PI3K/Akt-independent NOS/HO activation accounts for the facilitatory effect of nicotine on acetylcholine renal vasodilations: modulation by ovarian hormones

Estrogenic actions of alkaloids: Structural characteristics and molecular mechanisms

This comprehensive review of estrogenic alkaloids reveals that although the number is small, they exhibit a wide range of structures, biosynthesis pathways, mechanisms of action, and applications. Estrogenic alkaloids belong to different classes, different biosynthetic pathways, different estrogenic actions (estrogenic/synergistic, anti-estrogenic/antagonistic, biphasic, and acting as a selective estrogen receptor modulator or SERM), different receptor-initiated signaling pathways, different ways of modulations of estrogen action, and different applications. The future applications of estrogenic alkaloids, such as those for diagnostics, drug development, and therapeutics, are considered with the help of new databases containing comprehensive descriptions of their relationships and more elaborate artificial intelligence-based prediction technologies. Structure-activity studies reveal the significance of the nitrogen atom for their structural and functional diversity, which may help support their broader applications. Based on the summary of previous reports, estrogenic alkaloids have significant potential for future applications.

Preeclamptic programming unevenly perturbs inflammatory and renal vasodilatory outcomes of endotoxemia in rat offspring: modulation by losartan and pioglitazone

Introduction: Preeclampsia (PE) enhances the vulnerability of adult offspring to serious illnesses. The current study investigated whether preeclamptic fetal programming impacts hemodynamic and renal vasodilatory disturbances in endotoxic adult offspring and whether these interactions are influenced by antenatal therapy with pioglitazone and/or losartan. Methods: PE was induced by oral administration of L-NAME (50 mg/kg/day) for the last 7 days of pregnancy. Adult offspring was treated with lipopolysaccharides (LPS, 5 mg/kg) followed 4-h later by hemodynamic and renovascular studies. Results: Tail-cuff measurements showed that LPS decreased systolic blood pressure (SBP) in male, but not female, offspring of PE dams. Moreover, PE or LPS reduced vasodilations elicited by acetylcholine (ACh, 0.01-7.29 nmol) or N-ethylcarboxamidoadenosine (NECA, 1.6-100 nmol) in perfused kidneys of male rats only. The latter effects disappeared in LPS/PE preparations, suggesting a postconditioning action for LPS against renal manifestation of PE. Likewise, elevations caused by LPS in serum creatinine and inflammatory cytokines (TNFα and IL-1β) as well as in renal protein expression of monocyte chemoattractant protein-1 (MCP-1) and AT1 receptors were attenuated by the dual PE/LPS challenge. Gestational pioglitazone or losartan reversed the attenuated ACh/NECA vasodilations in male rats but failed to modify LPS hypotension or inflammation. The combined gestational pioglitazone/losartan therapy improved ACh/NECA vasodilations and eliminated the rises in serum IL-1β and renal MCP-1 and AT1 receptor expressions. Conclusion: Preeclamptic fetal programming of endotoxic hemodynamic and renal manifestations in adult offspring depends on animal sex and specific biological activity and are reprogrammed by antenatal pioglitazone/losartan therapy.

The renin-angiotensin system modulates endotoxic postconditioning of exacerbated renal vasoconstriction in preeclamptic offspring

We recently reported exacerbated endotoxic signs of neuroinflammation and autonomic defects in offspring of preeclamptic (PE) dams. Here, we investigated whether PE programming similarly modifies hemodynamic and renal vasoconstrictor responsiveness to endotoxemia in PE offspring and whether this interaction is modulated by gestational angiotensin 1-7 (Ang1-7). Preeclampsia was induced by gestational treatment with L-NAME. Adult offspring was challenged with lipopolysaccharides (LPS, 5 mg/kg) and systolic blood pressure (SBP) and renal vasoconstrictions were assessed 4 h later. Male, but not female, offspring of PE rats exhibited SBP elevations that were blunted by LPS. Renal vasoconstrictions induced by angiotensin II (Ang II), but not phenylephrine, were intensified in perfused kidneys of either sex. LPS blunted the heightened Ang II responses in male, but not female, kidneys. While renal expressions of AT1-receptors and angiotensin converting enzyme (ACE) were increased in PE offspring of both sexes, ACE2 was upregulated in female offspring only. These molecular effects were diminished by LPS in male offspring. Gestational Ang1-7 caused sex-unrelated attenuation of phenylephrine vasoconstrictions and preferentially downregulated Ang II responses and AT1-receptor and nuclear factor-kB (NFkB) expressions in females. Together, endotoxemia and Ang1-7 offset in sexually-related manners imbalances in renal vasoconstriction and AT1/ACE/ACE2 signaling in PE offspring.

Modulation of preeclampsia by the cholinergic anti-inflammatory pathway: Therapeutic perspectives

The cholinergic anti-inflammatory pathway (CAP) is vital for the orchestration of the immune and inflammatory responses under normal and challenged conditions. Over the past two decades, peripheral and central circuits of CAP have been shown to be critically involved in dampening the inflammatory reaction in a wide array of inflammatory disorders. Additionally, emerging evidence supports a key role for CAP in the regulation of the female reproductive system during gestation as well as in the advent of serious pregnancy-related inflammatory insults such as preeclampsia (PE). Within this framework, the modulatory action of CAP encompasses the perinatal maternal and fetal adverse consequences that surface due to antenatal PE programming. Albeit, a considerable gap still exists in our knowledge of the precise cellular and molecular underpinnings of PE/CAP interaction, which hampered global efforts in safeguarding effective preventive or therapeutic measures against PE complications. Here, we summarize reports in the literature regarding the roles of peripheral and reflex cholinergic neuroinflammatory pathways of nicotinic acetylcholine receptors (nAChRs) in reprogramming PE complications in mothers and their progenies. The possible contributions of α7-nAChRs, cholinesterases, immune cells, adhesion molecules, angiogenesis, and endothelial dysfunction to the interaction have also been reviewed.

Nicotine Improves Survivability, Hypotension, and Impaired Adenosinergic Renal Vasodilations in Endotoxic Rats: Role of α7-nAChRs/HO-1 Pathway

The nicotinic/cholinergic antiinflammatory pathway protects against acute kidney injury and other end-organ damages induced by endotoxemia. In this study, we tested the hypothesis that functional α7-nAChRs/heme oxygenase-1 (HO-1) pathway is imperative for the nicotine counteraction of hemodynamic and renovascular dysfunction caused by acute endotoxemia in rats. Renal vasodilations were induced by cumulative bolus injections of acetylcholine (ACh, 0.01 nmol-7.29 nmol) or ethylcarboxamidoadenosine (NECA, adenosine receptor agonist, 1.6 nmol-100 nmol) in isolated phenylephrine-preconstricted perfused kidneys. The data showed that 6-h treatment with lipopolysaccharide (LPS, 5 mg/kg i.p.) decreased systolic blood pressure and renal vasodilations caused by NECA but not Ach. The endotoxic insult also increased the mortality rate and elevated serum urea and creatinine. These LPS effects were sex-unrelated, except hypotension, and enhanced mortality which were more evident in male rodents, and abrogated after co-administration of nicotine (0.5, 1 mg/kg and 2 mg/kg) in a dose-dependent fashion. The advantageous effects of nicotine on NECA vasodilations, survivability, and kidney biomarkers in endotoxic male rats disappeared upon concurrent exposure to methyllycaconitine citrate (α7-nAChR blocker) or zinc protoporphyrin (HO-1 inhibitor) and were reproduced after treatment with bilirubin, but not hemin (HO-1 inducer) or tricarbonyldichlororuthenium (II) dimer (carbon monoxide-releasing molecule). Together, current biochemical and pharmacological evidence suggests key roles for α7-nAChRs and the bilirubin byproduct of the HO-1 signaling in the nicotine counteraction of renal dysfunction and reduced adenosinergic renal vasodilator capacity in endotoxic rats.

Ovariectomy provokes inflammatory and cardiovascular effects of endotoxemia in rats: Dissimilar benefits of hormonal supplements

The female gender is protected against immunological complications of endotoxemia. Here we investigated whether gonadal hormone depletion by ovariectomy (OVX) uncovers inflammatory and cardiovascular effects of endotoxemia and whether these effects are reversed by hormone replacement therapies. Changes in inflammatory cytokines, blood pressure (BP), left ventricular (LV) function, and cardiac autonomic activity caused by lipopolysaccharide (LPS) in conscious female rats with different hormonal states were determined. In contrast to no effects in sham-operated females, treatment of OVX rats with LPS (i) decreased BP, (ii) increased spectral low-frequency/high-frequency ratio of HRV, denoting enhanced cardiac sympathetic dominance, (iii) attenuated reflex tachycardic responses to sodium nitroprusside, and (iv) increased systolic contractility (dP/dt_max). The developed hypotension was (i) fully eliminated in estrogen (E₂)-pretreated OVX rats, (ii) partially counteracted after selective activation of estrogen receptor-α (PPT) or β (DPN). All estrogenic compounds abrogated LPS enhancement of cardiac sympathetic drive. However, PPT was more successful than E2 or DPN in compromising LPS depression in baroreflex activity and elevation in dP/dt_max. Molecular studies showed that PPT was most effective in attenuating the upregulated myocardial expressions of NF-κB and iNOS in endotoxic OVX rats. Myocardial expression of the defensive HSP70 was comparably increased by all estrogenic products. Except for improved cardiac spectral activity, none of these functional or molecular entities was affected by medroxyprogesterone acetate (MPA). Overall, our data suggest diverse therapeutic advantages for gonadal hormones in the worsened endotoxic complications in rats with surgical menopause, with probably more favorable role for ERα agonism within this context.

Time and sex dependency of hemodynamic, renal, and survivability effects of endotoxemia in rats

Widely different exposure times to endotoxic insults have been employed in reported studies. The current experimental study systematically evaluated the time-course and sex influences of endotoxic insult on survivability and cardiovascular and renal functions. Rats received i.p. lipopolysaccharide (LPS, 5 mg/kg) once or twice (over 2 successive days). Systolic blood pressure (SBP), biomarkers of renal function and inflammation, and vasodilator responsiveness of isolated perfused kidneys to acetylcholine (ACh) or N-ethylcarboxamidoadenosine (NECA) were evaluated 6 hr after first LPS injection or 1, 2, or 6 days later. A single 6-hr LPS challenge caused (i) sex-unrelated elevations in serum urea and creatinine and reductions in NECA, but not ACh, vasodilations, (ii) more increases in renal NF-κB/iNOS expressions in male than in female rats, and (iii) hypotension and tachycardia only in male rats. These parameters, except for hemodynamic changes, were restored to near-control levels 1 day after single LPS dosing. The 2-days dosing with LPS had no effects on renal function biomarkers, but caused hypotension, tachycardia, and increases in renal NF-κB/iNOS expression and NECA and ACh vasodilations in both rat sexes. None of these parameters were different from control values when measured 6 days after the endotoxic insult. Alternatively, the rat mortality was observed during first 2 days of the study and was notably higher in male than in female rats. Our data suggest that the frequency and time elapsed after LPS exposure as well as rat sex are important determinants of the magnitude and direction of detrimental effects of endotoxemia.

Nicotine reverses the enhanced renal vasodilator capacity in endotoxic rats: Role of α7/α4β2 nAChRs and HSP70

BACKGROUND

Nicotine alleviates renal inflammation and injury induced by endotoxemia. This study investigated (i) the nicotine modulation of hemodynamic and renal vasodilatory responses to endotoxemia in rats, and (ii) roles of α7 or α4β2-nAChRs and related HSP70/TNFα/iNOS signaling in the interaction.

METHODS

Endotoxemia was induced by ip lipopolysaccharide (5 mg/kg/day, for 2 days) and changes in systolic blood pressure and vasodilator responsiveness of isolated perfused kidney to acetylcholine or 5'-N-ethylcarboxamidoadenosine (NECA, adenosine receptor agonist) were evaluated.

RESULTS

Lipopolysaccharide had no effect on serum creatinine, reduced blood pressure, and increased renal vasodilations induced by acetylcholine or NECA in male and female preparations. Immunohistochemical analyses showed that lipopolysaccharide reduced renal HSP70 expression, but increased α7-nAChRs, α4β2-nAChRs and iNOS expressions. The co-administration of aminoguanidine (iNOS inhibitor), pentoxifylline (TNFα inhibitor), or nicotine attenuated lipopolysaccharide mediation of renal vasodilations and elevations in α7/α4β2-nAChR and iNOS expressions. Nicotine also reversed the downregulating effect of lipopolysaccharide on HSP70 expression. α7-nAChRs (methyllycaconitine citrate, MLA) or α4β2-nAChRs (dihydro-β-erythroidine, DHβE) blockade potentiated the lipopolysaccharide enhancement of renal vasodilations, and abolished the depressant effect of nicotine on lipopolysaccharide responses. A similar abolition of nicotine effects was seen after HSP70 inhibition by quercetin. Alternatively, lipopolysaccharide hypotension was eliminated in rats treated with DHβE/nicotine or quercetin/nicotine regimen in contrast to no effect for nicotine alone or combined with MLA.

CONCLUSIONS

These findings establish that nicotine offsets lipopolysaccharide facilitation of renal vasodilations possibly through a crosstalk between HSP70 and nAChRs of the α7 and α4β2 types.

Salvinorin A preserves cerebral pial artery autoregulation after forebrain ischemia via the PI3K/AKT/cGMP pathway

This study aimed to investigate the protective effect of salvinorin A on the cerebral pial artery after forebrain ischemia and explore related mechanisms. Thirty Sprague-Dawley rats received forebrain ischemia for 10 min. The dilation responses of the cerebral pial artery to hypercapnia and hypotension were assessed in rats before and 1 h after ischemia. The ischemia reperfusion (IR) control group received DMSO (1 µL/kg) immediately after ischemia. Two different doses of salvinorin A (10 and 20 µg/kg) were administered following the onset of reperfusion. The 5th, 6th, and 7th groups received salvinorin A (20 µg/kg) and LY294002 (10 µM), L-NAME (10 μM), or norbinaltorphimine (norBIN, 1 μM) after ischemia. The levels of cGMP in the cerebrospinal fluid (CSF) were also measured. The phosphorylation of AKT (p-AKT) was measured in the cerebral cortex by western blot at 24 h post-ischemia. Cell necrosis and apoptosis were examined by hematoxylin-eosin staining (HE) and TUNEL staining, respectively. The motor function of the rats was evaluated at 1, 2, and 5 days post-ischemia. The dilation responses of the cerebral pial artery were significantly impaired after ischemia and were preserved by salvinorin A treatment. In addition, salvinorin A significantly increased the levels of cGMP and p-AKT, suppressed cell necrosis and apoptosis of the cerebral cortex and improved the motor function of the rats. These effects were abolished by LY294002, L-NAME, and norBIN. Salvinorin A preserved cerebral pial artery autoregulation in response to hypercapnia and hypotension via the PI3K/AKT/cGMP pathway.

Anti-inflammatory and antithrombotic effects of nicotine exposure in oral contraceptive-induced insulin resistance are glucocorticoid-independent

BACKGROUND

Reports showed that estrogen-progestin oral contraceptive (COC) or tobacco smoking causes increased risk of cardiovascular diseases (CVD) in premenopausal women. Studies also suggest that nicotine, a major tobacco alkaloid, may worsen or improve atherothrombotic CVD. Altered hemorheology, prothrombotic and pro-inflammatory biomarkers, have been implicated in the development of atherothrombotic CVD events. However, the effect of non-smoking nicotine exposure on these biomarkers during COC treatment is not yet established. We therefore sought to determine the effects of nicotine exposure during COC treatment on these biomarkers, and also tested the hypothesis that the nicotine effects would be glucocorticoid-dependent.

METHODS

Female Sprague-Dawley rats aged 10 weeks were given (po) vehicle, low-dose nicotine (0.1mg/kg) or high-dose nicotine (1.0mg/kg) with or without COC steroids (5.0μg/kg ethinylestradiol and 25.0μg/kg levonorgestrel) daily for 6 weeks.

RESULTS

COC treatment or nicotine exposure led to increased insulin resistance (IR), hemorheological (blood viscosity, hematocrit and plasma viscosity), prothrombotic (plasminogen activator inhibitor-1), pro-inflammatory (uric acid, C-reactive protein, neutrophil/lymphocyte and platelet/lymphocyte ratios) biomarkers and corticosterone. However, these effects except that on corticosterone were abrogated by nicotine exposure during COC treatment.

CONCLUSIONS

Our study indicates that nicotine- or COC-induced IR may be mediated via inflammatory/thrombotic pathway. The results imply that nicotine exposure could impact negatively on atherothrombotic biomarkers in COC non-users, whereas the impact in COC users could be positive. The results also suggest that the anti-inflammatory, antithrombotic and blood viscosity-lowering effects of nicotine exposure during COC use is circulating glucocorticoid-independent.

Ovarian hormones modulate endothelin A and B receptor expression

AIMS

The study aims to determine the modulatory roles of ovarian hormones, estrogen (E2) and progesterone (P), on the expression of endothelin A (ETA) and B (ETB) receptors in lung, liver and kidney tissues.

MAIN METHODS

Female Sprague-Dawley rats were subjected to bilateral ovariectomy and divided into four groups ovariectomized (OVX), OVX+E2, OVX+P, and OVX+E2+P. A separate group of rats underwent sham surgery and served as a control. Three weeks after OVX or sham surgery, tissues from lungs, liver, renal cortex, and inner medulla were collected, snap-frozen, and kept at -80°C for assessment of ETA and ETB receptor expression using real-time PCR.

KEY FINDINGS

E2-treated OVX animals had significantly lower expression of ETA receptors in the lungs, compared to OVX rats. Pulmonary ETB receptor mRNA was not measurably affected by any of the interventions. Hepatic ETA and ETB were significantly increased in OVX+E2+P rats, compared to sham rats. Renal inner medullary ETA and ETB receptor expressions were significantly elevated in OVX compared to sham, an effect that was prevented by co-supplementation of OVX with E2 and P. Additionally, both ETA and ETB receptor expression in the renal cortex were significantly attenuated by ovariectomy, and this reduction was not evident in OVX+E2 rats.

SIGNIFICANCE

These data suggest that ovarian hormones regulate ET receptor expression and may contribute to sex differences in cardiovascular and renal health.

Punicalagin Induces Nrf2/HO-1 Expression via Upregulation of PI3K/AKT Pathway and Inhibits LPS-Induced Oxidative Stress in RAW264.7 Macrophages

Reactive oxygen species (ROS) and oxidative stress are thought to play a central role in potentiating macrophage activation, causing excessive inflammation, tissue damage, and sepsis. Recently, we have shown that punicalagin (PUN) exhibits anti-inflammatory activity in LPS-stimulated macrophages. However, the potential antioxidant effects of PUN in macrophages remain unclear. Revealing these effects will help understand the mechanism underlying its ability to inhibit excessive macrophage activation. Hemeoxygenase-1 (HO-1) exhibits antioxidant activity in macrophages. Therefore, we hypothesized that HO-1 is a potential target of PUN and tried to reveal its antioxidant mechanism. Here, PUN treatment increased HO-1 expression together with its upstream mediator nuclear factor-erythroid 2 p45-related factor 2 (Nrf2). However, specific inhibition of Nrf2 by brusatol (a specific Nrf2 inhibitor) dramatically blocked PUN-induced HO-1 expression. Previous research has demonstrated that the PI3K/Akt pathway plays a critical role in modulating Nrf2/HO-1 protein expression as an upstream signaling molecule. Here, LY294002, a specific PI3K/Akt inhibitor, suppressed PUN-induced HO-1 expression and led to ROS accumulation in macrophages. Furthermore, PUN inhibited LPS-induced oxidative stress in macrophages by reducing ROS and NO generation and increasing superoxide dismutase (SOD) 1 mRNA expression. These findings provide new perspectives for novel therapeutic approaches using antioxidant medicines and compounds against oxidative stress and excessive inflammatory diseases including tissue damage, sepsis, and endotoxemic shock.