Suppression by central adenosine A3 receptors of the cholinergic defense against cardiovascular aberrations of sepsis: role of PI3K/MAPKs/NFκB signaling

Introduction: Despite the established role of peripheral adenosine receptors in sepsis-induced organ dysfunction, little or no data is available on the interaction of central adenosine receptors with sepsis. The current study tested the hypothesis that central adenosine A3 receptors (A3ARs) modulate the cardiovascular aberrations and neuroinflammation triggered by sepsis and their counteraction by the cholinergic antiinflammatory pathway.Methods: Sepsis was induced by cecal ligation and puncture (CLP) in rats pre-instrumented with femoral and intracisternal (i.c.) catheters for hemodynamic monitoring and central drug administration, respectively.Results: The CLP-induced hypotension, reduction in overall heart rate variability (HRV) and sympathovagal imbalance towards parasympathetic predominance were abolished by i.v. nicotine (100 μg/kg) or i.c. VUF5574 (A3AR antagonist, 2 µg/rat). In addition, the selective A3AR agonist, 3-iodobenzyl-5′-N-methylcarboxamidoadenosine IB-MECA, 4 µg/rat, i.c.) exaggerated the hypotension and cardiac autonomic dysfunction induced by sepsis and opposed the favorable nicotine actions against these septic manifestations. Immunohistochemically, IB-MECA abolished the nicotine-mediated downregulation of NFκB and NOX2 expression in rostral ventrolateral medullary areas (RVLM) of brainstem of septic rats. The inhibitory actions of IB-MECA on nicotine responses disappeared after i.c. administration of PD98059 (MAPK-ERK inhibitor), SP600125 (MAPK-JNK inhibitor) or wortmannin (PI3K inhibitor). Moreover, infliximab (TNFα inhibitor) eliminated the IB-MECA-induced rises in RVLM-NFκB expression and falls in HRV, but not blood pressure.Conclusion: Central PI3K/MAPKs pathway mediates the A3AR counteraction of cholinergic defenses against cardiovascular and neuroinflammatory aberrations in sepsis

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

Abstract 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

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

We investigated the effect of chronic nicotine on cholinergically-mediated renal vasodilations in female rats and its modulation by the nitric oxide synthase (NOS)/heme oxygenase (HO) pathways. Dose-vasodilatory response curves of acetylcholine (0.01-2.43 nmol) were established in isolated phenylephrine-preconstricted perfused kidneys obtained from rats treated with or without nicotine (0.5-4.0 mg/kg/day, 2 weeks). Acetylcholine vasodilations were potentiated by low nicotine doses (0.5 and 1 mg/kg/day) in contrast to no effect for higher doses (2 and 4 mg/kg/day). The facilitatory effect of nicotine was acetylcholine specific because it was not observed with other vasodilators such as 5'-N-ethylcarboxamidoadenosine (NECA, adenosine receptor agonist) or papaverine. Increases in NOS and HO-1 activities appear to mediate the nicotine-evoked enhancement of acetylcholine vasodilation because the latter was compromised after pharmacologic inhibition of NOS (L-NAME) or HO-1 (zinc protoporphyrin, ZnPP). The renal protein expression of phosphorylated Akt was not affected by nicotine. We also show that the presence of the two ovarian hormones is necessary for the nicotine augmentation of acetylcholine vasodilations to manifest because nicotine facilitation was lost in kidneys of ovariectomized (OVX) and restored after combined, but not individual, supplementation with medroxyprogesterone acetate (MPA) and estrogen (E2). Together, the data suggests that chronic nicotine potentiates acetylcholine renal vasodilation in female rats via, at least partly, Akt-independent HO-1 upregulation. The facilitatory effect of nicotine is dose dependent and requires the presence of the two ovarian hormones

Impairment of Nitric Oxide Synthase but Not Heme Oxygenase Accounts for Baroreflex Dysfunction Caused by Chronic Nicotine in Female Rats

<div><p>We recently reported that chronic nicotine impairs reflex chronotropic activity in female rats. Here, we sought evidence to implicate nitric oxide synthase (NOS) and/or heme oxygenase (HO) in the nicotine-baroreflex interaction. Baroreflex curves relating changes in heart rate to increases (phenylephrine) or decreases (sodium nitroprusside) in blood pressure were generated in conscious female rats treated with nicotine or saline in absence and presence of pharmacological modulators of NOS or HO activity. Compared with saline-treated rats, nicotine (2 mg/kg/day i.p., for 14 days) significantly reduced the slopes of baroreflex curves, a measure of baroreflex sensitivity (BRS). Findings that favor the involvement of NOS inhibition in the nicotine effect were (i) NOS inhibition (<i>N</i>_ω-Nitro-L-arginine methyl ester, L-NAME) reduced BRS in control rats but failed to do so in nicotine-treated rats, (ii) L-arginine, NO donor, reversed the BRS inhibitory effect of nicotine. Alternatively, HO inhibition (zinc protoporphyrin IX, ZnPP) had no effect on BRS in nicotine- or control rats and failed to reverse the beneficial effect of L-arginine on nicotine-BRS interaction. Similar to female rats, BRS was reduced by L-NAME, but not ZnPP, in male rats and the L-NAME effect was not accentuated after concomitant administration of nicotine. Baroreflex dysfunction caused by nicotine in female rats was blunted after supplementation with hemin (HO inducer) but not tricarbonyldichlororuthenium(II) dimer (CORM-2), a carbon monoxide (CO) releasing molecule, or bilirubin, the breakdown product of heme catabolism. The facilitatory effect of hemin was abolished upon simultaneous treatment with L-NAME or 1H-<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0098681#pone.0098681-Lande1" target="_blank">[1]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0098681#pone.0098681-Bullen1" target="_blank">[2]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0098681#pone.0098681-Mancia1" target="_blank">[4]</a> oxadiazolo[4,3-a] quinoxalin-1-one (inhibitor of soluble guanylate cyclase, sGC). The activities of HO and NOS in brainstem tissues were also significantly increased by hemin. Thus, the inhibition of NOS, but not HO, accounts for the baroreflex depressant of chronic nicotine. Further, hemin alleviates the nicotine effect through a mechanism that is NOS/sGC but not CO or bilirubin-dependent.</p></div

Effect of ZnPP (HO inhibitor), hemin (HO inducer), CORM-2 (CO releasing molecule), or ODQ (guanylate cyclase inhibitor) on baroreflex sensitivity (slopes of baroreflex curves) measured by sodium nitroprusside and phenylephrine in conscious, female rats treated for 14 days with nicotine (2 mg/kg/day, i.p.) or its vehicle (saline).

<p>Values are means ± SEM of 6–8 observations. ^*P<0.05 vs. control (saline/saline), ⁺P<0.05 vs. nicotine, ^#P<0.05 vs. nicotine/hemin.</p

Effect of nicotine (0.5–4 mg/kg/day, 2 weeks) on areas under the curves (AUC, %vasodilation.nmol) of the cumulative renal vasodilatory effect of acetylcholine (0.01–2.43 nmol), NECA (1.6–50 nmol), and papaverine (1–2.43 nmol) in phenylephrine (10 µM)-preconstricted isolated perfused kidneys obtained from sham rats.

<p>Values are means±S.E.M. of 6–8 observations. ^*P<0.05 vs. saline values.</p

The effects of inhibition of NOS (L-NAME, 100 µM, panel A) and HO (ZnPP, 1 µM, panel B) on vasodilatory effects of acetylcholine (0.01–2.43 nmol) in phenylephrine (10 µM)-preconstricted isolated perfused kidneys obtained from sham rats treated with nicotine (1 mg/kg/day, 2 weeks) or equal volume of saline.

<p>The effects of L-arginine (NOS substrate, 100 µM), hemin (HO inducer, 100 µM), or wortmannin (100 nM) are also shown. Panel C shows areas under the curves (AUC, %vasodilation.nmol) of the acetylcholine vasodilatory response. Values are means±S.E.M. of 6–8 observations. ^*P<0.05 vs. saline values, ⁺P<0.05 vs. nicotine values, ^$P<0.05 vs. saline/L-NAME values.</p

Effect of nicotine (1 mg/kg/day, 2 weeks) on vasodilatory effects of acetylcholine (0.01–2.43 nmol) in phenylephrine (10 µM)-preconstricted isolated perfused kidneys obtained from sham, or ovariectomized (OVX) rats supplemented with estrogen (OVX/E2), medroxyprogesterone acetate (OVX/MPA), their combination (OVX/E2/MPA), or the vehicle. Values are means±S.E.M. of 6–8 observations.

<p>^*P<0.05 vs. corresponding control values.</p

Effect of nicotine (0.5–4 mg/kg/day, 2 weeks) on cumulative vasodilatory effects of acetylcholine (0.01–2.43 nmol), NECA (1.6–50 nmol), and papaverine (1–2.43 nmol) in phenylephrine (10 µM)-preconstricted isolated perfused kidneys obtained from sham rats.

<p>Vasodilator responses are expressed as percentages of the phenylephrine-induced tone. Values are means±S.E.M. of 6–8 observations. ^*P<0.05 vs. saline values.</p

Cumulative vasodilatory effects of acetylcholine (0.01–2.43 nmol) in phenylephrine (10 µM)-preconstricted isolated perfused kidneys obtained from sham, ovariectomized (OVX) rats supplemented with estrogen (OVX/E2), medroxyprogesterone acetate (OVX/MPA), their combination (OVX/E2/MPA), or the vehicle.

<p>Acetylcholine responses are expressed as percentages of the phenylephrine-induced tone. Values are means±S.E.M. of 6–8 observations. ^*P<0.05 vs. OVX values.</p