Estrogen deprivation does not affect vascular heat shock response in female rats: a comparison with oxidative stress markers

Effects of Guizhi and Erxian Decoction on menopausal hot flashes: insights from the gut microbiome and metabolic profiles

AIMS

To examine the influence of GED on the gut microbiota and metabolites using a bilateral ovariectomized (OVX) rat model. We tried to elucidate the underlying mechanisms of GED in the treatment of menopausal hot flashes.

METHODS AND RESULTS

16S rRNA sequencing, metabonomics, molecular biological analysis, and fecal microbiota transplantation (FMT) were conducted to elucidate the mechanisms by which GED regulates the gut microbiota. GED significantly reduced OVX-induced hot flashes and improved disturbances in the gut microbiota metabolites. Moreover, FMT validated that the gut microbiota can trigger hot flashes, while GED can alleviate hot flash symptoms by modulating the composition of the gut microbiota. Specifically, GED upregulated the abundance of Blautia, thereby increasing l(+)-ornithine levels for the treatment of menopausal hot flashes. Additionally, GED affected endothelial nitric oxide synthase and heat shock protein 70 (HSP70) levels in the hypothalamic preoptic area by changing the gut microbiota composition.

CONCLUSIONS

Our study illuminated the underlying mechanisms by which GED attenuated the hot flashes through modulation of the gut microbiota and explored the regulatory role of the gut microbiota on HSP70 expression in the preoptic anterior hypothalamus, thereby establishing a foundation for further exploration of the role of the gut-brain axis in hot flashes.

Increased eHSP70-to-iHSP70 ratio in prediabetic and diabetic postmenopausal women: a biomarker of cardiometabolic risk

Decreased estrogen levels in menopause are associated with anthropometric, metabolic, and inflammatory impairments, predisposing women to cardiometabolic risk factors such as diabetes. Menopause and type two diabetes (DM2) are marked by altered heat shock response (HSR), shown by decreased expression of the 70-kDa heat shock protein in the intracellular milieu (iHSP70). While iHSP70 plays an anti-inflammatory role, extracellular HSP70 (eHSP70) may mediate pro-inflammatory pathways and has been associated with insulin resistance in DM2. Considering the roles of these proteins according to localization, the eHSP70-to-iHSP70 ratio (H-index) has been proposed as a biomarker for HSR. We, therefore, evaluated whether this biomarker is associated with glycemic and inflammatory status in postmenopausal women. In this transversal study, 36 postmenopausal women were grouped according to fasting glycemia status as either the control group (normoglycemic, ≤ 99 mg/dL) or DM2 (prediabetic and diabetic, glycemia ≥ 100 mg/dL). DM2 group showed higher triglyceride/glucose (TyG) index and plasma atherogenic index (PAI), both of which are indicators of cardiometabolic risk. In addition, we found that the eHSP70-to-iHSP70 ratio (plasma/peripheral blood mononuclear cells-PBMC ratio) was higher in the DM2 group, compared with the control group. Furthermore, blood leukocyte and glycemia levels were positively correlated with the eHSP70-to-iHSP70 ratio in women that presented H-index values above 1.0 (a.u.). Taken together, our results highlight the eHSP70-to-iHSP70 ratio as a biomarker of altered HSR in DM2 postmenopausal women.

Ovariectomy reduces the cardiac cytoprotection in rats exposed to particulate air pollutant

Fine particulate matter (PM_2.5) has been considered a risk factor for cardiovascular diseases by inducing an oxidative and inflammatory phenotype. Besides, the reduction of 17β-estradiol (E2) levels during menopause is a natural risk for cardiovascular outcomes. During the E2 downfall, there is a high requirement of the 70-kDa heat shock proteins (HSP70), which present essential antioxidant, anti-inflammatory, and anti-senescence roles. We investigated if the ovariectomy, an animal model for menopause, could induce additional effects in cardiac health by impairing oxidative and heat shock response parameters of female rats chronically exposed to residual oil fly ash (ROFA; an inorganic fraction of PM_2.5). Thus, ROFA was obtained from São Paulo (Brazil) and solubilized it in saline. Further, female Wistar rats were exposed to 50 μL of saline (control group) or ROFA solution (250 μg) (polluted) by intranasal instillation, 5 days/week, 12 weeks. At the 12th week, animals were subdivided into four groups (n = 6 p/group): control, OVX, polluted, and polluted + OVX. Control and polluted were submitted to false surgery, while OVX and polluted + OVX were ovariectomized. ROFA or saline exposure continued for 12 weeks. Ovariectomy reduced the cardiac catalase activity and iHSP70 expression in female rats exposed to ROFA. Neither plasma eHSP72 levels nor H-index (eHSP72 to cardiac iHSP70 ratio) was affected. In conclusion, ovariectomy reduces the cardiac cytoprotection and antioxidant defense, and enhances the susceptibility to premature cellular senescence in rats exposed to ROFA.

Impaired HSP70 Expression in the Aorta of Female Rats: A Novel Insight Into Sex-Specific Differences in Vascular Function

Heat-shock protein 70 (HSP70) contributes to cellular calcium (Ca2+) handling mechanisms during receptor-mediated vascular contraction. Interestingly, previous studies have independently reported sex-related differences in HSP70 expression and Ca2+ dynamics. Still, it is unknown if sex, as a variable, plays a role in the impact that HSP70 has upon vascular contraction. To narrow this gap, we investigated if differences exist in the expression levels of HSP70 in the aorta, and if targeting this protein contributes to sex disparity in vascular responses. We report that, compared with male animals, female rats present a reduction in the basal levels of HSP70. More compelling, we found that the blockade of HSP70 has a greater impact on phenylephrine-induced phasic and tonic vascular contraction in female animals. In fact, it seems that the inhibition of HSP70 significantly affects vascular Ca2+ handling mechanisms in females, which could be associated with the fact that these animals have impaired HSP70 expression. Corroborating this idea, we uncovered that the higher sensitivity of female rats to HSP70 inhibition does not involve an increase in NO-dependent vasodilation nor a decrease in vascular oxidative stress. In summary, our findings reveal a novel mechanism associated with sex-specific differences in vascular responses to α-1 adrenergic stimulation, which might contribute to unraveling the network of intertwined pathways conferring female protection to (cardio)vascular diseases.

Oxidative and Cellular Stress Markers in Postmenopause Women with Diabetes: The Impact of Years of Menopause

Women live approximately one-third of their lives in postmenopause. Among postmenopausal women, type 2 diabetes mellitus (DM2) is one of the most prevalent chronic diseases. These conditions promote alterations in the oxidative, metabolic, and immune-inflammatory profiles marked by higher extracellular 72 kDa-heat shock protein (eHSP72). Here, we investigated whether the time of menopause is associated with oxidative cellular stress marker levels in postmenopausal women with DM2. Sixty-four women were recruited (56.7 ± 12.6 years old) in the pre- (n = 22) and postmenopause (n = 42) period, with (n = 19) or without DM2 (n = 45), and a fasting blood collection was made for the evaluation of metabolic, oxidative, and inflammatory markers. We found that menopause and DM2 influenced metabolic and oxidative parameters and presented synergistic effects on the plasma lipoperoxidation levels. Also, postmenopausal women had the highest eHSP72 concentration levels associated with the years in postmenopause. We conclude that the time of menopause impacts the markers of cellular stress and increases the risk of oxidative stress, mainly when it is associated with DM2.

Ovariectomy enhances female rats' susceptibility to metabolic, oxidative, and heat shock response effects induced by a high-fat diet and fine particulate matter

Obesity and exposure to fine particulate matter (air pollutant PM_2.5) are important risk factors for metabolic and cardiovascular diseases. They are also related to early menopause. The reduction of 17β-estradiol (E2) levels during female climacteric, marked by menopause, is of significant concern because of its imminent influence on metabolism, redox and inflammatory status. This complex homeostasis-threatening scenario may induce a heat shock response (HSR) in cells, enhancing the expression of the 70 kDa heat shock protein (HSP70). A failure in this mechanism could predispose women to cardiovascular diseases. In this study, we evaluated if the climacteric could represent an additional risk among obese rats exposed to PM_2.5 by worsening lipid, oxidative, and inflammatory parameters and HSP70 in cardiac tissue. We induced obesity in female Wistar rats using a high-fat diet (HFD) (58.3% as fats) and exposed them to 50 μL of saline 0.9% (control, n = 15) or 250 μg residual oil fly ash (ROFA, the inorganic portion of PM_2.5) (polluted, n = 15) by intranasal instillation, 5 days/w for 12 weeks. At the 12th week, we subdivided these animals into four groups: control (n = 6), OVX (n = 9), polluted (n = 6) and polluted + OVX (n = 9). OVX and polluted + OVX were submitted to a bilateral ovariectomy (OVX), a surgical model for menopause, while control and polluted received a false surgery (sham). ROFA exposure and HFD consumption were continued for 12 additional weeks, after which the animals were euthanized. ROFA enhanced the susceptibility to ovariectomy-induced dyslipidemia, while ovariectomy predisposed female rats to the ROFA-induced decrease of cardiac iHSP70 expression. Ovariectomy also decreased the IL-6 levels and IL-6/IL-10 in obese animals, reinforcing a metabolic impairment and a failure to respond to unfavorable conditions. Our results support the hypothesis that obese ovariectomized animals are predisposed to a metabolic worsening under polluted conditions and are at higher risk of cardiovascular diseases.

Chronic heat treatment positively impacts metabolic profile of ovariectomized rats: association with heat shock response pathways

Low estrogen levels may predispose women to increased bodyweight and dyslipidemia. Previous studies from our laboratory suggest an involvement of depressed heat shock response (HSR) in this scenario because estrogen potently stimulates HSR. As heat treatment induces the expression of the anti-inflammatory heat shock proteins of the 70-kDa family (HSP70) and its accompanying HSR, we aimed to investigate whether chronic heat treatment promotes beneficial effects on biometric, lipid profile, oxidative stress, and HSR in ovariectomized rats. Wistar adult female rats (n = 32) were divided into four groups: control (C, n = 7), ovariectomized (OVX, n = 9), heat-treated (HT, n = 9), and heat-treated ovariectomized rats (OVX+HT, n = 7). HT and OVX+HT rats were anesthetized and submitted to heat treatment (once a week for 12 weeks) in a water bath (41 °C) to increase rats' rectal temperature up to 41 °C for 15 min, while C and OVX animals were submitted to a 36 °C water bath. HT attenuated the weight gain induced by OVX and increased HDL cholesterol and triglyceride serum levels. Also, OVX rats showed increased total cholesterol and LDL cholesterol levels that were not influenced by HT. Interestingly, it was found that an overall trend for HT to decrease tissue catalase and superoxide dismutase antioxidant activities was paralleled by a decrease in malondialdehyde levels (indicative of lower lipoperoxidation), especially in the skeletal muscle. Surprisingly, OVX was not able to depress intracellular HSP70 expression in the skeletal muscle, as expected, and this remained unchanged with HT. However, chronic HT did enhance intracellular HSP70 contents in white adipose tissue of OVX animals. As both glucose and insulin tolerance tests were not affected by OVX, which was not modified by HT, we suppose that estrogen absence alone is not sufficient to determine a state of insulin resistance associated with low intramuscular HSP70 content.

Heat shock response to exercise in pancreatic islets of obese mice

Chronic obesity imposes an organismal state of low-grade inflammation because the physiological resolution of inflammation is progressively repressed giving rise to cellular senescence and its accompanying Senescence-Associated Secretory Phenotype (SASP), which avoids apoptosis but perpetuates the relay of inflammatory signals from adipose tissue toward the rest of the body. Conversely, resolution of inflammation depends on the integrity of heat shock response (HSR) pathway that leads to the expression of cytoprotective and anti-inflammatory protein chaperones of the 70 kDa family (HSP70). However, chronic exposure to the aforementioned injuring factors leads to SASP, which, in turn, suppresses the HSR. A main metabolic tissue severely jeopardized by obesity-related dysfunctions is the endocrine pancreas, particularly β-cells of the islets of Langerhans. Because exercise is a powerful inducer of HSR and predicted to alleviate negative health outcomes of obesity, we sought whether obesity influence HSP70 expression in pancreatic islets and other metabolic tissues (adipose tissue and skeletal muscle) of adult B6.129SF2/J mice fed on a high-fat diet (HFD) for 13 weeks since the weaning and whether acute exercise as well as moderate-intensity exercise training (8 weeks) could interfere with this scenario. We showed that acute exercise of moderate intensity protects pancreatic islets against cytokine-induced cell death. In addition, acute exercise challenge time-dependently increased islet HSP70 that peaked at 12 h post-exercise in both trained and untrained mice fed on a control diet, suggesting an adequate HSR to exercise training. Unexpectedly, however, neither exercise training nor acute exercise challenges were able to increase islet HSP70 contents in trained mice submitted to HFD, but only in untrained HFD animals. In parallel, HFD disrupted glycemic status which is accompanied by loss of muscular mass resembling sarcopenic obesity that could not be rescued by exercise training. These results suggest that exercise influences HSR in pancreatic islets but obesity undermines islet, muscle and adipose tissue HSR, which is associated with metabolic abnormalities observed in such tissues.

Ovariectomy predisposes female rats to fine particulate matter exposure's effects by altering metabolic, oxidative, pro-inflammatory, and heat-shock protein levels

The reduction of estrogen levels, as a result of menopause, is associated with the development of metabolic diseases caused by alterations in oxidative stress (OS), inflammatory biomarkers, and 70-kDa heat-shock protein (HSP70) expression. Additionally, exposure to fine particulate matter air pollution modifies liver OS levels and predisposes organisms to metabolic diseases, such as type 2 diabetes (T2DM). We investigated whether ovariectomy affects hepatic tissue and alters glucose metabolism in female rats exposed to particulate air pollution. First, 24 female Wistar rats received an intranasal instillation of saline or particles suspended in saline 5 times per week for 12 weeks. The animals then received either bilateral ovariectomy (OVX) or false surgery (sham) and continued to receive saline or particles for 12 additional weeks, comprising four groups: CTRL, Polluted, OVX, and Polluted+OVX. Ovariectomy increased body weight and adiposity and promoted edema in hepatic tissue, hypercholesterolemia, glucose intolerance, and a pro-inflammatory profile (reduced IL-10 levels and increased IL-6/IL-10 ratio levels), independent of particle exposure. The Polluted+OVX group showed an increase in neutrophils and neutrophil/lymphocyte ratios, decreased antioxidant defense (SOD activity), and increased liver iHSP70 levels. In conclusion, alterations in the reproductive system predispose female organisms to particulate matter air pollution effects by affecting metabolic, oxidative, pro-inflammatory, and heat-shock protein expression.

Subacute exposure to residual oil fly ash (ROFA) increases eHSP70 content and extracellular-to-intracellular HSP70 ratio: a relation with oxidative stress markers

The purpose of this study was to evaluate whether exposure to particles induces an imbalance in 70-kDa heat shock proteins (HSP70). Since intracellularly (iHSP70) it has anti-inflammatory roles whereas extracellularly (eHSP70) it has pro-inflammatory roles, we evaluate the effect of residual oil fly ash (ROFA) exposure on eHSP70-to-iHSP70 ratio (H index), a biomarker of inflammatory status that is related to oxidative stress in plasma and lymphoid tissue. Wistar rats that received ROFA suspension for three consecutive days (750 μg) showed an increase in plasma eHSP70 levels (mainly the 72-kDa inducible form). Also, ROFA promoted alterations on plasma oxidative stress (increased protein carbonyl groups and superoxide dismutase activity, and decrease sulfhydryl groups). There was an increase in H index of the plasma/thymus with no changes in circulating leukocyte level, iHSP70, or oxidative stress markers in lymphoid tissues. Our results support the hypothesis that eHSP70 content and H index represent inflammatory and oxidative biomarkers.

17-β Estradiol regulates proglucagon-derived peptide secretion in mouse and human α- and L cells

Clinical and experimental data indicate a beneficial effect of estrogens on energy and glucose homeostasis associated with improved insulin sensitivity and positive effects on insulin secretion. The aim of the study was to investigate the impact of estrogens on proglucagon-producing cells, pancreatic α cells, and enteroendocrine L cells. The consequences of sexual hormone deprivation were evaluated in ovariectomized mice (ovx). Ovx mice exhibited impaired glucose tolerance during oral glucose tolerance tests (OGTT), which was associated with decreased GLP-1 intestinal and pancreatic secretion and content, an effect that was reversed by estradiol (E2) treatment. Indeed, E2 increased oral glucose-induced GLP-1 secretion in vivo and GLP-1 secretion from primary culture of mouse and human α cells through the activation of all 3 estrogen receptors (ERs), whereas E2-induced GLP-1 secretion from mouse and human intestinal explants occurred only by ERβ activation. Underlying the implication of ERβ, its selective agonist WAY20070 was able to restore glucose tolerance in ovx mice at least partly through plasma GLP-1 increase. We conclude that E2 directly controls both α- and L cells to increase GLP-1 secretion, in addition to its effects on insulin and glucagon secretion, highlighting the potential beneficial role of the estrogenic pathway and, more particularly, of ERβ agonists to prevent type 2 diabetes.

Nitric oxide-heat shock protein axis in menopausal hot flushes: neglected metabolic issues of chronic inflammatory diseases associated with deranged heat shock response

BACKGROUND

Although some unequivocal underlying mechanisms of menopausal hot flushes have been demonstrated in animal models, the paucity of similar approaches in humans impedes further mechanistic outcomes. Human studies might show some as yet unexpected physiological mechanisms of metabolic adaptation that permeate the phase of decreased oestrogen levels in both symptomatic and asymptomatic women. This is particularly relevant because both the severity and time span of hot flushes are associated with increased risk of chronic inflammatory disease. On the other hand, oestrogen induces the expression of heat shock proteins of the 70 kDa family (HSP70), which are anti-inflammatory and cytoprotective protein chaperones, whose expression is modulated by different types of physiologically stressful situations, including heat stress and exercise. Therefore, lower HSP70 expression secondary to oestrogen deficiency increases cardiovascular risk and predisposes the patient to senescence-associated secretory phenotype (SASP) that culminates in chronic inflammatory diseases, such as obesities, type 2 diabetes, neuromuscular and neurodegenerative diseases.

OBJECTIVE AND RATIONALE

This review focuses on HSP70 and its accompanying heat shock response (HSR), which is an anti-inflammatory and antisenescent pathway whose intracellular triggering is also oestrogen-dependent via nitric oxide (NO) production. The main goal of the manuscript was to show that the vasomotor symptoms that accompany hot flushes may be a disguised clue for important neuroendocrine alterations linking oestrogen deficiency to the anti-inflammatory HSR.

SEARCH METHODS

Results from our own group and recent evidence on hypothalamic control of central temperature guided a search on PubMed and Google Scholar websites.

OUTCOMES

Oestrogen elicits rapid production of the vasodilatory gas NO, a powerful activator of HSP70 expression. Whence, part of the protective effects of oestrogen over cardiovascular and neuroendocrine systems is tied to its capacity of inducing the NO-elicited HSR. The hypothalamic areas involved in thermoregulation (infundibular nucleus in humans and arcuate nucleus in other mammals) and whose neurons are known to have their function altered after long-term oestrogen ablation, particularly kisspeptin-neurokinin B-dynorphin neurons, (KNDy) are the same that drive neuroprotective expression of HSP70 and, in many cases, this response is via NO even in the absence of oestrogen. From thence, it is not illogical that hot flushes might be related to an evolutionary adaptation to re-equip the NO-HSP70 axis during the downfall of circulating oestrogen.

WIDER IMPLICATIONS

Understanding of HSR could shed light on yet uncovered mechanisms of menopause-associated diseases as well as on possible manipulation of HSR in menopausal women through physiological, pharmacological, nutraceutical and prebiotic interventions. Moreover, decreased HSR indices (that can be clinically determined with ease) in perimenopause could be of prognostic value in predicting the moment and appropriateness of starting a HRT.