Chronic stress induced perivascular adipose tissue impairment of aortic function and the therapeutic effect of exercise

β-Adrenergic Stimulation-Induced PVAT Dysfunction in Male Sex: A Role for 11β-Hydroxysteroid Dehydrogenase-1

Long-term β-adrenoceptor (β-AR) stimulation is a pathological mechanism associated with cardiovascular diseases resulting in endothelial and perivascular adipose tissue (PVAT) dysfunction. In this study, we aimed to identify whether β-adrenergic signaling has a direct effect on PVAT. Thoracic aorta PVAT was obtained from male Wistar rats and cultured ex vivo with the β-AR agonist isoproterenol (Iso; 1 µM) or vehicle for 24 hours. Conditioned culture medium (CCM) from Iso-treated PVAT induced a marked increase in aorta contractile response, induced oxidative stress, and reduced nitric oxide production in PVAT compared to vehicle. In addition, Iso-treated PVAT and PVAT-derived differentiated adipocytes exhibited higher corticosterone release and protein expression of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), an enzyme responsible for de novo synthesis of corticosterone. Macrophages exposed to Iso also exhibited increased corticosterone release in response to β-AR stimulation. Incubation of Iso-treated PVAT and PVAT-derived differentiated adipocytes with β3-AR antagonist restored aorta contractile function modulated by Iso-CCM and normalized 11β-HSD1 protein expression. These results show that β3-AR signaling leads to upregulation of 11β-HSD1 in PVAT, thus increasing corticosterone release and contributing to impair the anticontractile function of this tissue.

Sodium Hydrosulfide Reverts Chronic Stress-Induced Cardiovascular Alterations by Reducing Oxidative Stress

ABSTRACT

Chronic stress induces a group of unrecognized cardiovascular impairments, including elevated hemodynamic variables and vascular dysfunction. Moreover, hydrogen sulfide (H 2 S), a gasotransmitter that regulates the cardiovascular system decreases under chronic stress. Thus, this study assessed the impact of sodium hydrosulfide (NaHS) (H 2 S donor) on chronic restraint stress (CRS)-induced cardiovascular changes. For that purpose, male Wistar rats were restrained for 2 hours a day in a transparent acrylic tube over 8 weeks. Then, body weight, relative adrenal gland weight, serum corticosterone, H 2 S-synthesizing enzymes, endothelial nitric oxide synthetize expression, reactive oxygen species levels, lipid peroxidation, and reduced glutathione-to-oxidized glutathione (GSH 2 :GSSG) ratio were determined in the thoracic aorta. The hemodynamic variables were measured in vivo by the plethysmograph method. The vascular function was evaluated in vitro as vasorelaxant responses induced by carbachol or sodium nitroprusside, and norepinephrine (NE)-mediated vasocontractile responses in the thoracic aorta. CRS increased (1) relative adrenal gland weight; (2) hemodynamic variables; (3) vasoconstrictor responses induced by NE, (4) reactive oxygen species levels, and (5) lipid peroxidation in the thoracic aorta. In addition, CRS decreased (1) body weight; (2) vasorelaxant responses induced by carbachol; (3) GSH content, and (4) GSH 2 :GSSG ratio. Notably, NaHS administration (5.6 mg/kg) restored hemodynamic variables and lipid peroxidation and attenuated the vasoconstrictor responses induced by NE in the thoracic aorta. In addition, NaHS treatment increased relative adrenal gland weight and the GSH 2 :GSSG ratio. Taken together, our results demonstrate that NaHS alleviates CRS-induced hypertension by reducing oxidative stress and restoring vascular function in the thoracic aorta.

Leptin-dependent differential remodeling of visceral and pericardial adipose tissue following chronic exercise and psychosocial stress

Obesity is driven by an imbalance between caloric intake and energy expenditure, causing excessive storage of triglycerides in adipose tissue at different sites around the body. Increased visceral adipose tissue (VAT) is associated with diabetes, while pericardial adipose tissue (PAT) is associated with cardiac pathology. Adipose tissue can expand either through cellular hypertrophy or hyperplasia, with the former correlating with decreased metabolic health in obesity. The aim of this study was to determine how VAT and PAT remodel in response to obesity, stress, and exercise. Here we have used the male obese Zucker rats, which carries two recessive fa alleles that result in the development of hyperphagia with reduced energy expenditure, resulting in morbid obesity and leptin resistance. At 9 weeks of age, a group of lean (Fa/Fa or Fa/fa) Zucker rats (LZR) and obese (fa/fa) Zucker rats (OZR) were treated with unpredictable chronic mild stress or exercise for 8 weeks. To determine the phenotype for PAT and VAT, tissue cellularity and gene expression were analyzed. Finally, leptin signaling was investigated further using cultured 3T3-derived adipocytes. Tissue cellularity was determined following hematoxylin and eosin (H&E) staining, while qPCR was used to examine gene expression. PAT adipocytes were significantly smaller than those from VAT and had a more beige-like appearance in both LZR and OZR. In the OZR group, VAT adipocyte cell size increased significantly compared with LZR, while PAT showed no difference. Exercise and stress resulted in a significant reduction in VAT cellularity in OZR, while PAT showed no change. This suggests that PAT cellularity does not remodel significantly compared with VAT. These data indicate that the extracellular matrix of PAT is able to remodel more readily than in VAT. In the LZR group, exercise increased insulin receptor substrate 1 (IRS1) in PAT but was decreased in the OZR group. In VAT, exercise decreased IRS1 in LZR, while increasing it in OZR. This suggests that in obesity, VAT is more responsive to exercise and subsequently becomes less insulin resistant compared with PAT. Stress increased PPAR-γ expression in the VAT but decreased it in the PAT in the OZR group. This suggests that in obesity, stress increases adipogenesis more significantly in the VAT compared with PAT. To understand the role of leptin signaling in adipose tissue remodeling mechanistically, JAK2 autophosphorylation was inhibited using 5 μM 1,2,3,4,5,6-hexabromocyclohexane (Hex) in cultured 3T3-derived adipocytes. Palmitate treatment was used to induce cellular hypertrophy. Hex blocked adipocyte hypertrophy in response to palmitate treatment but not the increase in lipid droplet size. These data suggest that leptin signaling is necessary for adipocyte cell remodeling, and its absence induces whitening. Taken together, our data suggest that leptin signaling is necessary for adipocyte remodeling in response to obesity, exercise, and psychosocial stress.

Xanthine oxidase mediates chronic stress-induced cerebrovascular dysfunction and cognitive impairment

Xanthine oxidase (XO) mediates vascular function. Chronic stress impairs cerebrovascular function and increases the risk of stroke and cognitive decline. Our study determined the role of XO on stress-induced cerebrovascular dysfunction and cognitive decline. We measured middle cerebral artery (MCA) function, free radical formation, and working memory in 6-month-old C57BL/6 mice who underwent 8 weeks of control conditions or unpredictable chronic mild stress (UCMS) with or without febuxostat (50 mg/L), a XO inhibitor. UCMS mice had an impaired MCA dilation to acetylcholine vs. controls (p < 0.0001), and increased total free radical formation, XOR protein levels, and hydrogen peroxide production in the liver compared to controls. UCMS increased hydrogen peroxide production in the brain and cerebrovasculature compared to controls. Working memory, using the y-maze test, was impaired (p < 0.05) in UCMS mice compared to control mice. However, blocking XO using febuxostat prevented the UCMS-induced impaired MCA response, while free radical production and hydrogen peroxide levels were similar to controls in the liver and brain of UCMS mice treated with febuxostat. Further, UCMS + Feb mice did not have a significant reduction in working memory. These data suggest that the cerebrovascular dysfunction associated with chronic stress may be driven by XO, which leads to a reduction in working memory.

Perivascular adipose tissue: Fine-tuner of vascular redox status and inflammation

Perivascular adipose tissue (PVAT) refers to the aggregate of adipose tissue surrounding the vasculature, exhibiting the phenotypes of white, beige and brown adipocytes. PVAT has emerged as an active modulator of vascular homeostasis and pathogenesis of cardiovascular diseases in addition to its structural role to provide mechanical support to blood vessels. More specifically, PVAT is closely involved in the regulation of reactive oxygen species (ROS) homeostasis and inflammation along the vascular tree, through the tight interaction between PVAT and cellular components of the vascular wall. Furthermore, the phenotype-genotype of PVAT at different regions of vasculature varies corresponding to different cardiovascular risks. During ageing and obesity, the cellular proportions and signaling pathways of PVAT vary in favor of cardiovascular pathogenesis by promoting ROS generation and inflammation. Physiological means and drugs that alter PVAT mass, components and signaling may provide new therapeutic insights in the treatment of cardiovascular diseases. In this review, we aim to provide an updated understanding towards PVAT in the context of redox regulation, and to highlight the therapeutic potential of targeting PVAT against cardiovascular complications.

Indirect Antioxidant Effects of the Nitrite Anion: Focus on Xanthine Oxidase

One electron reduction of nitrite (NO₂ ^-) has been determined to be a significant, noncanonical source of nitric oxide (NO) with molybdopterin enzymes being identified as critical to this process. Of the molybdopterin enzymes identified as NO₂ ^- reductases, xanthine oxidoreductase (XOR) is the most extensively studied. Paradoxically, XOR generates oxidants and thus can contribute to oxidative stress under inflammatory conditions when the oxidase form (XO) of XOR is abundant. However, under similar inflammatory conditions XO has been associated with NO generation, especially when NO₂ ^- levels are elevated which begs the question: if reaction of nitrite with XO consumes electrons, then does it subsequently reduce oxidant generation? To address this question, electron paramagnetic resonance (EPR) was used, under controlled O₂ tensions, to assess superoxide (O₂ ^•-) generation by endothelial-bound XO plus xanthine and the resultant impact of introducing NO₂ ^-. Nitrite diminished XO-derived O₂ ^•- under hypoxia (1% O₂) whereas at 21% O₂, it had no impact. To confirm these results and discount contributions from the reaction of NO with O₂ ^•-, molecular O₂ consumption was assessed. The presence of NO₂ ^- decreased the rate of XO/xanthine-dependent O₂ consumption in a concentration-dependent manner with greater impact under hypoxic conditions (1% O₂) compared to 21% O₂. In a more biologic setting, NO₂ ^- also diminished XO-dependent H₂O₂ formation in murine liver homogenates supplemented with xanthine. Interestingly, nitrate (NO₃ ^-) did not alter XO-dependent O₂ consumption at either 21% or 1% O₂; yet it did slightly impact nitrite-mediated effects when present at 2:1 ratio vs. NO₂ ^-. When combined, these data: 1) show a significant indirect antioxidant function for NO₂ ^- by decreasing oxidant generation from XO, 2) demonstrate that both XO-derived H₂O₂ and O₂ ^•- production are diminished by the presence of NO₂ ^- and 3) incentivize further exploration of the difference between XO reaction with NO₂ ^- vs. NO₃ ^-.

Aerobic Exercise Prevents Arterial Stiffness and Attenuates Hyperexcitation of Sympathetic Nerves in Perivascular Adipose Tissue of Mice after Transverse Aortic Constriction

We aimed to investigate the efficacy of exercise on preventing arterial stiffness and the potential role of sympathetic nerves within perivascular adipose tissue (PVAT) in pressure-overload-induced heart failure (HF) mice. Eight-week-old male mice were subjected to sham operation (SHAM), transverse aortic constriction-sedentary (TAC-SE), and transverse aortic constriction-exercise (TAC-EX) groups. Six weeks of aerobic exercise training was performed using a treadmill. Arterial stiffness was determined by measuring the elastic modulus. The elastic and collagen fibers of the aorta and sympathetic nerve distribution in PVAT were observed. Circulating noradrenaline (NE), expressions of β3-adrenergic receptor (β3-AR), and adiponectin in PVAT were quantified. During the recovery of cardiac function by aerobic exercise, thoracic aortic collagen elastic modulus (CEM) and collagen fibers were significantly decreased (p < 0.05, TAC-SE vs. TAC-EX), and elastin elastic modulus (EEM) was significantly increased (p < 0.05, TAC-SE vs. TAC-EX). Circulating NE and sympathetic nerve distribution in PVAT were significantly decreased (p < 0.05, TAC-SE vs. TAC-EX). The expression of β3-AR was significantly reduced (p < 0.05, TAC-SE vs. TAC-EX), and adiponectin was significantly increased (p < 0.05, TAC-SE vs. TAC-EX) in PVAT. Regular aerobic exercise can effectively prevent arterial stiffness and extracellular matrix (ECM) remodeling in the developmental course of HF, during which sympathetic innervation and adiponectin within PVAT might be strongly implicated.

Nano-titanium dioxide inhalation exposure during gestation drives redox dysregulation and vascular dysfunction across generations

BACKGROUND

Pregnancy is associated with many rapid biological adaptations that support healthy development of the growing fetus. One of which is critical to fetal health and development is the coordination between maternal liver derived substrates and vascular delivery. This crucial adaptation can be potentially derailed by inhalation of toxicants. Engineered nanomaterials (ENM) are commonly used in household and industrial products as well as in medicinal applications. As such, the potential risk of exposure remains a concern, especially during pregnancy. We have previously reported that ENM inhalation leads to upregulation in the production of oxidative species. Therefore, we aimed to determine if F0 dam maternal nano-TiO₂ inhalation exposure (exclusively) resulted in altered H₂O₂ production capacity and changes in downstream redox pathways in the F0 dams and subsequent F1 pups. Additionally, we investigated whether this persisted into adulthood within the F1 generation and how this impacted F1 gestational outcomes and F2 fetal health and development. We hypothesized that maternal nano-TiO₂ inhalation exposure during gestation in the F0 dams would result in upregulated H₂O₂ production in the F0 dams as well as her F1 offspring. Additionally, this toxicological insult would result in gestational vascular dysfunction in the F1 dams yielding smaller F2 generation pups.

RESULTS

Our results indicate upregulation of hepatic H₂O₂ production capacity in F0 dams, F1 offspring at 8 weeks and F1 females at gestational day 20. H₂O₂ production capacity was accompanied by a twofold increase in phosphorylation of the redox sensitive transcription factor NF-κB. In cell culture, naïve hepatocytes exposed to F1-nano-TiO₂ plasma increased H₂O₂ production. Overnight exposure of these hepatocytes to F1 plasma increased H₂O₂ production capacity in a partially NF-κB dependent manner. Pregnant F1- nano-TiO₂ females exhibited estrogen disruption (12.12 ± 3.1 pg/ml vs. 29.81 ± 8.8 pg/ml sham-control) and vascular dysfunction similar to their directly exposed mothers. F1-nano-TiO₂ uterine artery H₂O₂ production capacity was also elevated twofold. Dysfunctional gestational outcomes in the F1-nano-TiO₂ dams resulted in smaller F1 (10.22 ± 0.6 pups vs. sham-controls 12.71 ± 0.96 pups) and F2 pups (4.93 ± 0.47 g vs. 5.78 ± 0.09 g sham-control pups), and fewer F1 male pups (4.38 ± 0.3 pups vs. 6.83 ± 0.84 sham-control pups).

CONCLUSION

In conclusion, this manuscript provides critical evidence of redox dysregulation across generations following maternal ENM inhalation. Furthermore, dysfunctional gestational outcomes are observed in the F1-nano-TiO₂ generation and impact the development of F2 offspring. In total, this data provides strong initial evidence that maternal ENM exposure has robust biological impacts that persists in at least two generations.

Recent Progress of Chronic Stress in the Development of Atherosclerosis

With the development of the times, cardiovascular diseases have become the biggest cause of death in the global aging society, causing a serious social burden. Atherosclerosis is a chronic inflammatory disease, which can occur in large and medium-sized blood vessels in the whole body. It takes atherosclerotic plaque as the typical pathological change and endothelial injury as the core pathophysiological mechanism. It is the pathological basis of coronary heart disease, peripheral artery disease, cerebrovascular disease, and other diseases. Recent studies have shown that chronic stress plays an important role in the occurrence and development of atherosclerosis, endothelial injury, lipid metabolism, and chronic inflammation. This process involves a large number of molecular targets. It is usually the cause of atherosclerotic cardiovascular and cerebrovascular diseases. If chronic stress factors exist for a long time, patients have genetic susceptibility, and the combination of environmental factors triggers the pathogenesis, which may eventually lead to complete blockage of the blood vessels, unstable rupture of plaques, and serious adverse cardiovascular events. This paper reviews the role of chronic stress in the occurrence and development of atherosclerosis, focusing on the pathophysiological mechanism.