP regulation will be important to enhance the power of PRS. One such factor is the composition of gut microbiota, which constitute a more recently discovered important contributor to HTN. Studies to-date have clearly demonstrated that the transition from normal BP homeostasis to a state of elevated BP is linked to compositional changes in gut microbiota and its interaction with the host. Here, we first document evidence from studies on gut dysbiosis in animal models and patients with HTN followed by a discussion on the prospects of using microbiota data to develop a metagenomic risk score (MRS) for HTN to be combined with PRS and a clinical risk score (CRS). Finally, we propose that integrating AI to learn from the combined PRS, MRS and CRS may further enhance predictive power for the susceptibility and progression of HTN.

Combating hypertension beyond genome-wide association studies: Microbiome and artificial intelligence as opportunities for precision medicine.

Dahl salt-sensitive (SS) rats fed a high-salt diet, but not low-salt, exhibit vascular dysfunction. Several substrains of SS rats exist that differ in their blood pressure phenotypes and salt sensitivity. The goal of this study was to investigate whether the John-Rapp-derived SS rat (SS/Jr), which exhibits spontaneous hypertension on a low-salt diet, presents with hallmarks of vascular dysfunction observed in another experimental model of hypertension independent of dietary salt, the spontaneously hypertensive rat (SHR). Endothelium-intact aortic rings and mesenteric resistance arteries were isolated from low-salt fed adult male SS/Jr rats and SHRs, or their respective controls, for isometric wire myography. Vessels were challenged with cumulative concentrations of various vasoactive substances, in the absence or presence of nitric oxide synthase or cyclooxygenase inhibitors. Despite showing some differences in their responses to various vasoactive substances, both SS/Jr rats and SHRs exhibited key features of vascular dysfunction, including endothelial dysfunction and hyperresponsiveness to vasocontractile agonists. In conclusion, this study provides evidence to support the utility of the SS/Jr rat strain maintained on a low-salt diet as a valid experimental model for vascular dysfunction, a key feature of human hypertension.

Spontaneous vascular dysfunction in Dahl salt-sensitive male rats raised without a high-salt diet.

Gut microbiota dysbiosis is linked to vascular wall disease, but the mechanisms by which gut microbiota cross-talk with the host vascular cells remain largely unknown. Shikimic acid (SA) is a biochemical intermediate synthesized in plants and microorganisms, but not mammals. Surprisingly, recent metabolomic profiling data demonstrate that SA is detectable in human and murine blood. In this study, analyzing data from germ-free rats, we provide evidence in support of SA as a bona fide gut microbiota-derived metabolite, emphasizing its biological relevance. Since vascular cells are the first cells exposed to circulating metabolites, in this study, we examined, for the first time, the effects and potential underlying molecular mechanisms of SA on vascular smooth muscle cell (VSMC) proliferation and migration, which play a key role in occlusive vascular diseases, such as post-angioplasty restenosis and atherosclerosis. We found that SA inhibits the proliferation and migration of human coronary artery SMCs. At the molecular level, unexpectedly, we found that SA activates, rather than inhibits, multiple pro-mitogenic signaling pathways in VSMCs, such as ERK1/2, AKT, and mTOR/p70S6K. Conversely, we found that SA activates the anti-proliferative AMP-activated protein kinase (AMPK) in VSMCs, a key cellular energy sensor and regulator. However, loss-of-function experiments demonstrate that AMPK does not mediate the inhibitory effects of SA on VSMC proliferation. In conclusion, these studies demonstrate that a microbiota-derived metabolite, SA, inhibits VSMC proliferation and migration in vitro and prompt further evaluation of the possible underlying molecular mechanisms and the potential protective role in VSMC-related vascular wall disease in vivo.

Article	Year
Urine-based Detection of Congenital Portosystemic Shunt in C57BL/6 Mice. Function (Oxford, England)\| PubMed ID: 37575479	2023
Combating hypertension beyond genome-wide association studies: Microbiome and artificial intelligence as opportunities for precision medicine. Cambridge prisms. Precision medicine\| PubMed ID: 38550938	2023
Spontaneous vascular dysfunction in Dahl salt-sensitive male rats raised without a high-salt diet. Physiological reports\| PubMed ID: 39048525	2024
Gut microbiota-derived Metabolite, Shikimic Acid, inhibits vascular smooth muscle cell proliferation and migration. Biochemical pharmacology\| PubMed ID: 39251142	2024
Novel role of vascular smooth muscle cell-expressed METTL3 in atherosclerosis. Cardiovascular research\| PubMed ID: 40037572	2025

Islam Osman

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