Serotonin (5-hydroxytryptamine; 5-HT) delivered over 1 week results in a sustained fall in blood pressure in the sham and deoxycorticosterone acetate (DOCA)-salt rat. We hypothesized 5-HT lowers blood pressure through direct receptor-mediated vascular relaxation. In vivo, 5-HT reduced mean arterial pressure (MAP), increased heart rate, stroke volume, cardiac index, and reduced total peripheral resistance during a 1 week infusion of 5-HT (25 µg/kg/min) in the normotensive Sprague Dawley rat. The mesenteric vasculature was chosen as an ideal candidate for the site of 5-HT receptor mediated vascular relaxation given the high percentage of cardiac output the site receives. Real-time RT-PCR demonstrated that mRNA transcripts for the 5-HT_2B, 5-HT_1B, and 5-HT₇ receptors are present in sham and DOCA-salt superior mesenteric arteries. Immunohistochemistry and Western blot validated the presence of the 5-HT_2B, 5- HT_1B and 5-HT₇ receptor protein in sham and DOCA-salt superior mesenteric artery. Isometric contractile force was measured in endothelium-intact superior mesenteric artery and mesenteric resistance arteries in which the contractile 5- HT_2A receptor was antagonized. Maximum concentrations of BW-723C86 (5- HT_2B agonist), CP 93129 (5-HT_1B agonist) or LP-44 (5-HT₇ agonist) did not relax the superior mesenteric artery from DOCA-salt rats vs. vehicle. Additionally, 5-HT (10^–9 M to 10^–5 M) did not cause relaxation in either contracted mesenteric resistance arteries or superior mesenteric arteries from normotensive Sprague- Dawley rats. Thus, although 5-HT receptors known to mediate vascular relaxation are present in the superior mesenteric artery, they are not functional, and are therefore not likely involved in a 5-HT-induced fall in total peripheral resistance and MAP.

This study describes the atlas of cells in the thoracic aorta perivascular adipose tissue (taPVAT) of the Dahl-SS rat, an important hypertension model. We show that mechanotransducers are widely expressed in these cells. Moreover, PIEZO1 expression is shown to be restricted to the taPVAT and is functionally implicated in stress relaxation. These data will serve as the foundation for future studies investigating the role of taPVAT in this model of hypertensive disease.

Vascular tunicas synthesizing chemerin is a new finding. Vascular chemerin is independent of hepatic-derived chemerin. Vasculature from both males and females have resident chemerin. Chemerin1 receptor activity supports vascular tone.

Transglutaminases (TGs) are crosslinking enzymes best known for their vascular remodeling in hypertension. They require calcium to form an isopeptide bond, connecting a glutamine to a protein bound lysine residue or a free amine donor such as norepinephrine (NE) or serotonin (5-HT). We discovered that perivascular adipose tissue (PVAT) contains significant amounts of these amines, making PVAT an ideal model to test interactions of amines and TGs. We hypothesized that transglutaminases are active in PVAT. Real time RT-PCR determined that Sprague Dawley rat aortic, superior mesenteric artery (SMA), and mesenteric resistance vessel (MR) PVATs express TG2 and blood coagulation Factor-XIII (FXIII) mRNA. Consistent with this, immunohistochemical analyses support that these PVATs all express TG2 and FXIII protein. The activity of TG2 and FXIII was investigated in tissue sections using substrate peptides that label active TGs when in a catalyzing calcium solution. Both TG2 and FXIII were active in rat aortic PVAT, SMAPVAT, and MRPVAT. Western blot analysis determined that the known TG inhibitor cystamine reduced incorporation of experimentally added amine donor 5-(biotinamido)pentylamine (BAP) into MRPVAT. Finally, experimentally added NE competitively inhibited incorporation of BAP into MRPVAT adipocytes. Further studies to determine the identity of amidated proteins will give insight into how these enzymes contribute to functions of PVAT and, ultimately, blood pressure.

Perivascular adipose tissue (PVAT), an intriguing layer of fat surrounding blood vessels, regulates vascular tone and mediates vascular dysfunction through mechanisms that are not well understood. Here we show with single nucleus RNA-sequencing of thoracic aortic PVAT from Dahl SS rats that a high-fat (HF) hypertensive diet induces coordinated changes in gene expression across the diverse cell types within PVAT. HF diet produced sex-specific alterations in cell-type proportions and genes related to remodeling of extracellular matrix dynamics and vascular integrity and stiffness, as well as changes in cell-cell communication pathways involved in angiogenesis, vascular remodeling, and mechanotransduction. Gene regulatory network analysis with virtual transcription factor knockout in adipocytes identified specific nuclear receptors that could be targeted for suppression or potential reversal of HF diet-induced changes. Interestingly, generative deep learning models were able to predict cross-cell-type perturbations in gene expression, indicating a hypertensive disease signature that characterizes HF-diet-induced perturbations in PVAT.

Background: Perivascular adipose tissue (PVAT) contains adipocytes and a stromal-vascular fraction with immune cells that modulate the adjacent vasculature. The presence of immune cells in PVAT of vascular beds is poorly understood—are they resident or recruited? We propose a novel resident microbiome present in PVAT, given the immune-rich stromal environment. Hypothesis: We hypothesized the existence of distinct bacterial and viral communities in healthy PVAT compared to non-PVAT adipose tissues. Methods: PVAT samples from thoracic and abdominal aorta, mesenteric resistance arteries, non-PVAT tissues (subscapular brown adipose tissue, retroperitoneal white adipose tissue), and fecal samples were collected one year apart from male Dahl SS rats, split into two cohorts (2023 and 2024, n = 3 each). Whole-genome shotgun sequencing (CosmosID) and 16S rRNA gene analysis assessed microbial relative abundance. Results: PVAT harbored bacterial and viral sequences, and species composition varied significantly between cohorts. Bacterial and viral fecal samples showed lower variability. Conclusions: PVAT microbiome differed dramatically from the fecal microbiome, with temporal influences on bacterial and viral diversity, marking the first such report. Despite inherent limitations, these findings establish the potential of PVAT microbiota in vascular biology and immune modulation, paving the development of microbiome-targeted drugs to address vascular dysfunctions.