Involvement of nitric oxide with activation of Toll-like receptor 4 signaling in mice with dextran sodium sulfate-induced colitis

Ulcerative colitis is an inflammatory bowel disease characterized by acute inflammation, ulceration, and bleeding of the colonic mucosa. Its cause remains unknown. Increases in adhesion molecules in vascular endothelium, and activated neutrophils releasing injurious molecules such as reactive oxygen species, are reportedly associated with the pathogenesis of dextran sodium sulfate (DSS)-induced colitis. Nitric oxide (NO) production derived from inducible NO synthase (iNOS) via activation of nuclear factor κB (NF-κB) has been reported. It is also reported that stimulation of Toll-like receptor 4 (TLR4) by lipopolysaccharide can activate NF-κB. In this study, we investigated the involvement of NO production in activation of the TLR4/NF-κB signaling pathway in mice with DSS-induced colitis. The addition of 5% DSS to the drinking water of male ICR mice resulted in increases in TLR4 protein in colon tissue and NF-κB p65 subunit in the nuclear fraction on day 3, increases in colonic tumor necrosis factor-α on day 4, and increases in P-selectin, intercellular adhesion molecule-1, NO₂⁻/NO₃⁻, and nitrotyrosine in colonic mucosa on day 5. These activated inflammatory mediators and pathology of colitis were completely suppressed by treatment with a NO scavenger, 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, as well as an iNOS inhibitor, aminoguanidine. Conversely, a NO-releasing compound, NOC-18, increased TLR4 levels and nuclear translocation of NF-κB p65 and exacerbated mucosal damage induced by DSS challenge. These data suggest that increases in TLR4 expression induced by drinking DSS-treated water might be directly or indirectly associated with NO overproduction.     

一氧化氮在炎性疼痛中的作用

一氧化氮（nitric oxide,NO）是细胞内重要的信使分子和神经递质,它参与多种生命活动,包括炎性疼痛.NO对炎性疼痛的发展和维持起到了重要的作用.研究NO在疼痛中所起到的作用及其机制有利于阐明痛觉生理和发现疼痛治疗的新手段.目前研究表明,脊髓水平NO参与炎性疼痛调制的可能机制主要有NO/cGMP途径、参与调控即刻早期基因、与其他神经递质的协同作用.另外研究表明,3种类型的一氧化氮合酶（nitric oxide synthases,NOS）在炎性疼痛过程中被激活或者有不同程度的增强表达.     

Inhibition of myeloid differentiation 1 specifically in colon with antisense oligonucleotide exacerbates dextran sodium sulfate-induced colitis

Myeloid differentiation 1 (MD-1), also known as lymphocyte antigen 86 (Ly86), is a soluble protein homologous to MD-2 and forms a complex with radioprotective 105 (RP105). RP105/MD-1 complex negatively regulates toll-like receptor 4 (TLR4) signaling and is involved in several immune disorders. However, the precise role of MD-1 in inflammatory bowel diseases (IBD) remains poorly understood. To further investigate the involvement of MD-1 in IBD, we inhibited MD-1 in colon with antisense oligonucleotide (AS-ODN) and assessed the effect of MD-1 inhibition on dextran sodium sulfate (DSS)-induced colitis. We discovered that MD-1 protein expression was remarkably decreased in both patients with ulcerative colitis and mice with DSS-induced colitis. For the first time, we showed that oral administration of MD-1 AS-ODN to mice significantly suppressed the MD-1 protein levels in colon rather than systemic tissues. Subsequently, we found that MD-1 AS-ODN treated mice were more susceptible to DSS-induced colitis based on loss of body weight, colon length, histological scores, and disease activity index. MD-1 inhibition also significantly enhanced inflammatory cytokines production such as IL-6 and IL-1β in colons. Finally, mice treated with MD-1 AS-ODN exhibited increased messenger RNA levels of TLR4 and MyD88 after DSS exposure and showed enhanced nuclear factor (NF)-κB activation compared with the control. Taken together, specifically suppression of MD-1 in colon tissues with AS-ODN exacerbates DSS-induced experimental colitis in mice, which is possibly related to activation of TLR4/NF-κB signaling.     

mTOR inhibitor INK128 attenuates dextran sodium sulfate-induced colitis by promotion of MDSCs on Treg cell expansion

Accumulating evidence has shown that mammalian target of rapamycin (mTOR) pathway and myeloid-derived suppressor cells (MDSCs) are involved in pathogenesis of inflammatory bowel diseases (IBDs). INK128 is a novel mTOR kinase inhibitor in clinical development. However, the exact roles of MDSCs and INK128 in IBD are unclear. Here, we showed that the INK128 treatment enhanced the resistance of mice to dextran sodium sulfate (DSS)–induced colitis and inhibited the differentiation of MDSCs into macrophages. Moreover, interferon (IFN)-α level was elevated in INK128-treated colitis mice. When stimulated with IFN-α in vitro, MDSCs showed a superior immunosuppression activity. Of note, the regulatory T cells (Tregs) increased but Th1 cells decreased in INK128-treated colitis mice. These results indicate that mTOR inhibitor INK128 attenuates DSS-induced colitis via Treg expansion promoted by MDSCs. Our work provides a new evidence that INK128 is potential to be a therapeutic drug on DSS-induced colitis via regulating MDSCs as well as maintaining Treg expansion.     

The role of nitric oxide in inflammatory reactions

Nitric oxide (NO) was initially described as a physiological mediator of endothelial cell relaxation, an important role in hypotension. NO is an intercellular messenger that has been recognized as one of the most versatile players in the immune system. Cells of the innate immune system--macrophages, neutrophils and natural killer cells--use pattern recognition receptors to recognize the molecular patterns associated with pathogens. Activated macrophages then inhibit pathogen replication by releasing a variety of effector molecules, including NO. In addition to macrophages, a large number of other immune-system cells produce and respond to NO. Thus, NO is important as a toxic defense molecule against infectious organisms. It also regulates the functional activity, growth and death of many immune and inflammatory cell types including macrophages, T lymphocytes, antigen-presenting cells, mast cells, neutrophils and natural killer cells. However, the role of NO in nonspecific and specific immunity in vivo and in immunologically mediated diseases and inflammation is poorly understood. This Minireview will discuss the role of NO in immune response and inflammation, and its mechanisms of action in these processes.     

Effect of cinnamon essential oil on gut microbiota in the mouse model of dextran sodium sulfate-induced colitis

Increasing evidence has confirmed that the antimicrobial and anti-inflammatory effects of cinnamon essential oil (CEO) contribute to protection against inflammatory bowel disease (IBD). The dextran sodium sulfate (DSS)-induced colitis mouse model was established to investigate the correlation between the protective effects of CEO and the regulation of intestinal microflora. The symptoms of IBD were assessed by measuring the hemoglobin content, myeloperoxidase activity, histopathological observation, cytokines, and toll-like receptor (TLR4) expression. The alteration of the fecal microbiome composition was analyzed by 16S rRNA gene sequencing. The results indicated that the oral administration of CEO enriched with cinnamaldehyde effectively alleviated the development of DSS-induced colitis. In contrast to the inability of antibiotics to regulate flora imbalance, the mice fed with CEO had an improved diversity and richness of intestinal microbiota, and a modified community composition with a decrease in Helicobacter and Bacteroides and an increase in Bacteroidales_S24-7 family and short-chain fatty acids (SCFA)-producing bacteria (Alloprevotella and Lachnospiraceae_NK4A136_group). Moreover, the correlation analysis showed that TLR4 and tumor necrosis factor-α was positively correlated with Helicobacter, but inversely correlated with SCFA-producing bacteria. These findings indicated from a new perspective that the inhibitory effect of CEO on IBD was closely related to improving the intestinal flora imbalance.     

昆虫一氧化氮及其合酶的研究进展

一氧化氮作为一种重要的信息分子 ,参与调节昆虫嗅觉、视觉、机械感受、发育、机体防御及学习行为。该文从生理、生化、形态定位以及信号转导几方面综述了有关昆虫一氧化氮及其合酶的最新研究进展。     

靛蓝对葡聚糖硫酸钠诱导的溃疡性结肠炎小鼠肠道菌群作用研究

研究靛蓝对葡聚糖硫酸钠（DSS）诱导的溃疡性结肠炎（UC）模型小鼠的干预作用,并分析对小鼠肠道菌群的影响。

实验小鼠分为对照组、模型组、柳氮磺胺吡啶组（125 mg/kg）和靛蓝组（50 mg/kg),每组小鼠各9只。观察给药后小鼠体征并进行疾病活动指数（DAI）评分,通过苏木素―伊红（HE）染色观察小鼠结肠组织切片形态变化,ELISA法检测小鼠血清中IL-6、TNF-α、IL-1β、IL-8和IL-10水平;针对16S rRNA基因V4‒V5区进行高通量测序,分析小鼠肠道内容物的菌群变化。

与模型组相比,靛蓝组小鼠DAI评分降低,病理切片结果显示靛蓝可改善UC小鼠结肠黏膜损伤,减少炎性细胞浸润,血清中促炎因子IL-6、IL-8、IL-1β和TNF-α水平显著降低（t = 4.377 0、5.374 0、12.140 0、5.508 0,P = 0.011 9、0.005 8、0.000 3、0.005 3）,抑炎因子IL-10水平显著升高（t = 3.716 0,P = 0.020 5）。16S rRNA基因测序结果显示,模型组小鼠肠道菌群多样性降低,靛蓝组小鼠肠道菌群多样性升高。

给予靛蓝干预后可有效缓解UC小鼠结肠炎症状,通过降低炎症因子水平和调节UC小鼠肠道菌群平衡达到治疗UC的效果。

     

Paracrine neuroprotective effect of nitric oxide in the developing retina

The retina of newborn rats consists of the ganglion cell layer (GCL), the inner plexiform layer (IPL), the inner nuclear layer (INL) containing amacrine cells and the neuroblastic layer (NBL). In retinal explants, the GCL enters cell death after sectioning of the optic nerve, whereas there is almost no cell death in the NBL. When protein synthesis is inhibited with anisomycin, cell death is blocked in the GCL and induced in the NBL. We tested the roles of nitric oxide (NO) on cell death in the retina in vitro. Either L-arginine, the substrate for NO synthase or the NO donor S:-nitroso-acetylpenicillamine (SNAP) blocked cell death induced by anisomycin in the NBL, but had no effect in the GCL. Sepiapterin, a precursor of the nitric oxide synthase (NOS)-cofactor tetrahydrobiopterin also had a protective effect against anisomycin. The use of 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, an inhibitor of soluble form of guanylyl cyclase, showed that anti-apoptotic effect of SNAP is partially mediated by cGMP generated by activation of guanylyl cyclase. NADPH-diaphorase histochemistry stained cells only in the GCL and INL. Thus, the degenerative effect of anisomycin is observed within the NBL, whereas the localization of NOS is restricted to the GCL and INL. The protective effect of both the NO substrate and cofactor upon cell death induced by anisomycin in the NBL, indicates that NO produced by amacrine and ganglion cells is a paracrine modulator of cell death within the retinal tissue.     

Interaction of caveolin-1, nitric oxide, and nitric oxide synthases in hypoxic human SK-N-MC neuroblastoma cells

Neuroblastoma cells are capable of hypoxic adaptation, but the mechanisms involved are not fully understood. We hypothesized that caveolin-1 (cav-1), a plasma membrane signal molecule, might play a role in protecting neuroblastoma cells from oxidative injury by modulating nitric oxide (NO) production. We investigated the alterations of cav-1, cav-2, nitric oxide synthases (NOS), and NO levels in human SK-N-MC neuroblastoma cells exposed to hypoxia with 2% [O2]. The major discoveries include: (i) cav-1 but not cav-2 was up-regulated in the cells exposed to 15 h of hypoxia; (ii) NO donor 1-[N, N-di-(2-aminoethyl) amino] diazen-1-ium-1, 2-diolate up-regulated the expression of cav-1, whereas the non-selective NOS inhibitor N(G)-nitro-L-arginine methyl ester and inducible NOS (iNOS) inhibitor 1400W each abolished the increase in cav-1 expression in the hypoxic SK-N-MC cells. These results suggest that iNOS-induced NO production contributes to the up-regulation of cav-1 in the hypoxic SK-N-MC cells. Furthermore, we studied the roles played by cav-1 in regulating NO, NOS, and apoptotic cell death in the SK-N-MC cells subjected to 15 h of hypoxic treatment. Both cav-1 transfection and cav-1 scaffolding domain peptide abolished the induction of iNOS, reduced the production of NO, and reduced the rates of apoptotic cell death in the hypoxic SK-N-MC cells. These results suggest that increased expression of cav-1 in response to hypoxic stimulation could prevent oxidative injury induced by reactive oxygen species. The interactions of cav-1, NO, and NOS could be an important signal pathway in protecting the neuroblastoma cells from oxidative injury, contributing to the hypoxic tolerance of neuroblastoma cells.     

Cytotoxicity of IFN-gamma and TNF-alpha for vascular endothelial cell is mediated by nitric oxide

Endothelial cell injury is a critical event in tissue damage accompanying inflammation, in which both inflammatory cytokines and reactive oxygen species may play pivotal roles, although the exact mechanism has not yet been clarified. We found that combined stimulation with interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha) induced both cytotoxicity to murine vascular endothelial cell line F-2 and an increase in nitric oxide (NO). Therefore, in the present study, the implication of NO in cytotoxicity was examined. A potent iNOS-specific inhibitor ONO-1714 completely blocked both cytokine-induced cytotoxicity and NO production. NO scavengers such as carboxy-PTIO and hemoglobin blocked cytotoxicity. Moreover, exogenous NO from NOC 18 also caused cytotoxicity. These results together demonstrated that cytotoxicity of IFN-gamma and TNF-alpha for endothelial cell F-2 was mediated by NO, suggesting a pathogenic role of cytokine-induced NO production in endothelial damage under inflammatory conditions.     

The effect of calcitonin treatment on plasma nitric oxide levels in post-menopausal osteoporotic patients

Several recent studies have revealed a wide role for nitric oxide (NO) in bone metabolism. Low doses of NO cause bone resorption, but higher doses of NO inhibit bone resorbing activity. Cytokines are potent stimulators of NO production. NO is a very short-lived molecules. It exists for only 6-10 s only before it is converted by oxygen and water into the end-products nitrates and nitrites. Osteoporosis is a metabolic bone disease, characterized by a decreased amount of bone and increased susceptibility to fracture. NO may be involved as a mediator of bone disease such as post-menopausal osteoporosis. Calcitonin is a peptide hormone that inhibits bone resorption. The function of calcitonin in some cells is often unclear. In this study 30 post-menopausal osteoporotic women of ages ranging between 55 and 59 years without systemic diseases and free of any drug therapy were included. Twenty of them, randomly chosen, were treated with calcium (500 mg day(-1))+calcitonin (nasal spray 100 U day(-1)) and the other 10 women (control group) were treated with calcium only. This treatment was applied for 6 months and NO values were measured in each of the two groups before and after treatment. Our findings demonstrate that NO regulates osteoclastic bone resorption activity in association with calcitonin.     

Propofol-induced vascular permeability change is related to the nitric oxide signaling pathway and occludin phosphorylation

The present study was undertaken to elucidate the mechanism of intra-arterial propofol-induced vascular permeability change resulting in tissue edema. The mechanism of propofol-induced hyperpermeability was examined in a rat femoral artery injection model. Vascular permeability was determined by measuring the Evans blue content of the dorsal skin of the infused limb at 15, 30, 45 and 60 min after propofol injection. The total content of the tight junction proteins occludin, ZO-1 and claudin-5 under experimental conditions was also determined by western blotting. Intra-arterial injection with propofol resulted in a marked dose-dependent increase in vascular permeability of the rat hindpaw. Pretreatment with 10 mg/kg of N-nitro-l-arginine methyl ester (l-NAME) but not aminoguanidine significantly inhibited the change in vascular permeability after challenge with propofol. Pretreatment with l-arginine and nitroprusside increased the propofol-induced permeability change. Intra-arterial injection of propofol significantly increased occludin phosphorylation after 15 min, which was consistent with the time profile of the vascular permeability change. l-NAME partially reversed the change in occludin phosphorylation, whereas aminoguanidine had no effect compared with that in the controls. Our observations indicate that nitric oxide (NO) is an important mediator in the induction of vascular permeability induced by propofol. Occludin phosphorylation is a determining factor in the vascular permeability change induced by propofol. NO synthase (NOS) inhibitors might be useful in the treatment of accidental intra-arterial injection of propofol, in the reduction of any adverse effects.     

Zinc coadministration attenuates melatonin’s effect on nitric oxide production in mice

Both melatonin (MEL) and zinc (Zn) are considered beneficial for anti-immunosenescence. MEL’s effects on immune functions are partly attributed to an interaction with Zn. However, the augmentation of or interference with MEL’s effects by coadministration of Zn remains unclear. In this study, adult older mice received either MEL (10 μg/mL), Zn (22 μg/mL), MEL+Zn, or null supplementation from drinking water for 3 mo. The results showed that treated mice, irrespective of the type of added chemicals, had higher body-weight gain and body-fat content than control mice. MEL- and Zn-treated mice also had increased serum free fatty acid levels. In addition, the MEL group had decreased serum NO_X (nitrite+nitrate) values. Serum tumor necrosis factor-alpha levels were increased, although nonsignificantly, in mice that received either MEL or Zn supplementation. However, the differences described were not retained in the mice that received MEL+Zn treatment. We conclude that a high-dose Zn coadministration might exert negative influences on MEL’s regulatory effects, at least on nitric oxide production.     

The effect of nitric oxide on glucose metabolism

Nitric oxide (NO) is an important bioactive signaling molecule that mediates a variety of normal physiological functions, which, if altered, could contribute to the genesis of many pathological conditions, including diabetes. In this study, we examined the possible diabetogenicity of NO by noting differences in the cellular binding of insulin in dogs treated with the NO donor, S-nitrosoglutathione (GSNO) compared to captopril-treated controls. GSNO administration resulted in an abnormality in glucose metabolism which was attributed to decreased binding of insulin to its receptor on the cell membrane of mononuclear leucocytes, 11.60 ± 0.60% in GSNO-treated dogs compared with 18.10 ± 1.90% in captopril-treated control (p < 0.05). The decreased insulin binding was attributed to decreased insulin receptor sites per cell, 21.43 ± 2.51 × 10⁴ in GSNO-treated dogs compared with 26.60 ± 1.57 × 10⁴ in captopril-treated controls (p < 0.05). Average affinity analysis of the binding data demonstrated that this decrease in insulin binding was also due to a decrease in average affinity of the receptor on mononuclear leucocytes for insulin. This was evident by a decrease in empty and filled site affinities in GSNO-treated dogs compared with that of captopril-treated dogs (p < 0.05). It appears that GSNO is exerting its effect by decreasing the number of insulin receptor sites and/or decreasing the average receptor affinity. These results provide evidence for a novel role of NO as a modulator of insulin binding and the involvement of NO in the aetiology of diabetes mellitus. (Mol Cell Biochem 263: 29–34, 2004)     

The reduction of Fusobacterium nucleatum in mice is irrelevant to the nitric oxide induced by iNOS

Previously we reported that mice infected recurrently with live Fusobacterim nucleatum (Fn) synthesize a significant amount of NO between 12 hr and 24 hr after the Fn injection. We now investigated whether the NO has the capability of killing Fn, a gram-negative rod periodontal pathogen. The mice were divided into three groups: treated with live bacteria (LB), treated with heat-killed bacteria (HKB) and untreated: normal (N). The Fn reduction, NO production and cell number after Fn injection were then compared in these mice. In the LB group, no Fn was detected at 6 hr, whereas it was still detected in the HKB and N groups at 24 hr as assessed by both colony counts and PCR assays. A significant amount of NO was synthesized in the LB group at 24 hr after the Fn injection. Fn is not killed by SNAP-generated NO in vitro. An increase in the total cell number was accompanied by an increase of the neutrophil numbers in the LB group. Intracellular O2(-) generation (including ONOO(-)) was visualized using dihydrorhodamine (DHR)-123. The peak of O2(-) generation by PEC was shown to be at 3 hr in all 3 groups. The number of O2(-) positive cells in the LB group at 3 hr was remarkably high, and most of them were likely to be neutrophils. The Fn reduction would be performed cooperatively via oxygen dependent and oxygen independent mechanisms. Thus reactive oxygen species (ROS) included in the oxygen dependent mechanism appear to be important for Fn reduction. However the significant amounts of NO derived from the iNOS synthesized in the LB group between 12 hr and 24 hr after injection of LFn were not involved in the Fn reduction.     

The protective effect of nigeglanine on dextran sulfate sodium-induced experimental colitis in mice and Caco-2 cells

Ulcerative colitis (UC) was a nonspecific inflammatory disease. The treatment of UC is imperative. The present study aimed to investigate the effect of nigeglanine on dextran sulfate sodium-induced UC in experimental mice and Caco-2 cells and define the underlying mechanism. The nigeglanine was shown a significant protective effect on the colon, significantly reduced the weight and colon length loss and inhibited intestinal epithelial cell damage. Nigeglanine also reduced proinflammatory factors and increased anti-inflammatory factor production. The results indicate that nigeglanine suppresses the nuclear factor kappa B and mitogen-activated protein kinases pathways in addition to NLRP3 inflammasome action, inhibiting colon epithelial cell pyroptosis. Surprisingly, ZO-1 and occludin protein levels increased with nigeglanine treatment, suggesting that nigeglanine plays a protective role in barrier integrity, reducing colitis progression. The present study suggests that dietary therapy with nigeglanine may be a useful treatment for prophylaxis and palliative UC.     

The participation of nitric oxide in peritoneal exudate cell cytotoxicity of mice by Fusobacterium nucleatum

Previously we reported that mice infected recurrently with live Fusobacterium nucleatum(Fn) synthesize a significant amount of NO between 12 hr and 24 hr after Fn injection. Fn is a gram-negative rod periodontal pathogen. NO could not be induced by heat-killed Fn or in untreated mice. This NO, derived from the iNOS after infection of live Fn, was not involved in the Fn reduction because Fn clearance occurs within 6 hr. We investigated in this study whether this NO was involved in cytotoxicity in peritoneal exudate cells (PEC) in vivo. The mice were divided into two groups: those treated with live Fn (immune) and those left untreated (normal). PEC number, NO production, detection of apoptosis or death cells, and lactate dehydrogenase (LDH) release activity after injection of live Fn were compared in these groups. In the immune group, the increase of the total cell numbers caused by an increase in neutrophils, a significant NO production only after injection of live Fn at 24 hr and identification of iNOS positive macrophages were confirmed. The apoptotic rate was very low and did not increase at 24 hr in vivo. Therefore, apoptosis was seldom relevant to the NO. In the immune group, LDH activity was remarkable high at 24 hr, and dead cells and macrophages phagocytizing cell fragments increased at the same time. Pretreatment of L NMMA, an inhibitor of iNOS, suppressed LDH activity and cell death. Therefore, the NO derived from the iNOS is involved in the cytotoxicity. These results suggest that NO may contribute to the inflammatory response during Fn infection in periodontitis.     

The effect of shock wave lithotripsy on nitric oxide and malondialdehyde levels in plasma and urine samples

Shock wave lithotripsy (SWL) is accepted as the first treatment choice for most urinary stones, but it has adverse effects on the kidneys. The mechanisms underlying shock wave-induced renal injury have been discussed and include shear stress, thermal and cavitation effects and free radical formation. We investigated the effects of SWL on plasma and urinary nitrite, a stable metabolite of nitric oxide (NO), and malondialdehyde (MDA) concentrations. Between February and October 2004, 12 men and 8 women with renal calculi were treated using a Dornier MPL-9000 lithotriptor. The ages ranged from 22 to 45 years (average age: 33.7 years). Plasma and urinary NO and MDA levels were analysed before, immediately after, 30 and 60 min and 24 h after SWL. Plasma NO levels were higher than baseline levels immediately, and at 30, 60 min and 24 h after treatment (p = 0.016, p = 0.031, p = 0.033 and p = 0.045, respectively). Simultaneously, the mean urinary NO levels also showed significant elevation after SWL compared with baseline values, except for 24 h (p = 0.021, p = 0.023 and p = 0.048, respectively). The mean levels of plasma MDA showed statistically significant elevation immediately, and 30 and 60 min after SWL termination compared with pre-SWL values (p = 0.012, p = 0.008 and p = 0.012, respectively). Urinary MDA levels obtained immediately (p = 0.035), and 30 (p = 0.006) and 60 (p = 0.045) min after SWL were increased compared to pre-SWL values. We speculate that SWL treatment causes oxidative stress caused by renal ischemia-reperfusion (I/R) injury. Additionally, the increase of NO production may have prevented renal damage caused by vasoconstriction.