The α7-nAChR/heme oxygenase-1/carbon monoxide pathway mediates the nicotine counteraction of renal inflammation and vasoconstrictor hyporeactivity in endotoxic male rats

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.

Electroacupuncture ameliorates gastrointestinal dysfunction by modulating DMV cholinergic efferent signals to drive the vagus nerve in p-MCAO rats

Background

The use of proton pump inhibitors in the acute phase of cerebral infarction may lead to adverse long-term outcomes, this study aims to explore the potential of electroacupuncture (EA) in replacing omeprazole in exerting post-stroke gastrointestinal protection.

Methods

A permanent middle cerebral artery infarction model was established using the modified Longa thread occlusion technique. Gastrointestinal motility, gastrointestinal mucosal damage, cerebral infarct volume, and alterations in choline acetyltransferase (ChAT)-positive neurons within the dorsal motor nucleus of the vagus nerve (DMV) were assessed after 7 days of EA at Zusanli (ST36) or omeprazole intervention. To evaluate the role of the vagal nerve in mitigating post-stroke gastrointestinal dysfunction, we employed subdiaphragmatic vagotomy and the ChAT-specific inhibitor α-NETA. Additionally, we utilized methyllycaconitine (MLA), a selective inhibitor of the α7-type nicotinic acetylcholine receptor (α7nAChR), and PNU282987, an agonist, to identify the target of EA.

Results

EA restored ChAT neurons lost in the DMV, activated the vagus nerve and conferred cerebroprotection while ameliorating gastrointestinal mucosal injury and gastrointestinal motility disorders. In addition, following the administration of the α7nAChR antagonist, the attenuation of gastric mucosal injury and inflammatory factors induced by EA was hindered, although gastrointestinal motility still exhibited improvement.

Conclusion

EA at ST36 promotes the restoration of cholinergic signaling in the DMV of stroke-afflicted rats, and its excitation of the vagal nerve inhibits gastrointestinal inflammation after stroke via α7nAChR, while improvement in gastrointestinal motility could be mediated by other acetylcholine receptors.

The Pharmacological Effect of Hemin in Inflammatory-Related Diseases: A Systematic Review

BACKGROUND

Hemin is clinically used in acute attacks of porphyria; however, recent evidence has also highlighted its capability to stimulate the heme oxygenase enzyme, being associated with cytoprotective, antioxidant, and anti-inflammatory effects. Indeed, current preclinical evidence emphasizes the potential anti-inflammatory role of hemin through its use in animal models of disease. Nevertheless, there is no consensus about the underlying mechanism(s) and the most optimal therapeutic regimens. Therefore, this review aims to summarize, analyze, and discuss the current preclinical evidence concerning the pharmacological effect of hemin.

METHODS

Following the application of the search expression and the retrieval of the articles, only nonclinical studies in vivo written in English were considered, where the potential anti-inflammatory effect of hemin was evaluated.

RESULTS

Forty-nine articles were included according to the eligibility criteria established. The results obtained show the preference of using 30 to 50 mg/kg of hemin, administered intraperitoneally, in both acute and chronic contexts. This drug demonstrates significant anti-inflammatory and antioxidant activities considering its capacity for reducing the expression of proinflammatory and oxidative markers.

CONCLUSIONS

This review highlighted the significant anti-inflammatory and antioxidant effects of hemin, providing a clearer vision for the medical community about the use of this drug in several human diseases.

Morphine aggravates inflammatory, behavioral, and hippocampal structural deficits in septic rats

Although pain and sepsis are comorbidities of intensive care units, reported data on whether pain control by opioid analgesics could alter inflammatory and end-organ damage caused by sepsis remain inconclusive. Here, we tested the hypothesis that morphine, the gold standard narcotic analgesic, modifies behavioral and hippocampal structural defects induced by sepsis in male rats. Sepsis was induced with cecal ligation and puncture (CLP) and behavioral studies were undertaken 24 h later in septic and/or morphine-treated animals. The induction of sepsis or exposure to morphine (7 mg/kg) elicited similar: (i) falls in systolic blood pressure, (ii) alterations in spatial memory and learning tested by the Morris water maze, and (iii) depression of exploratory behavior measured by the new object recognition test. These hemodynamic and cognitive defects were significantly exaggerated in septic rats treated with morphine compared with individual interventions. Similar patterns of amplified inflammatory (IL-1β) and histopathological signs of hippocampal damage were noted in morphine-treated septic rats. Additionally, the presence of intact opioid receptors is mandatory for the induction of behavioral and hemodynamic effects of morphine because no such effects were observed when the receptors were blocked by naloxone. That said, our findings suggest that morphine provokes sepsis manifestations of inflammation and interrelated hemodynamic, behavioral, and hippocampal deficits.

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.

Central α7 and α4β2 nicotinic acetylcholine receptors offset arterial baroreceptor dysfunction in endotoxic rats

Cardiac autonomic neuropathy is a prominent feature of endotoxemia. Given the defensive role of the cholinergic pathway in inflammation, we assessed the roles of central homomeric α7 and heteromeric α4β2 nAChRs in arterial baroreceptor dysfunction caused by endotoxemia in rats. Endotoxemia was induced by i.v. administration of lipopolysaccharides (LPS, 10 mg/kg), and baroreflex activity was measured by the vasoactive method, which assesses reflex chronotropic responses to increments (phenylephrine, PE) or decrements (sodium nitroprusside, SNP) in blood pressure. Shifts caused by LPS in PE/SNP baroreflex curves and associated decreases in baroreflex sensitivity (BRS) were dose-dependently reversed by nicotine (25-100 μg/kg, i.v.). The nicotine effect disappeared after intracisternal administration of methyllycaconitine (MLA) or dihydro-β-erythroidine (DHβE), selective blockers of α7 and α4β2 receptors, respectively. The advantageous effect of nicotine on BRSPE was replicated in rats treated with PHA-543613 (α7-nAChR agonist) or 5-iodo-A-85380 (5IA, α4β2-nAChRs agonist) in dose-dependent fashions. Conversely, the depressed BRSSNP of endotoxic rats was improved after combined, but not individual, treatments with PHA and 5IA. Central α7 and α4β2 nAChR activation underlies the nicotine counteraction of arterial baroreflex dysfunction induced by endotoxemia. Moreover, the contribution of these receptors depends on the nature of the reflex chronotropic response (bradycardia vs. tachycardia).

Manipulation of the inflammatory reflex as a therapeutic strategy

The cholinergic anti-inflammatory pathway is the efferent arm of the inflammatory reflex, a neural circuit through which the CNS can modulate peripheral immune responses. Signals communicated via the vagus and splenic nerves use acetylcholine, produced by Choline acetyltransferase (ChAT)+ T cells, to downregulate the inflammatory actions of macrophages expressing α7 nicotinic receptors. Pre-clinical studies using transgenic animals, cholinergic agonists, vagotomy, and vagus nerve stimulation have demonstrated this pathway's role and therapeutic potential in numerous inflammatory diseases. In this review, we summarize what is understood about the inflammatory reflex. We also demonstrate how pre-clinical findings are being translated into promising clinical trials, and we draw particular attention to innovative bioelectronic methods of harnessing the cholinergic anti-inflammatory pathway for clinical use.

Head-to-Head Comparison of Selected Extra- and Intracellular CO-Releasing Molecules on Their CO-Releasing and Anti-Inflammatory Properties

Over the past decade, a variety of carbon monoxide releasing molecules (CORMs) have been developed and tested. Some CORMs spontaneously release CO once in solution, while others require a trigger mechanism to release the bound CO from its molecular complex. The modulation of biological systems by CORMs depends largely on the spatiotemporal release of CO, which likely differs among the different types of CORMs. In spontaneously releasing CORMs, CO is released extracellularly and crosses the cell membrane to interact with intracellular targets. Other CORMs can directly release CO intracellularly, which may be a more efficient method to modulate biological systems. In the present study, we compared the efficacy of extracellular and intracellular CO-releasing CORMs that either release CO spontaneously or require an enzymatic trigger. The efficacy of such CORMs to modulate HO-1 and VCAM-1 expression in TNF-α-stimulated human umbilical vein endothelial cells (HUVEC) was evaluated.

In-vitro immunomodulatory effects of nicotine on Nitric Oxide, interleukin 1β and interleukin 37 production in human peripheral blood mononuclear cells (PBMC) from patients with Behçet disease

Behçet's disease is a chronic systemic inflammatory disorder associated with a cytokine profile disruption and increased nitric oxide levels. In our current study we sought to evaluate the in-vitro modulatory effect of nicotine, the principal alkaloid of tobacco, on nitric oxide (NO), interleukin 1β (IL-1β) and interleukin 37 (IL-37) production during Behçet's disease. Peripheral blood mononuclear cells cultures were performed with or without nicotine (200 μg/ml). Culture supernatants were harvested after 24 h of incubation. NO, IL-1β and IL-37 measurements were, respectively, performed by modified Griess method and ELISA sandwich. Our results showed that nicotine significantly reduced NO and IL-1β levels in patients with Behçet's disease, while it increased IL-37 production. Our results showed no sex differences in the effects of nicotine on the production of nitric oxide and IL-1β nor IL-37 in PBMC of patients. Our findings suggest that nicotine may provide a potential therapeutic strategy targeting inflammation during Behçet's disease.

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.

Gasotransmitter signaling in energy homeostasis and metabolic disorders

Gasotransmitters are small molecules of gases, including nitric oxide (NO), hydrogen sulfide (H₂S), and carbon monoxide (CO). These three gasotransmitters can be endogenously produced and regulate a wide range of pathophysiological processes by interacting with specific targets upon diffusion in the biological media. By redox and epigenetic regulation of various physiological functions, NO, H₂S, and CO are critical for the maintenance of intracellular energy homeostasis. Accumulated evidence has shown that these three gasotransmitters control ATP generation, mitochondrial biogenesis, glucose metabolism, insulin sensitivity, lipid metabolism, and thermogenesis, etc. Abnormal generation and metabolism of NO, H₂S, and/or CO are involved in various abnormal metabolic diseases, including obesity, diabetes, and dyslipidemia. In this review, we summarized the roles of NO, H₂S, and CO in the regulation of energy homeostasis as well as their involvements in the metabolism of dysfunction-related diseases. Understanding the interaction among these gasotransmitters and their specific molecular targets are very important for therapeutic applications.

Nicotine uncovers endotoxic-like cardiovascular manifestations in female rats: Estrogen and nitric oxide dependency

Endotoxic manifestations are diminished in female populations due to immune boosting actions of sex steroids. Considering that tobacco constituents including nicotine inhibit estrogen synthesis, we tested the hypothesis that nicotine exposure unveils cardiovascular anomalies of endotoxemia in female rats. Studies were undertaken in conscious female rats treated with i.v. lipopolysaccharide (LPS, 10 mg/kg) in absence and presence of nicotine. In contrast to no effects for LPS when used alone, dose-related decreases in blood pressure (BP) and serum estrogen were noted in endotoxic rats treated consequently with nicotine (25, 50, or 100 μg/kg i.v.). Signs of cardiac autonomic dysfunction appeared in LPS/nicotine-treated rats such as (i) decreased time-domain indices of heart rate variability (HRV), e.g. standard deviation of R-R intervals (SDNN) and root mean square of successive differences in R-R interval durations (rMSSD), and (ii) reduced total power of the frequency spectrum and shifted cardiac sympathovagal balance toward sympathetic dominance. Nicotine reversed the LPS-evoked modest rises in serum TNFα and IL-1β while had no effect on associated arterial baroreflex dysfunction, inferring no roles for inflammation or baroreflexes in LPS-nicotine interaction. Estrogen or aminoguanidine (iNOS inhibitor), but not pentoxifylline (TNFα inhibitor), abolished LPS/nicotine hypotension. Together, nicotine acts probably via reducing estrogen availability to uncover nitric oxide-dependent hypotension and autonomic dysregulation in endotoxic female rats.