Nicotinic acetylcholine receptor expression and regulation in the rat kidney after ischemia-reperfusion injury

Targeted Polymersomes Enable Enhanced Delivery to Peripheral Nerves Post-Injury

The gold standard therapy for peripheral nerve injuries involves surgical repair, which is invasive and leads to major variations in therapeutic outcomes. Because of this, smaller injuries often go untreated. However, alternative, noninvasive routes of administration are currently unviable due to the presence of the blood-nerve barrier (BNB), which prevents passage of small molecules from the blood into the endoneurium and the nerve. This paper demonstrates that ligands on the surface of nanoparticles, called polymersomes, can enable delivery to the nerve through noninvasive intramuscular injections. Polymersomes made from polyethylene glycol (PEG)-b-polylactic acid (PLA) were conjugated with either apolipoprotein E (ApoE) or rabies virus glycoprotein-based peptide RVG29 (RVG) and loaded with near-infrared dye, AlexaFluor647. ApoE was used to target receptors upregulated in post-injury inflammation, while RVG targets neural-specific receptors. Untagged, ApoE-tagged, and RVG-tagged polymersomes were injected at 100 mM either intranerve (IN) or intramuscular (IM) into Sprague-Dawley rats post sciatic nerve injury. The addition of the ApoE and RVG tags enabled increased AlexaFluor647 fluorescence in the injury site at 1 h post IN injection compared to the untagged polymersome control. However, only the RVG-tagged polymersomes increased the AlexaFluor647 fluorescence after IM injection. Ex vivo analysis of sciatic nerves demonstrated that ApoE-tagged polymersomes enabled the greatest retention of AlexaFluor647 regardless of the injection route. This led us to conclude that using ApoE to target inflammation enabled the greatest retention of polymersome-delivered payloads while using RVG to target neural cells more specifically enabled the penetration of polymersome-delivered payloads. Observations were confirmed by calculating the area under the curve pharmacokinetic parameters and the use of a two-compartment pharmacokinetic model.

The "double-edged sword effect" of nicotine

As the main effect substances of tobacco products, the physiological effects of nicotine have attracted the attention of researchers, especially in recent years, the discussion on the benefits and harms of nicotine (or tobacco products) has become increasingly fierce. In this review, the structure, distribution and physiological effects of nicotinic acetylcholine receptor (nAchR) are summarized. The absorption, distribution, metabolism and excretion of nicotine in the body were introduced. Further, the positive effects of low-dose and short-term nicotine exposure on mitochondrial function regulation, stem cell proliferation and differentiation, nervous system protection and analgesia were elucidated. At the same time, it is also discussed that high-dose and long-term nicotine exposure can activate the oxidative stress effect, mediate abnormal epigenetic modification, and enhance the immune inflammatory response, and then produce negative effects on the body. To sum up, this review suggests that there is a "double-edged sword" effect of nicotine, which on the one hand helps people to understand the physiological effects of nicotine more comprehensively and carefully, and on the other hand provides some theoretical basis for the rational use of nicotine and the innovative development of related products.

Nicotinic acetylcholine receptor-mediated effects of varenicline on LPS-elevated prostaglandin and cyclooxygenase levels in RAW 264.7 macrophages

Introduction: The purpose of this study is to delineate anti-inflammatory and antioxidant potential of varenicline, a cigarette smoking cessation aid, on decreasing lipopolysaccharide (LPS)-elevated proinflammatory cytokines in RAW 264.7 murine macrophage cultures which we showed earlier to occur via cholinergic anti-inflammatory pathway (CAP) activation. To this end, we investigated the possible suppressive capacity of varenicline on LPS-regulated cyclooxygenase (COX-1 and COX-2) via α7 nicotinic acetylcholine receptor (α7nAChR) activation using the same in vitro model. Materials and Methods: In order to test anti-inflammatory effectiveness of varenicline, the levels of COX isoforms and products (PGE2, 6-keto PGF1α, a stable analog of PGI2, and TXA2) altered after LPS administration were determined by Enzyme Linked Immunosorbent Assay (ELISA). The antioxidant effects of varenicline were assessed by measuring reductions in reactive oxygen species (ROS) using a fluorometric intracellular ROS assay kit. We further investigated the contribution of nAChR subtypes by using non-selective and/or selective α7nAChR antagonists. The results were compared with that of conventional anti-inflammatory medications, such as ibuprofen, celecoxib and dexamethasone. Results: Varenicline significantly reduced LPS-induced COX-1, COX-2 and prostaglandin levels and ROS to an extent similar to that observed with anti-inflammatory agents used. Discussion: Significant downregulation in LPS-induced COX isoforms and associated decreases in PGE2, 6-keto PGF1α, and TXA2 levels along with reduction in ROS may be partly mediated via varenicline-activated α7nAChRs.

Syndecan-1 shedding destroys epithelial adherens junctions through STAT3 after renal ischemia/reperfusion injury

Adherens junctions between tubular epithelial cells are disrupted in renal ischemia/reperfusion (I/R) injury. Syndecan-1 (SDC-1) is involved in maintaining cell morphology. We aimed to study the role of SDC-1 shedding induced by renal I/R in the destruction of intracellular adherens junctions. We found that SDC-1 shedding was increased while the expression of E-cadherin was decreased. This observation was accompanied by the activation of STAT3 in the kidneys. Inhibiting the shedding of SDC-1 induced by I/R could alleviate this effect. Mild renal I/R could induce more severe renal injury, lower E-cadherin expression, damaged cell junctions, and activated STAT3 in knockout mice with the tubule-specific deletion of SDC-1 mice. The results in vitro were consistent with those in vivo. Inhibiting the shedding of SDC-1 could alleviate the decreased expression of E-cadherin and damage of cell adherens junctions through inhibiting the activation of STAT3 during ischemic acute kidney injury.

Using RNA-based therapies to target the kidney in cardiovascular disease

RNA-based therapies are currently used for immunisation against infections and to treat metabolic diseases. They can modulate gene expression in immune cells and hepatocytes, but their use in other cell types has been limited by an inability to selectively target specific tissues. Potential solutions to this targeting problem involve packaging therapeutic RNA molecules into delivery vehicles that are preferentially delivered to cells of interest. In this review, we consider why the kidney is a desirable target for RNA-based therapies in cardiovascular disease and discuss how such therapy could be delivered. Because the kidney plays a central role in maintaining cardiovascular homeostasis, many extant drugs used for preventing cardiovascular disease act predominantly on renal tubular cells. Moreover, kidney disease is a major independent risk factor for cardiovascular disease and a global health problem. Chronic kidney disease is projected to become the fifth leading cause of death by 2040, with around half of affected individuals dying from cardiovascular disease. The most promising strategies for delivering therapeutic RNA selectively to kidney cells make use of synthetic polymers and engineered extracellular vesicles to deliver an RNA cargo. Future research should focus on establishing the safety of these novel delivery platforms in humans, on developing palatable routes of administration and on prioritising the gene targets that are likely to have the biggest impact in cardiovascular disease.

The controversial effect of smoking and nicotine in SARS-CoV-2 infection

The effects of nicotine and cigarette smoke in many diseases, notably COVID-19 infection, are being debated more frequently. The current basic data for COVID-19 is increasing and indicating the higher risk of COVID-19 infections in smokers due to the overexpression of corresponding host receptors to viral entry. However, current multi-national epidemiological reports indicate a lower incidence of COVID-19 disease in smokers. Current data indicates that smokers are more susceptible to some diseases and more protective of some other. Interestingly, nicotine is also reported to play a dual role, being both inflammatory and anti-inflammatory. In the present study, we tried to investigate the effect of pure nicotine on various cells involved in COVID-19 infection. We followed an organ-based systematic approach to decipher the effect of nicotine in damaged organs corresponding to COVID-19 pathogenesis (12 related diseases). Considering that the effects of nicotine and cigarette smoke are different from each other, it is necessary to be careful in generalizing the effects of nicotine and cigarette to each other in the conducted researches. The generalization and the undifferentiation of nicotine from smoke is a significant bias. Moreover, different doses of nicotine stimulate different effects (dose-dependent response). In addition to further assessing the role of nicotine in COVID-19 infection and any other cases, a clever assessment of underlying diseases should also be considered to achieve a guideline for health providers and a personalized approach to treatment.

The emergence of the uniquely human α7 nicotinic acetylcholine receptor gene and its roles in inflammation

The uniquely human CHRFAM7A gene is evolved from the fusion of two partially duplicated genes, ULK4 and CHRNA7. Transcription of CHRFAM7A gene produces a 1256-bp open reading frame (ORF) that encodes duplicate α7-nAChR (dup-α7-nAChR), in which a 27-aminoacid peptide derived from ULK4 gene replaces the 146-aminoacid N-terminal extracellular domain of α7-nAChR, and the rest protein domains are exactly the same as those of α7-nAChR. In vitro, dup-α7-nAChR has been shown to form hetero-pentamer with α7-nAChR and dominant-negatively inhibits the channel functions of the latter. α7-nAChR has been shown to participate in many pathophysiological processes such as cognition, memory, neuronal degenerative disease, psychological disease, and inflammatory diseases, among others, and thus has been extensively exploited as potential therapeutic targets for many diseases. Unfortunately, many lead compounds that showed potent therapeutic effect in preclinical animal models failed clinical trials, suggesting the possibility that the contribution of the uniquely human CHRFAM7A gene may not be accounted for in the preclinical research. Here, we review the emergence of CHRFAM7A gene and its transcriptional regulation, the regulatory roles of CHRFAM7A gene in α7-nAChR-mediated cholinergic anti-inflammatory pathway, and the potential implications of CHRFAM7A gene in translational research and drug discovery.

Xenobiotics Delivered by Electronic Nicotine Delivery Systems: Potential Cellular and Molecular Mechanisms on the Pathogenesis of Chronic Kidney Disease

Chronic kidney disease (CKD) is characterized as sustained damage to the renal parenchyma, leading to impaired renal functions and gradually progressing to end-stage renal disease (ESRD). Diabetes mellitus (DM) and arterial hypertension (AH) are underlying diseases of CKD. Genetic background, lifestyle, and xenobiotic exposures can favor CKD onset and trigger its underlying diseases. Cigarette smoking (CS) is a known modified risk factor for CKD. Compounds from tobacco combustion act through multi-mediated mechanisms that impair renal function. Electronic nicotine delivery systems (ENDS) consumption, such as e-cigarettes and heated tobacco devices, is growing worldwide. ENDS release mainly nicotine, humectants, and flavorings, which generate several byproducts when heated, including volatile organic compounds and ultrafine particles. The toxicity assessment of these products is emerging in human and experimental studies, but data are yet incipient to achieve truthful conclusions about their safety. To build up the knowledge about the effect of currently employed ENDS on the pathogenesis of CKD, cellular and molecular mechanisms of ENDS xenobiotic on DM, AH, and kidney functions were reviewed. Unraveling the toxic mechanisms of action and endpoints of ENDS exposures will contribute to the risk assessment and implementation of proper health and regulatory interventions.

Nicotine has no significant cytoprotective activity against SARS-CoV-2 infection

When coronavirus disease 2019 (COVID-19) became a pandemic, one of most important questions was whether people who smoke are at more risk of COVID-19 infection. A number of clinical data have been reported in the literature so far, but controversy exists in the collection and interpretation of the data. Particularly, there is a controversial hypothesis that nicotine might be able to prevent SARS-CoV-2 infection. In the present study, motivated by the reported controversial clinical data and the controversial hypothesis, we carried out cytotoxicity assays in Vero E6 cells to examine the potential cytoprotective activity of nicotine against SARS-CoV-2 infection and demonstrated for the first time that nicotine had no significant cytoprotective activity against SARS-CoV-2 infection in these cells.

Ropivacaine with intraspinal administration alleviates preeclampsia-induced kidney injury via glycocalyx /alpha 7 nicotinic acetylcholine receptor pathway

Preeclampsia is characterized by hypertension and proteinuria, which is associated with kidney injury. Glycocalyx (GCX) degradation mediated endothelial injury can result in proteinuria and kidney damage. alpha 7 nicotinic acetylcholine receptor (α7nAChR) connects nervous and immune systems to respond to stress or injury. We aimed to explore the protective effect and mechanism of intraspinal analgesia on maternal kidney injury in preeclampsia. Endotoxin-induced preeclampsia rats treated with ropivacaine via intraspinal administration. Renal histopathological examination was performed, cell apoptosis in the kidney, the levels of Glycocalyx markers of Syndecan-1 and heparin sulfate (HS) in maternal serum, Syndecan-1 along with α7nAChR in the kidney were measured. Our results showed that kidney injury was obviously in preeclampsia rats with proteinuria, endothelial damage, higher apoptosis rate, increasing levels of Syndecan-1 and HS in serum, upregulated Syndecan-1 expression but downregulated α7nAChR expression in kidney. Preeclampsia rats treated with intraspinal injected ropivacaine attenuated preeclampsia-induced kidney injury as Syndecan-1 and HS were decreased in serum, Syndecan-1 expression was suppressed as well as α7nAChR was activated in the kidney. Our results suggested that Ropivacaine administered through the spinal canal may protect preeclampsia-induced renal injury by decreasing GCX and α7nAChR activation.

Racial Health Disparity and COVID-19

The infection by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and resultant coronavirus diseases-19 (COVID-19) disproportionally affects minorities, especially African Americans (AA) compared to the Caucasian population. The AA population is disproportionally affected by COVID-19, in part, because they have high prevalence of underlying conditions such as obesity, diabetes, and hypertension, which are known to exacerbate not only kidney diseases, but also COVID-19. Further, a decreased adherence to COVID-19 guidelines among tobacco smokers could result in increased infection, inflammation, reduced immune response, and lungs damage, leading to more severe form of COVID-19. As a result of high prevalence of underlying conditions that cause kidney diseases in the AA population coupled with tobacco smoking make the AA population vulnerable to severe form of both COVID-19 and kidney diseases. In this review, we describe how tobacco smoking interact with SARS-CoV-2 and exacerbates SARS-CoV-2-induced kidney diseases including renal failure, especially in the AA population. We also explore the role of extracellular vesicles (EVs) in COVID-19 patients who smoke tobacco. EVs, which play important role in tobacco-mediated pathogenesis in infectious diseases, have also shown to be important in COVID-19 pathogenesis and organ injuries including kidney. Further, we explore the potential role of EVs in biomarker discovery and therapeutics, which may help to develop early diagnosis and treatment of tobacco-induced renal injury in COVID-19 patients, respectively.

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.

Myasthenia gravis associated with renal cell carcinoma: a paraneoplastic syndrome or just a coincidence

BACKGROUND

Myasthenia gravis (MG) can occur as a paraneoplastic phenomenon associated with thymoma. The association of MG with renal cell carcinoma (RCC) is not clear. Herein, we describe six cases of MG associated with RCC.

METHODS

There were 283 patients diagnosed with MG admitted to our hospital from 2014 to 2019. Among them, 6 patients also had RCC. None of them had immune checkpoint inhibitor therapies. We performed a retrospective clinical data collection and follow-up studies of these 6 patients.

RESULTS

These 6 patients with an average MG onset age of 61.3 ± 13.3 years, were all positive for anti-acetylcholine receptor antibodies. MG symptoms appeared after RCC resection in 3 cases. RCC was discovered after the onset of MG in 2 cases, and synchronously with MG in 1 case. After nephrectomy, the MG symptoms showed a stable complete remission in 1 case. Among them, four patients met the diagnostic criteria of possible paraneoplastic neurological syndromes.

CONCLUSIONS

Except for thymoma, patients with MG should pay attention to other tumors including RCC. MG may be a paraneoplastic syndrome of RCC, and further studies are needed to elucidate the relationship.

The protective effect of α7-nACh receptor and its interaction with 5-HT1B/1D receptors in acute intestinal ischemia-reperfusion injury in rats

Over the past decades, great attention has been given to the nervous system modulating effects on the immune response in inflammation-associated injuries, such as acute intestinal ischemia-reperfusion (IR). Recently, we proved the anti-inflammatory and antioxidant effects of 5-hydroxytryptamine (5-HT)1B/1D receptors in intestinal IR injury in rats. Also, the alpha7 nicotinic acetylcholine (α7-nACh) receptor has anti-inflammatory effects in different inflammation-associated injuries. Starting from these premises, we aimed to examine the function of the α7-nACh receptors and the functional interactions between the anti-inflammatory and antioxidant effects of α7-nACh and 5-HT1B/1D receptors in acute intestinal IR injury. To confirm the expression and localization of α7-nACh receptors on the ileum nerves, an immunofluorescence-based method was applied. Then, intestinal IR injury was induced by 30-min occlusion of superior mesenteric artery and reperfusion for 2 h in rats. Acute systemic administration of α7-nACh receptor agonist PNU-282987 and antagonist methyllycaconitine, and 5-HT1B/1D receptors agonist (sumatriptan) and antagonist (GR127, 935) were used in the model of intestinal IR injury. Finally, biochemical and histological parameters were assessed. Α7-nACh receptors were expressed by 9% on the ileum nerves. Likewise, activation of the α7-nACh receptor showed anti-inflammatory and antioxidant effects in intestinal IR injury but not as well as 5-HT1B/1D receptors. Interestingly, 5-HT1B/1D receptors via attenuation of glutamate (Glu) release indirectly activated the α7-nACh receptor and its protective effects against inflammation and oxidative stress. The protective effect of the α7-nACh receptor on intestinal IR injury was activated indirectly through the 5-HT1B/1D receptors' modulatory impact on Glu release.

The cholinergic anti-inflammatory pathway in chronic kidney disease-review and vagus nerve stimulation clinical pilot study

Inflammation and autonomic dysfunction are common findings in chronic and end-stage kidney disease and contribute to a markedly increased risk of mortality in this patient population. The cholinergic anti-inflammatory pathway (CAP) is a vagal neuro-immune circuit that upholds the homoeostatic balance of inflammatory activity in response to cell injury and pathogens. CAP models have been examined in preclinical studies to investigate its significance in a range of clinical inflammatory conditions and diseases. More recently, cervical vagus nerve stimulation (VNS) implants have been shown to be of potential benefit for patients with chronic autoimmune diseases such as rheumatoid arthritis and inflammatory bowel disease. We have previously shown that dialysis patients have a functional CAP ex vivo. Here we review the field and the potential role of the CAP in acute kidney injury and chronic kidney disease (CKD) as well as in hypertension. We also present a VNS pilot study in haemodialysis patients. Controlling inflammation by neuroimmune modulation may lead to new therapeutic modalities for improved treatment, outcome, prognosis and quality of life for patients with CKD.

Efficient neuronal targeting and transfection using RVG and transferrin-conjugated liposomes

Effective transport of therapeutic nucleic acid to brain has been a challenge for the success of gene therapy for treating brain diseases. In this study, we proposed liposomal nanoparticles modified with brain targeting ligandsfor active brain targeting with enhanced BBB permeation and delivery of genes to brain. We targeted transferrin and nicotinic acetylcholine receptors by conjugating transferrin (Tf) and rabies virus glycoprotein (RVG) peptide to surface of liposomes. Liposomal formulations showed homogeneous particle size and ability to protect plasmid DNA against enzymatic degradation. These nanoparticles were internalized by brain endothelial cells, astrocytes and primary neuronal cells through energy-dependent endocytosis pathways. RVG-Tf coupled liposomes showed superior ability to transfect cells compared to liposomes without surface modification or single modification. Characterization of permeability through blood brain barrier (BBB) and functionality of designed liposomes were performed using an in vitro triple co-culture BBB model. Liposome-RVG-Tf efficiently translocated across in vitro BBB model and, consecutively, transfected primary neuronal cells. Notably, brain-targeted liposomes promoted in vivo BBB permeation. These studies suggest that modifications of liposomes with brain-targeting ligands are a promising strategy for delivery of genes to brain.

The Cholinergic Anti-Inflammatory Pathway as a Conceptual Framework to Treat Inflammation-Mediated Renal Injury

BACKGROUND

The cholinergic anti-inflammatory pathway, positioned at the interface of the nervous and immune systems, is the efferent limb of the "inflammatory reflex" which mainly signals through the vagus nerve. As such, the brain can modulate peripheral inflammatory responses by the activation of vagal efferent fibers. Importantly, immune cells in the spleen express most cholinergic system components such as acetylcholine (ACh), choline acetyltransferase, acetylcholinesterase, and both muscarinic and nicotinic ACh receptors, making communication between both systems possible. In general, this communication down-regulates the inflammation, achieved through different mechanisms and depending on the cells involved.

SUMMARY

With the awareness that the cholinergic anti-inflammatory pathway serves to prevent or limit inflammation in peripheral organs, vagus nerve stimulation has become a promising strategy in the treatment of several inflammatory conditions. Both pharmacological and non-pharmacological methods have been used in many studies to limit organ injury as a consequence of inflammation. Key Messages: In this review, we will highlight our current knowledge of the cholinergic anti-inflammatory pathway, with emphasis on its potential clinical use in the treatment of inflammation-triggered kidney injury.

Nicotine increased VEGF and MMP2 levels in the rat eye and kidney

Chronic cigarette smoking affects many tissues negatively. Nicotine in tobacco has negative effects on tissues, kidneys, and eyes especially, where microcirculation is vitally important for the survival and functioning. It is known that appropriate vascular endothelial growth factor (VEGF) and (matrix metalloproteinase 2) MMP2 levels are required for suitable vascularity and enough microcirculation. The aim of this study was to investigate the effect of nicotine on VEGF and MMP2 levels in kidney and eyes, where microcirculation is very important for their function. The nicotine was given into drinking water, to male and female rats for 6 weeks. During the first 2 weeks, the nicotine concentration was 10 mg/L, then was given at a fixed dose of 20 mg/L until the end of the experiment. The VEGF and MMP2 levels were increased in kidney tissue of both genders as a result of given nicotine. MMP2 levels were also increased in the eye tissue for both genders similarly. However, VEGF levels increased in the eye tissue with nicotine in males, whereas it did not change in females. The use of nicotine made VEGF and MMP2 levels increase in kidney tissue in both genders of rats. This increase in VEGF was observed only in male eye tissue, not in females. According to our findings, it can be suggested that nicotine has negative effects on microvascular circulation by increasing VEGF and MMP2 levels. In addition, it should be pointed out that estrogen might have protective effects on female eye tissue. Further studies are necessary to understand the complex relationship between the role of nicotine and estrogen on eye and kidney tissues.

Cigarette smoke inhalation aggravates diabetic kidney injury in rats

Diabetic kidney disease (DKD) is the leading cause of end-stage kidney disease. Epidemiological studies have demonstrated that cigarette smoke or nicotine is a risk factor for the progression of chronic kidney injury. The present study analyzed the kidney toxicity of cigarette smoke in experimental rats with DKD. Experimental diabetes was induced in 7-week-old Sprague-Dawley rats by a single intraperitoneal injection of streptozotocin (60 mg kg^-1). Four weeks after the induction of diabetes, rats were exposed to cigarette smoke (200 μg L^-1), 4 h daily, and 5 days per week for 4 weeks. Cigarette smoke did not affect the levels of plasma glucose, hemoglobin A1c, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol or non-esterified fatty acids in both control and diabetic rats under the experimental conditions. Cigarette smoke, however, significantly increased diabetes-induced glomerular hypertrophy and urinary kidney injury molecule-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL) excretion, suggesting exacerbation of diabetic kidney injury. Cigarette smoke promoted macrophage infiltration and fibrosis in the diabetic kidney. As expected, cigarette smoke increased oxidative stress in both control and diabetic rats. These data demonstrated that four weeks of exposure to cigarette smoke aggravated the progression of DKD in rats.

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.

Alpha7 nicotinic acetylcholine receptors in lung inflammation and carcinogenesis: Friends or foes?

The lung tissue expresses the cholinergic system including nicotinic acetylcholine receptors (nAChRs) which included in many physiologic and pathologic processes. Mounting evidence revealed that these receptors have important roles in lung carcinogenesis via modulating either stimulatory or inhibitory signaling pathways. Among different members of nicotinic receptors family, alpha7-subtype of nAChR (α7nAChR) is a critical mediator involved in both inflammatory responses and cancers. Several studies have shown that this receptor is the most powerful regulator of responses that stimulate lung cancer processes such as proliferation, angiogenesis, metastasis, and inhibition of apoptosis. Moreover, aside from its roles in the regulation of cancer pathways, there is growing evidence indicating that α7nAChR has profound impacts on lung inflammation through the cholinergic anti-inflammatory pathway. Regarding such diverse effects as well as the critical roles of nicotine as an activator of α7nAChR on lung cancer pathogenesis, its modulation has emerged as a promising target for drug developments. In this review, we aim to highlight the detrimental as well as the possible beneficial influences of α7nAChR downstream signaling cascades in the control of lung inflammation and cancer-associated properties. Consequently, by considering the significant global burden of lung cancer, delineating the complex influences of α7 receptors would be of great interest in designing novel anticancer and anti-inflammatory strategies for the patients suffering from lung cancer.

Sub-acute administration of lower doses of nicotine caused sex-dependent improvement of renal function in Wistar rats

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Exposure to nicotine is associated with sex-dependent variation in electrolyte disturbances.

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Lower doses of sub-acute nicotine administration enhanced renal function.

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Nicotine-enhanced renal function is more pronounced in female than in male Wistar rats.

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Nicotine-enhanced renal function may be mediated through α7-nAchR.

The adverse and beneficial health effects of nicotine (NIC), the major alkaloid found in cigarettes and tobacco, are controversial. Most studies on NIC have focused on its effects on cardiovascular and nervous functions. This study aimed at determining dose- and sex-specific effects of sub-acute (28 days) NIC administration on some indices of kidney function in Wistar rats. Forty rats (20 males and 20 females), 8–9 weeks old (each housed in separate metabolic cage), were used for this study such that graded doses of NIC (1, 2 and 4 mg/kg i.p. for 28 days) were administered to both sexes while each control received distilled water at 0.2 mL/100 g i.p. Blood was collected under ketamine anesthesia (10 mg/kg i.m) for analyses and results obtained were compared at p < 0.05. The result showed beneficial alterations in plasma and urine level of creatinine, urea and uric acid (p < 0.05) as well as plasma and urine electrolyte level (Na⁺ and K⁺) in both sexes (p < 0.05). Also, there was significant improvement in creatinine clearance (p < 0.05) with no appreciable difference in their histological examination. Although these beneficial effects were more pronounced in the female than in the male (p < 0.05), administration at the highest dose showed potentially deleterious alterations from normal beneficial trend (p < 0.05) in both sexes. It was concluded that sub-acute administration of lower doses of NIC improves kidney function of Wistar rats; an effect that was more pronounced in the females than their male counterparts.

Cholinergic and cytoprotective signaling cascades mediate the mitigative effect of erythropoietin on acute radiation syndrome

The present investigation aimed to evaluate the radiomitigative efficacy of the recombinant human erythropoietin (EPO) against acute radiation syndrome (ARS) in a rat model. Rats were irradiated with a single sublethal dose of γ-radiation (7 Gy; total body irradiation; TBI) on the 1st day of experimental course, then received EPO (5000 IU/kg; i.p.) 24 h after irradiation, and rats were observed for 30 days of survival analysis. Administration of EPO improved 30-day survival, alleviated TBI-induced myelosuppression and pancytopenia, by augmenting lymphocytes and other white blood cells in the peripheral blood of rats, while bone marrow and spleen cellularity were restored. EPO post-exposure treatment alleviated hepatotoxicity biomarkers and restored splenic function. EPO abrogated radiation-induced oxidative stress through the upregulation of the cholinergic anti-inflammatory nicotinic acetylcholine receptor (α-7-nAChR) and the pro-survival Janus kinase-2 and signal transducers and activators of transcription JAK-2/STAT-3 signaling mediated via enhancing nuclear factor erythroid-2 related factor-2 (Nrf-2) cytoprotective machinery in liver and spleen of irradiated rats. Moreover, EPO treatment prevented hepatic and splenic apoptosis. The present study establishes the implication of α-7-nAChR-JAK-2/STAT-3-Nrf-2 signaling cascade in the radiomitigative potential of EPO against ARS.

Activation of the cholinergic anti-inflammatory pathway by GTS-21 attenuates cisplatin-induced acute kidney injury in mice

Acute kidney injury (AKI) is the most common side effect of cisplatin, a widely used chemotherapy drug. Although AKI occurs in up to one third of cancer patients receiving cisplatin, effective renal protective strategies are lacking. Cisplatin targets renal proximal tubular epithelial cells leading to inflammation, reactive oxygen species, tubular cell injury, and eventually cell death. The cholinergic anti-inflammatory pathway is a vagus nerve-mediated reflex that suppresses inflammation via α7 nicotinic acetylcholine receptors (α7nAChRs). Our previous studies demonstrated the renoprotective and anti-inflammatory effects of cholinergic agonists, including GTS-21. Therefore, we examined the effect of GTS-21 on cisplatin-induced AKI. Male C57BL/6 mice received either saline or GTS-21 (4mg/kg, i.p.) twice daily for 4 days before cisplatin and treatment continued through euthanasia; 3 days post-cisplatin mice were euthanized and analyzed for markers of renal injury. GTS-21 significantly reduced cisplatin-induced renal dysfunction and injury (p<0.05). GTS-21 significantly attenuated renal Ptgs2/COX-2 mRNA and IL-6, IL-1β, and CXCL1 protein expression, as well as neutrophil infiltration after cisplatin. GTS-21 blunted cisplatin-induced renal ERK1/2 activation, as well as renal ATP depletion and apoptosis (p<0.05). GTS-21 suppressed the expression of CTR1, a cisplatin influx transporter and enhanced the expression of cisplatin efflux transporters MRP2, MRP4, and MRP6 (p<0.05). Using breast, colon, and lung cancer cell lines we showed that GTS-21 did not inhibit cisplatin’s tumor cell killing activity. GTS-21 protects against cisplatin-AKI by attenuating renal inflammation, ATP depletion and apoptosis, as well as by decreasing renal cisplatin influx and increasing efflux, without impairing cisplatin-mediated tumor cell killing. Our results support further exploring the cholinergic anti-inflammatory pathway for preventing cisplatin-induced AKI.

Nicotinic acetylcholine receptor-mediated protection of the rat heart exposed to ischemia reperfusion

Reperfusion injury following acute myocardial infarction is associated with significant morbidity. Activation of neuronal or non-neuronal cholinergic pathways in the heart has been shown to reduce ischemic injury and this effect has been attributed primarily to muscarinic acetylcholine receptors. In contrast, the role of nicotinic receptors, specifically alpha-7 subtype (α7nAChR) in the myocardium remains unknown which offers an opportunity to potentially repurpose several agonists/modulators that are currently under development for neurologic indications. Treatment of ex vivo and in vivo rat models of cardiac ischemia/reperfusion (I/R) with a selective α7nAChR agonist (GTS21) showed significant increases in left ventricular developing pressure, and rates of pressure development without effects on heart rate. These positive functional effects were blocked by co-administration with methyllycaconatine (MLA), a selective antagonist of α7nAChRs. In vivo, delivery of GTS21 at the initiation of reperfusion, reduced infarct size by 42% (p<0.01) and decreased tissue reactive oxygen species (ROS) by 62% (p<0.01). Flow cytometry of MitoTracker Red stained mitochondria showed that mitochondrial membrane potential was normalized in mitochondria isolated from GTS21 treated compared to untreated I/R hearts. Intracellular ATP concentration in cultured cardiomyocytes exposed to hypoxia/reoxygenation was reduced (p<0.001), but significantly increased to normoxic levels with GTS21 treatment, and this was abrogated by MLA pretreatment. Activation of stress-activated kinases, JNK and p38MAPK, were significantly reduced by GTS21 in I/R. We conclude that targeting myocardial 17nAChRs in I/R may provide therapeutic benefit by improving cardiac contractile function through a mechanism that preserves mitochondrial membrane potential, maintains intracellular ATP and reduces ROS generation, thus limiting infarct size.

The Protective Effect of Alpha 7 Nicotinic Acetylcholine Receptor Activation on Critical Illness and Its Mechanism

Critical illnesses and injuries are recognized as major threats to human health, and they are usually accompanied by uncontrolled inflammation and dysfunction of immune response. The alpha 7 nicotinic acetylcholine receptor (α7nAchR), which is a primary receptor of cholinergic anti-inflammatory pathway (CAP), exhibits great benefits for critical ill conditions. It is composed of 5 identical α7 subunits that form a central pore with high permeability for calcium. This putative structure is closely associated with its functional states. Activated α7nAChR exhibits extensive anti-inflammatory and immune modulatory reactions, including lowered pro-inflammatory cytokines levels, decreased expressions of chemokines as well as adhesion molecules, and altered differentiation and activation of immune cells, which are important in maintaining immune homeostasis. Well understanding of the effects and mechanisms of α7nAChR will be of great value in exploring effective targets for treating critical diseases.

Absence of nicotinic acetylcholine receptor α7 subunit amplifies inflammation and accelerates onset of fibrosis: an inflammatory kidney model

Inflammation is regulated by endogenous mechanisms, including anti-inflammatory cytokines, adenosine, and the nicotinic acetylcholine receptor α7 subunit (α7nAChR). We investigated the role of α7nAChR in protection against the progression of tissue injury in a model of severe, macrophage-mediated, cytokine-dependent anti-glomerular basement membrane (GBM) glomerulonephritis (GN), in α7nAChR-deficient (α7(-/-)) mice . At d 7 after the injection of anti-GBM antibody, kidneys from α7(-/-) mice displayed severe glomeruli (P < 0.0001) and tubulointerstitial lesions (P < 0.001) compared to kidneys from WT mice. An important finding was the presence of severe glomerulosclerosis in α7(-/-) mice in this early phase of the disease. Kidneys of α7(-/-) mice showed greater accumulation of inflammatory cells and higher expression of chemokines and cytokines than did those of WT mice. In addition, in α7(-/-) fibrotic kidneys, the expression of fibrin, collagen, TGF-β, and tissue inhibitor of metalloproteinase (TIMP)-2 increased, and the expression of TIMP3 declined. The increase in counterregulatory responses to inflammation in α7(-/-) nephritic kidneys did not compensate for the lack of α7nAChR. These findings indicate that α7nAChR plays a key role in regulating the inflammatory response in anti-GBM GN and that disruption of the endogenous protective α7nAChR amplifies inflammation to accelerate kidney damage and fibrosis.

"Smoker's Paradox" in Patients Treated for Severe Injuries: Lower Risk of Mortality After Trauma Observed in Current Smokers

BACKGROUND

Studies evaluating the effect of smoking status on mortality outcomes in trauma patients have been limited, despite the fact that survival benefits of smoking have been reported in other critical care settings. The phenomenon "smoker's paradox" refers to the observation that following acute cardiovascular events, such as acute myocardial infarction and cardiac arrest, smokers often experience decreased mortality in the hospital setting. The objective of our study was to determine whether smoking imparts a survival benefit in patients with traumatic injuries.

METHODS

We performed a retrospective cohort study that analyzed cases included in the National Trauma Data Bank research dataset. Hierarchical logistic regression analyses were used to determine whether smoking alters the risk of mortality and complications in patients who smoke.

RESULTS

The percentage of patients experiencing mortality differed significantly between smokers (n = 38,564) and nonsmokers (n = 319,249) (1.8% vs. 4.3%, P < .001); however, the percentage experiencing a major complication did not (9.7% vs. 9.6%, P = .763). Regression analyses indicated that smokers were significantly less likely to die during the hospital stay compared to nonsmokers after adjusting for individual and hospital factors (OR = 0.15; CI = 0.10, 0.22). Additionally, smokers were also less likely to develop a major complication than nonsmokers (OR = 0.73, CI = 0.59-0.91).

CONCLUSIONS

Patients who smoke appear to have a much lower risk of in-hospital mortality than nonsmokers. Further investigation into biological mechanisms responsible for this effect should be carried out in order to potentially develop therapeutic applications.

Expression of acetylcholine receptors by experimental rat renal allografts

Chronic allograft injury (CAI) is a major cause for renal allograft dysfunction and characterized by vasculopathies, tubular atrophy, and fibrosis. We demonstrated that numerous leukocytes interact with vascular endothelial cells of allografts and produce acetylcholine, which contributes to vascular remodeling. The cholinergic system might be a promising target for the development of novel therapies. However, neither the cellular mechanisms nor the acetylcholine receptors involved in CAI are known. Kidney transplantation was performed in the Lewis to Lewis and in the Fischer-334 to Lewis rat strain combination, which is an established experimental model for CAI. Expression of nicotinic and muscarinic acetylcholine receptors mRNA was quantified in renal tissue by real-time RT-PCR on days 9 and 42 after surgery. We detected CHRNA2-7, CHRNA10, CHRNB2, CHRNB4, and CHRM1-3 mRNA in normal kidneys and in renal transplants. In contrast, CHRNA9, CHRM4, and CHRM5 mRNA remained below the threshold of detection. In renal allografts, CHRNA3 and CHRNB4 mRNA expression were dramatically reduced compared to isografts. In conclusion, we demonstrated that most acetylcholine receptor subtypes are expressed by normal and transplanted kidneys. Allograft rejection downmodulates CHRNA3 and CHRNB4 mRNA. The role of different acetylcholine receptor subtypes in the development of CAI remains to be established.

Effects of ghrelin on sepsis-induced acute kidney injury: one step forward

BACKGROUND

Among the several disorders induced by sepsis, acute kidney injury (AKI) represents the most important economic burden problem that is associated with high mortality and morbidity rates. The aim of this study was to investigate the anti-inflammatory effects of ghrelin in sepsis-induced AKI and the possible role of vagus nerve.

METHODS

Five groups were included: sham, cecal ligation and puncture (CLP), CLP-ghrelin, CLP-vagotomy and CLP-vagotomy-ghrelin group.

RESULTS

Ghrelin treatment immediately after induction of CLP, significantly improved renal Glomerular filtration rate (GFR), serum creatinine, BUN and renal necrosis score as compared to the unprotected CLP group. In addition, ghrelin significantly decreased renal TNF alpha (111.5 ± 10.35 vs. 291.8 ± 15.8 pg/mg ptn), VCAM1 (6.28 ± 1.7 vs. 12.9 ± 1.2 µ/g ptn) and MPO (0.95 ± 0.13 vs. 2.5 ± 0.4 µ/g ptn) without significant increase in renal IL-10. Those effects were abolished by vagotomy.

CONCLUSION

We concluded that ghrelin could represent new therapeutic window in early treatment of sepsis-induced AKI and this could be mainly due to its anti-inflammatory effects.

Fetal cholinergic anti-inflammatory pathway and necrotizing enterocolitis: the brain-gut connection begins in utero

Necrotizing enterocolitis (NEC) is an acute neonatal inflammatory disease that affects the intestine and may result in necrosis, systemic sepsis and multisystem organ failure. NEC affects 5-10% of all infants with birth weight ≤ 1500 g or gestational age less than 30 weeks. Chorioamnionitis (CA) is the main manifestation of pathological inflammation in the fetus and is strong associated with NEC. CA affects 20% of full-term pregnancies and upto 60% of preterm pregnancies and, notably, is often an occult finding. Intrauterine exposure to inflammatory stimuli may switch innate immunity cells such as macrophages to a reactive phenotype ("priming"). Confronted with renewed inflammatory stimuli during labour or postnatally, such sensitized cells can sustain a chronic or exaggerated production of proinflammatory cytokines associated with NEC (two-hit hypothesis). Via the cholinergic anti-inflammatory pathway, a neurally mediated innate anti-inflammatory mechanism, higher levels of vagal activity are associated with lower systemic levels of proinflammatory cytokines. This effect is mediated by the α7 subunit nicotinic acetylcholine receptor (α7nAChR) on macrophages. The gut is the most extensive organ innervated by the vagus nerve; it is also the primary site of innate immunity in the newborn. Here we review the mechanisms of possible neuroimmunological brain-gut interactions involved in the induction and control of antenatal intestinal inflammatory response and priming. We propose a neuroimmunological framework to (1) study the long-term effects of perinatal intestinal response to infection and (2) to uncover new targets for preventive and therapeutic intervention.

Ultrasound prevents renal ischemia-reperfusion injury by stimulating the splenic cholinergic anti-inflammatory pathway

AKI affects both quality of life and health care costs and is an independent risk factor for mortality. At present, there are few effective treatment options for AKI. Here, we describe a nonpharmacologic, noninvasive, ultrasound-based method to prevent renal ischemia-reperfusion injury in mice, which is a model for human AKI. We exposed anesthetized mice to an ultrasound protocol 24 hours before renal ischemia. After 24 hours of reperfusion, ultrasound-treated mice exhibited preserved kidney morphology and function compared with sham-treated mice. Ultrasound exposure before renal ischemia reduced the accumulation of CD11b(+)Ly6G(high) neutrophils and CD11b(+)F4/80(high) myeloid cells in kidney tissue. Furthermore, splenectomy and adoptive transfer studies revealed that the spleen and CD4(+) T cells mediated the protective effects of ultrasound. Last, blockade or genetic deficiency of the α7 nicotinic acetylcholine receptor abrogated the protective effect of ultrasound, suggesting the involvement of the cholinergic anti-inflammatory pathway. Taken together, these results suggest that an ultrasound-based treatment could have therapeutic potential for the prevention of AKI, possibly by stimulating a splenic anti-inflammatory pathway.

Nicotine signaling and progression of chronic kidney disease in smokers

The deleterious health effects of cigarette smoking are far reaching, and it remains the most important modifiable risk factor for improving overall morbidity and mortality. In addition to being a risk factor for cancer, cardiovascular disease and lung disease, there is strong evidence, both from human and animal studies, demonstrating a role for cigarette smoking in the progression of chronic kidney disease (CKD). Clinical studies have shown a strong correlation between cigarette smoking and worsening CKD in patients with diabetes, hypertension, polycystic kidney disease, and post kidney transplant. Nicotine, in addition to its role in the addictive properties of cigarette smoking, has other biological effects via activation of non-neuronal nicotinic acetylcholine receptors (nAChRs). Several nAChR subunits are expressed in the normal kidney and blockade of the α7-nAChR subunit ameliorates the effects of nicotine in animal models of CKD. Nicotine increases the severity of renal injury in animal models including acute kidney injury, diabetes, acute nephritis and subtotal nephrectomy. The renal effects of nicotine are also linked to increased generation of reactive oxygen species and activation of pro-fibrotic pathways. In humans, nicotine induces transitory increases in blood pressure accompanied by reductions in glomerular filtration rate and effective renal plasma flow. In summary, clinical and experimental evidence indicate that nicotine is at least in part responsible for the deleterious effects of cigarette smoking in the progression of CKD. The mechanisms involved are the subject of active investigation and may result in novel strategies to ameliorate the effects of cigarette smoking in CKD.

Nicotinic acetylcholine receptor agonists attenuate septic acute kidney injury in mice by suppressing inflammation and proteasome activity

Sepsis is one of the leading causes of acute kidney injury (AKI). Septic patients who develop acute kidney injury (AKI) are at increased risk of death. To date there is no effective treatment for AKI or septic AKI. Based on their anti-inflammatory properties, we examined the effects of nicotinic acetylcholine receptor agonists on renal damage using a mouse model of lipopolysaccharide (LPS)-induced AKI where localized LPS promotes inflammation-mediated kidney damage. Administration of nicotine (1 mg/kg) or GTS-21 (4 mg/kg) significantly abrogated renal leukocyte infiltration (by 40%) and attenuated kidney injury. These renoprotective effects were accompanied by reduced systemic and localized kidney inflammation during LPS-induced AKI. Consistent with these observations, nicotinic agonist treatment significantly decreased renal IκBα degradation and NFκB activation during LPS-induced AKI. Treatment of human kidney cells with nicotinic agonists, an NFκB inhibitor (Bay11), or a proteasome inhibitor (MG132) effectively inhibited their inflammatory responses following stimulation with LPS or TNFα. Renal proteasome activity, a major regulator of NFκB-mediated inflammation, was enhanced by approximately 50% during LPS-induced AKI and elevated proteasome activity was significantly blunted by nicotinic agonist administration in vivo. Taken together, our results identify enhanced renal proteasome activity during LPS-induced AKI and the suppression of both proteasome activity and inflammation by nicotinic agonists to attenuate LPS-induced kidney injury.

Renoprotective effects of long-term oral nicotine in a rat model of spontaneous proteinuria

Many proteinuric renal conditions are accompanied by renal inflammation. Nicotine is known to have anti-inflammatory properties and is used in oral form to help subjects quit smoking. A potential anti-inflammatory role of nicotine in proteinuric renal diseases has not been investigated to date. We therefore evaluated the effects of oral nicotine in a rat model of proteinuria-induced renal inflammation. We used a well-established model of adult (24 wk of age) male Munich-Wistar-Frömter rats. Animals were given three different physiological doses of nicotine in drinking water for 28 wk until 52 wk of age (long term). A group without nicotine served as a parallel control. At 52 wk of age, the control group had a 2.1 times reduction in creatinine clearance, 3.2 times increase in urinary protein excretion, an increased focal glomerulosclerosis (FGS) score, increased glomerular desmin deposition, decreased glomerular podocin, and a higher accumulation of macrophages and myofibroblasts compared with 24-wk-old animals. Oral treatment with nicotine dose dependently preserved renal function and halted proteinuria progression, which were independent of blood pressure reduction. It also reduced FGS, desmin deposition, podocin loss, and density of renal macrophages and myofibroblasts. Nicotine also reduced the level of gene expression of the renal inflammatory markers monocyte chemoattractant protein and vascular cell adhesion molecule-1. In conclusion, long-term oral nicotine preserved kidney function, reduced proteinuria, reduced renal inflammation, and protected progression of renal structural damage in a rat model of proteinuria. We further suggest evaluating nicotine as a potential additional therapeutic option for treating proteinuric kidney diseases.

Human ghrelin protects animals from renal ischemia-reperfusion injury through the vagus nerve

BACKGROUND

Acute kidney injury secondary to renal ischemia and reperfusion injury is widely prevalent. Ghrelin, which is a stomach-derived peptide, has been shown to be anti-inflammatory. The purpose of this study was to examine whether human ghrelin has any beneficial effects after renal ischemia and reperfusion injury, and if so, whether ghrelin's action in renal ischemia and reperfusion injury is mediated by the vagus nerve.

METHODS

Male adult rats were subjected to renal ischemia and reperfusion by bilateral renal pedicle clamping for 60 min, treated intravenously with human ghrelin (4 nmol/rat) or normal saline (vehicle) immediately after reperfusion. After 24 h, the animals were killed and samples were harvested. In separate groups, subdiaphragmatic vagotomy prior to renal ischemia and reperfusion was performed, treated with human ghrelin or vehicle, and at 24 h, blood and organs were harvested.

RESULTS

Renal ischemia and reperfusion injury caused significant increases in the serum levels of tissue injury markers compared with the sham operation. Human ghrelin treatment attenuated serum creatinine and blood urea nitrogen significantly by 55% and 53%, and liver enzymes (aminotransferase [AST] and alanine aminotransferase [ALT]) by 20% and 24%, respectively, compared with the vehicle-treated groups. Tissue water contents, plasma and kidney interleukin-6, and kidney myeloperoxidase activity were decreased. Bcl-2/Bax ratio was increased, and histology of the kidneys was improved. More importantly, prior vagotomy abolished ghrelin's protective effect in tissue injury markers and tissue water contents in renal ischemia and reperfusion injured animals.

CONCLUSION

Human ghrelin treatment in renal ischemia and reperfusion injured rats attenuated systemic and kidney-specific inflammatory responses. The protection of human ghrelin in renal ischemia and reperfusion injury was mediated by the vagus nerve. These data suggest that ghrelin can be developed as a novel treatment for patients with acute kidney injury induced by renal ischemia and reperfusion injury.

Chronic nicotine exposure exacerbates acute renal ischemic injury

Recent epidemiological reports showed that smoking has a negative impact on renal function and elevates the renal risk not only in the renal patient but perhaps also in the healthy population. Studies suggested that nicotine, a major tobacco alkaloid, links smoking to renal dysfunction. While several studies showed that smoking/chronic nicotine exposure exacerbates the progression of chronic renal diseases, its impact on acute kidney injury is virtually unknown. Here, we studied the effects of chronic nicotine exposure on acute renal ischemic injury. We found that chronic nicotine exposure increased the extent of renal injury induced by warm ischemia-reperfusion as evidenced by morphological changes, increase in plasma creatinine level, and kidney injury molecule-1 expression. We also found that chronic nicotine exposure elevated markers of oxidative stress such as nitrotyrosine as well as malondialdehyde. Interestingly, chronic nicotine exposure alone increased oxidative stress and injury in the kidney without morphological alterations. Chronic nicotine treatment not only increased reactive oxygen species (ROS) production and injury but also exacerbated oxidative stress-induced ROS generation through NADPH oxidase and mitochondria in cultured renal proximal tubule cells. The resultant oxidative stress provoked injury through JNK-mediated activation of the activator protein (AP)-1 transcription factor in vitro. This mechanism might exist in vivo as phosphorylation of JNK and its downstream target c-jun, a component of the AP-1 transcription factor, is elevated in the ischemic kidneys exposed to chronic nicotine. Our results imply that smoking may sensitize the kidney to ischemic insults and perhaps facilitates progression of acute kidney injury to chronic kidney injury.

Nicotinic acetylcholine receptor α1 promotes calpain-1 activation and macrophage inflammation in hypercholesterolemic nephropathy

The nicotinic acetylcholine receptor α1 (nAChRα1) was investigated as a potential proinflammatory molecule in the kidney, given a recent report that it is an alternative urokinase plasminogen activator (uPA) receptor, in addition to the classical receptor uPAR. Two animal models and in vitro monocyte studies were involved: (1) In an ApoE(-/-) mouse model of chronic kidney disease, glomerular-resident cells and monocytes/macrophages were identified as the primary cell types that express nAChRα1 during hypercholesterolemia/uninephrectomy-induced nephropathy. Silencing of the nAChRα1 gene for 4 months (6 months on Western diet) prevented the increases in renal monocyte chemoattractant protein-1 and osteopontin expression levels and F4/80+ macrophage infiltration compared with the nonsilenced mice. These changes were associated with significantly reduced transforming growth factor-β1 mRNA (50% decrease) and α smooth muscle actin-positive (αSMA+) myofibroblasts (90% decrease), better glomerular and tubular basement membranes (GBM/TBM) preservation (threefold less disintegration), and better renal function preservation (serum creatinine 40% lower) in the nAChRα1-silenced mice. The nAChRα1 silencing was also associated with significantly reduced renal tissue calcium deposition (78% decrease) and calpain-1 (but not calpain-2) activation (70% decrease). (2) The nAChRα1 was expressed in vitro by mouse monocyte cell line WEHI-274.1. The silencing of nAChRα1 significantly reduced both calpain-1 and -2 activities, and reduced the degradation of the calpain substrate talin. (3) To further explore the role of calpain-1 activity in hypercholesterolemic nephropathy, disease severities were compared in CAST(-/-)ApoE(-/-) (calpain overactive) mice and ApoE(-/-) mice fed with Western diet for 10 months (n=12). Macrophages were the main cell type of renal calpain-1 production in the model. The number of renal F4/80+ macrophages was 10-fold higher in the CAST(-/-)ApoE(-/-) mice (P<0.05), and was associated with a significantly higher level of αSMA+ cells, increased GBM/TBM destruction, and higher serum creatinine levels. Our studies suggest that the receptor nAChRα1 is an important regulator of calpain-1 activation and inflammation in the chronic hypercholesterolemic nephropathy. This new proinflammatory pathway may also be relevant to other disorders beyond hyperlipidemic nephropathy.

Estrogen dependence of the renal vasodilatory effect of nicotine in rats: role of α7 nicotinic cholinergic receptor/eNOS signaling

AIMS

We recently reported that acute exposure to nicotine vasodilates the renal vasculature of male rats via facilitation of endothelial nitric oxide synthase (eNOS). In this study, we investigated whether this effect of nicotine is sexually dimorphic and the role of estrogen in modulating the nicotine effect.

MAIN METHODS

Nicotine-evoked vasodilation was evaluated in phenylephrine-preconstricted perfused kidneys obtained from male, proestrus female, ovariectomized (OVX) and estrogen-replaced OVX (OVXE(2)) rats.

KEY FINDINGS

Nicotine infusion (5×10(-5), 1×10(-4), and 5×10(-4) M) produced greater concentration-dependent reductions in the renal perfusion pressure (RPP) in an isolated kidney from proestrus females than from males. Inhibition of NOS by N(G)-nitro-L-arginine abolished the nicotine-evoked reduction in RPP and abolished the gender difference in the nicotine effect. Nicotine vasodilation was also attenuated in kidneys isolated from OVX and diestrus rats, models characterized by reduced estrogen levels. Further, estrogen or L-arginine supplementation in OVX rats largely restored the renal vasodilatory response to nicotine. Estrogen receptor blockade by tamoxifen abrogated the enhanced nicotine-evoked vasodilation elicited by E(2) in OVX rats. The nitrite/nitrate levels and protein expressions of eNOS and α(7) nicotinic cholinergic receptor (α(7) nAChRs) were significantly higher in renal tissues of OVXE(2) compared with OVX rats, suggesting a facilitatory effect for E(2) on α(7) nAChRs/eNOS signaling.

SIGNIFICANCE

Estrogen-dependent facilitation of NOS signaling mediates the enhanced vasodilator capacity of nicotine in the renal vasculature of female rats. Preliminary evidence also suggests a potential role for α(7) nAChRs in this estrogen-dependent phenomenon.

Expression of cholinesterases in human kidney and its variation in renal cell carcinoma types

Despite the aberrant expression of cholinesterases in tumours, the question of their possible contribution to tumorigenesis remains unsolved. The identification in kidney of a cholinergic system has paved the way to functional studies, but details on renal cholinesterases are still lacking. To fill the gap and to determine whether cholinesterases are abnormally expressed in renal tumours, paired pieces of normal kidney and renal cell carcinomas (RCCs) were compared for cholinesterase activity and mRNA levels. In studies with papillary RCC (pRCC), conventional RCC, chromophobe RCC, and renal oncocytoma, acetylcholinesterase activity increased in pRCC (3.92 ± 3.01 mU·mg(-1), P = 0.031) and conventional RCC (2.64 ± 1.49 mU·mg(-1), P = 0.047) with respect to their controls (1.52 ± 0.92 and 1.57 ± 0.44 mU·mg(-1)). Butyrylcholinesterase activity increased in pRCC (5.12 ± 2.61 versus 2.73 ± 1.15 mU·mg(-1), P = 0.031). Glycosylphosphatidylinositol-linked acetylcholinesterase dimers and hydrophilic butyrylcholinesterase tetramers predominated in control and cancerous kidney. Acetylcholinesterase mRNAs with exons E1c and E1e, 3'-alternative T, H and R acetylcholinesterase mRNAs and butyrylcholinesterase mRNA were identified in kidney. The levels of acetylcholinesterase and butyrylcholinesterase mRNAs were nearly 1000-fold lower in human kidney than in colon. Whereas kidney and renal tumours showed comparable levels of acetylcholinesterase mRNA, the content of butyrylcholinesterase mRNA was increased 10-fold in pRCC. The presence of acetylcholinesterase and butyrylcholinesterase mRNAs in kidney supports their synthesis in the organ itself, and the prevalence of glycosylphosphatidylinositol-anchored acetylcholinesterase explains the splicing to acetylcholinesterase-H mRNA. The consequences of butyrylcholinesterase upregulation for pRCC growth are discussed.

Attenuation of renal ischemia and reperfusion injury by human adrenomedullin and its binding protein

BACKGROUND

Acute renal failure secondary to ischemia and reperfusion (I/R) injury poses a significant burden on both surgeons and patients. It carries a high morbidity and mortality rate and no specific treatment currently exists. Major causes of renal I/R injury include trauma, sepsis, hypoperfusion, and various surgical procedures. We have demonstrated that adrenomedullin (AM), a novel vasoactive peptide, combined with AM binding protein-1 (AMBP-1), which augments the activity of AM, is beneficial in various disease conditions. However, it remains unknown whether human AM/AMBP-1 provides any beneficial effects in renal I/R injury. The objective of our study therefore was to determine whether administration of human AM/AMBP-1 can prevent and/or minimize damage in a rat model of renal I/R injury.

METHODS

Male adult rats were subjected to renal I/R injury by bilateral renal pedicle clamping with microvascular clips for 60 min followed by reperfusion. Human AM (12 microg/kg BW) and human AMBP-1 (40 microg/kg BW) or vehicle (52 microg/kg BW human albumin) were given intravenously over 30 min immediately following the clip removal (i.e., reperfusion). Rats were allowed to recover for 24 h post-treatment, and blood and renal tissue samples were collected. Plasma levels of AM were measured using a radioimmunoassay specific for rat AM. Plasma AMBP-1 was measured by Western analysis. Renal water content and serum levels of systemic markers of tissue injury were measured. Serum and renal TNF-alpha levels were also assessed.

RESULTS

At 24 h after renal I/R injury, plasma levels of AM were significantly increased while plasma AMBP-1 was markedly decreased. Renal water content and systemic markers of tissue injury (e.g., creatinine, BUN, AST, and ALT) were significantly increased following renal I/R injury. Serum and renal TNF-alpha levels were also increased post injury. Administration of human AM/AMBP-1 decreased renal water content, and plasma levels of creatinine, BUN, AST, and ALT. Serum and renal TNF-alpha levels were also significantly decreased after AM/AMBP-1 treatment.

CONCLUSION

Treatment with human AM/AMBP-1 in renal I/R injury significantly attenuated organ injury and the inflammatory response. Thus, human AM combined with human AMBP-1 may be developed as a novel treatment for patients with acute renal I/R injury.

The ubiquitin-proteasome system in myocardial ischaemia and preconditioning

The ubiquitin-proteasome system (UPS) represents the major pathway for degradation of intracellular proteins. This article reviews the major components and configurations of the UPS including the 26S proteasome and 11S activated proteasome relevant to myocardial ischaemia. We then present the evidence that the UPS is dysfunctional during myocardial ischaemia as well as potential consequences of this, including dysregulation of target substrates, many of them active signalling proteins, and accumulation of oxidized proteins. As part of this discussion, potential mechanisms, including ATP depletion, inhibition by insoluble protein aggregates, and oxidation of proteasome and regulatory particle subunits, are discussed. Finally, the evidence suggesting a role for the UPS in ischaemic preconditioning is presented. Much of this is inferential but clearly indicates the need for additional research.

Cholinergic agonists regulate JAK2/STAT3 signaling to suppress endothelial cell activation

The cholinergic anti-inflammatory pathway is a physiological mechanism that inhibits cytokine production and minimizes tissue injury during inflammation. Previous investigations revealed that cholinergic stimulation (via cholinergic agonists and vagus nerve stimulation) suppresses endothelial cell activation and leukocyte recruitment. The purpose of this study was to investigate the mechanisms by which cholinergic agonists (e.g., nicotine and GTS-21) regulate endothelial cell activation. Specifically, we examined the effects of cholinergic agonists on IL-6-mediated endothelial cell activation through the JAK2/STAT3 signaling pathway. Treatment of macrovascular human umbilical vein endothelial cells (HUVECs) and microvascular endothelial cells (MVECs) with the cholinergic agonists nicotine and GTS-21 significantly reduced IL-6-mediated monocyte chemoattractant protein-1 (MCP-1) production and ICAM-1 expression which are regulated through the JAK2/STAT3 pathway. We found that treatment of endothelial cells with cholinergic agonists significantly reduced STAT3 activation by phosphorylation and DNA binding. The inhibition of STAT3 phosphorylation was reversed by sodium orthovanadate, an inhibitor of tyrosine phosphatases, as well as by NSC-87877 suggesting a SHP1/2-dependent mechanism. Further investigations showed that cholinergic agonists reduced the phosphorylation of JAK2, an upstream component of the JAK2/STAT3 pathway. Finally, we observed that nicotine and GTS-21 treatment decreased levels of SOCS3 (suppressor of cytokine signaling; a regulator of the inflammatory activity of IL-6) in activated endothelial cells. These data demonstrate that cholinergic agonists suppress IL-6-mediated endothelial cell activation through the JAK2/STAT3 pathway. Our results have significant implications for better understanding the therapeutic potential of cholinergic agonists for treating IL-6 mediated inflammatory conditions.