Commensal microbiota within a holobiont contribute to the overall health of the host via mutualistic symbiosis. Disturbances in such symbiosis is prominently correlated with a variety of diseases affecting the modern society of humans including cardiovascular diseases, which are the number one contributors to human mortality. Given that a hallmark of all cardiovascular diseases is changes in vascular function, we hypothesized that depleting microbiota from a holobiont would induce vascular dysfunction. To test this hypothesis, young mice of both sexes raised in germ-free conditions were examined vascular contractility and structure. Here we observed that male and female germ-free mice presented a decrease in contraction of resistance arteries. These changes were more pronounced in germ-free males than in germ-free females mice. Furthermore, there was a distinct change in vascular remodeling between males and females germ-free mice. Resistance arteries from male germ-free mice demonstrated increased vascular stiffness, as shown by the leftward shift in the stress-strain curve and inward hypotrophic remodeling, a characteristic of chronic reduction in blood flow. On the other hand, resistance arteries from germ-free female mice were similar in the stress-strain curves to that of conventionally raised mice, but were distinctly different and showed outward hypertrophic remodeling, a characteristic seen in aging.

Cell death has long been a characteristic phenotype of organ damage in hypertension, and recently, leaky gut has been revealed as a novel hypertensive phenotype. However, despite the increase in bacterial and damaged mitochondrial products in the circulation of hypertensive patients and animals, the mechanistic contribution of these two phenomena to hypertension pathophysiology is unknown. Mitochondria and bacteria both start protein translation with an N-formyl methionine residue and thus are the only sources of NFPs (N-formyl peptides), which activate the FPR-1 (formyl peptide receptor-1). We hypothesized that the synergistic action of bacterial and mitochondrial NFPs would cause the spontaneous elevation of blood pressure and vascular remodeling in male Dahl salt-sensitive rats via FPR-1. We observed that mitochondria-derived peptides originating from cell death in the kidneys are responsible for FPR-1–induced vascular hypercontractility and remodeling and premature elevation of BP in Dahl salt-sensitive rats fed a low-salt diet. However, a high-salt diet leads to gut barrier disruption and, subsequently, a synergistic action of mitochondria, and bacteria-derived leaky gut NFPs lead to a severe and established hypertension. Administration of an FPR-1 antagonist lowered blood pressure in Dahl salt-sensitive rats on a low-salt diet but amoxicillin administration did not. These results reveal for the first time that cell death can be a cause of hypertensive pathophysiology, whereas leaky gut is a consequence.

Exercise capacity is a strong predictor of all-cause morbidity and mortality in humans. However, the associated hemodynamic traits that link this valuable indicator to its subsequent disease risks are numerable. Additionally, exercise capacity has a substantial heritable component and genome-wide screening indicates a vast amount of nuclear and mitochondrial DNA markers are significantly associated with traits of physical performance. A long-term selection experiment in rats confirms a divide for cardiovascular risks between low- and high-capacity runners (LCR and HCR, respectively), equipping us with a preclinical animal model to uncover new mechanisms. Here, we evaluated the LCR and HCR rat model system for differences in vascular function at the arterial resistance level. Consistent with the known divide between health and disease, we observed that LCR rats present with resistance artery and perivascular adipose tissue dysfunction compared to HCR rats that mimic qualities important for health, including improved vascular relaxation. Uniquely, we show by generating conplastic strains, that LCR males with mitochondrial DNA (mtDNA) of female HCR (LCR-mtHCR/Tol) present with improved vascular function. Conversely, HCR-mtLCR/Tol rats displayed indices for cardiac dysfunction. The outcome of this study suggests that the interplay between the nuclear genome and the maternally inherited mitochondrial genome with high intrinsic exercise capacity is a significant factor for improved vascular physiology, and animal models developed on an interaction between nuclear and mitochondrial DNA are valuable new tools for probing vascular risk factors in the offspring.

Exercise is a primary lifestyle intervention to control cardiovascular diseases such as hypertension. Exercise capacity and its health benefits are inheritable. However, the mechanisms by which exercise capacity differences influence overall health state remain unclear. We first hypothesized that low and high intrinsic exercise capacity lead to distinct heart weight and vascular function. Animal model (male, 20-24-weeks old, n = 6): heterogeneous stock selectively bred for over 20 years to produce low-capacity running rats (LCR) and high-capacity running rats (HCR), and an intrinsic control, high response trainer rats (HRT, control). Statistics: t-test: *p<0.05. Left ventricular (LV) weight was normalized by tibia length. We observed that HCR presented with LV hypertrophy compared to LCR and control (Control: 0.0155 ± 0.0006 vs. HCR: 0.0192 ± 0.0007* vs. LCR: 0.0164 ± 0.0004). Performing wire myography with 3 rd -order mesenteric resistance arteries (MRA), we observed that LCR MRA had an impaired maximum relaxation response (E max ) to acetylcholine (ACh) compared to HCR and control (Control: 94.99 ± 1.79 vs. HCR: 93.49 ± 12.17 vs. LCR: 72.95 ± 12.40*). Next, we questioned if these differences were the result of mitochondria. We used two reciprocal conplastic strains created by utilizing maternal mitochondrial inheritance (male, 30-36-weeks old, n = 4): LCR nuclear genome with HCR mitochondria (LCR.HCR mt ) and the reciprocal HCR.LCR mt . We observed that LCR.HCR mt presented with LV hypertrophy compared to LCR (0.0195 ± 0.0002* vs 0.0164 ± 0.0004) while HCR.LCR mt abolished HCR LV hypertrophy (0.0151 ± 0.0002* vs. 0.0192 ± 0.0007). Interestingly, in a separate group of animals (n = 4 - 5), LCR had higher mean arterial pressure (MAP) compared to HCR, and LCR.HCR mt had reduced MAP compared to LCR (LCR: 119 ± 2 vs. LCR.HCR mt : 111 ± 1*). No changes were observed in HCR.LCR mt compared to HCR. Further, LCR.HCR mt MRA presented with improved E max to ACh compared to LCR MRA (LCR: 72 ± 12 vs. LCR.HCR mt : 93 ± 2*) while no changes were observed in HCR.LCR mt MRA compared to HCR MRA. Overall, we conclude that intrinsic exercise capacity is directly proportional to cardiovascular effects. Similar to the nuclear genome, mitochondria are the key to this hereditary predisposition.

AimsChronic activation of the immune system contributes to kidney injury and hypertension. Mitochondria carry hallmarks of their bacterial ancestry and thus have emerged as a significant source of inflammatogenic damage‐associated molecular patterns. One of these hallmarks is that they still use formylated peptides (NFPs) as an initiator of protein synthesis. NFPs activate formyl peptide receptor (FPR), a G‐protein coupled receptor, and leads to receptor internalization and desensitization. We have observed that mitochondrial NFPs are elevated in the circulation of spontaneously hypertensive rats (SHR) and FPR blockage decreases blood pressure in this strain. Also, we and others observed that FPR downregulates upon activation in immune and non‐immune cells. Given that cell death and gut dysbiosis are present in salt sensitive hypertension, we hypothesized that Dahl sensitive rats would have decreased FPR expression, and that the decrease could be attributed to increased plasma levels of circulating mitochondria and/or bacteria NFPs from the cell death and leaky gut, respectively, and contributes to hypertension. Sex differences were also investigated.MethodsMale and Female Dahl Sensitive (S) and Resistant (R) rats (6‐week old) were given a low (0.3% NaCl) or high salt diet (2% NaCl) for 38 days. Rats received normal drinking water or water supplemented with neomycin (0.5 g/l, GIBCO) for 3 weeks. Kidney samples were taken from all rats and used for mRNA extraction and purification. The mRNA was made into cDNA to test gene expression for FPR. Blood was collected to measure mitochondrial NFPs. T‐test *p<0.05; n= 8–11 for Dahl S and R; n=7 for Dahl + neomycin.Results and ConclusionFPR expression was downregulated 4‐fold from male and female Dahl S when compared to Dahl R (AU: FPR mRNA: Dahl R 4.5 ± 1.3 vs. Dahl S: 0.7 ± 0.2*) (Figure 1). This phenomenon was independent of salt and sex differences. Antibiotic treatment partially restored FPR expression from Dahl S animals when compared to Dahl S treated with neomycin (AU FPR mRNA: Dahl S 4.5 ± 1.3 vs. Dahl S‐neomycin treated: 2.74 ± 0.99*). ND6, a mitochondrial protein, is 1.7‐fold higher in plasma from Dahl S compared to Dahl R. Unexpected, salt diet did not change this parameter. We have observed for the first time that FPR is downregulated in Dahl animals independent of salt probably due to overstimulation of this receptor. Therefore, FPR activation due to increased levels of bacterial (NFPs) could be associated with the development of renal injury at an early age independently of salt and elevations in arterial pressure.Support or Funding InformationAmerican Heart Association (18POST34060003) and National Institutes of Health (K99GM118885 and R01HL143082)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.