The effect of sildenafil, a phosphodiesterase-5 inhibitor, on acetic acid-induced colonic inflammation in the rat

Cyclic adenosine 3', 5'-monophosphate (cAMP) signaling is a crucial therapeutic target for ulcerative colitis

The pathogenesis of ulcerative colitis (UC), a chronic intestine inflammatory disease primarily affecting adolescents, remains uncertain. Contemporary studies suggest that a confluence of elements, including genetic predispositions, environmental catalysts, dysregulated immune responses, and disturbances in the gut microbiome, are instrumental in the initiation and advancement of UC. Among them, inflammatory activation and mucosal barrier damage caused by abnormal immune regulation are essential links in the development of UC. The impairment of the mucosal barrier is intricately linked to the interplay of various cellular mechanisms, including oxidative stress, autophagy, and programmed cell death. An extensive corpus of research has elucidated that level of cyclic adenosine 3',5'-monophosphate (cAMP) undergo modifications in the midst of inflammation and participate in a diverse array of cellular operations that mitigate inflammation and the impairment of the mucosal barrier. Consequently, a plethora of pharmacological agents are currently under development, with some advancing through clinical trials, and are anticipated to garner approval as novel therapeutics. In summary, cAMP exerts a crucial influence on the onset and progression of UC, with fluctuations in its activity being intimately associated with the severity of the disease's manifestation. Significantly, this review unveils the paramount role of cAMP in the advancement of UC, offering a tactical approach for the clinical management of individuals afflicted with UC.

Exploring the Multifaceted Potential of Sildenafil in Medicine

Phosphodiesterase type 5 (PDE5) is pivotal in cellular signalling, regulating cyclic guanosine monophosphate (cGMP) levels crucial for smooth muscle relaxation and vasodilation. By targeting cGMP for degradation, PDE5 inhibits sustained vasodilation. PDE5 operates in diverse anatomical regions, with its upregulation linked to various pathologies, including cancer and neurodegenerative diseases. Sildenafil, a selective PDE5 inhibitor, is prescribed for erectile dysfunction and pulmonary arterial hypertension. However, considering the extensive roles of PDE5, sildenafil might be useful in other pathologies. This review aims to comprehensively explore sildenafil's therapeutic potential across medicine, addressing a gap in the current literature. Recognising sildenafil's broader potential may unveil new treatment avenues, optimising existing approaches and broadening its clinical application.

Protective effects of Rubus tereticaulis leaves ethanol extract on rats with ulcerative colitis and bio-guided isolation of its active compounds: A combined in silico, in vitro and in vivo study

The aim of this study was to evaluate the therapeutic effect of active ethanol extract obtained from the leaves of Rubus tereticaulis (RTME) against colitis, and to purify major compounds from this extract by bioassay-directed isolation. Rats with colitis induced via intra-rectal acetic acid administration (5%, v/v) received RTME or sulfasalazine for three consecutive days. On day four, all rats were decapitated, and the colonic tissue samples were collected for macroscopic score, colon weight, reduced glutathione (GSH), myeloperoxidase (MPO), and malondialdehyde (MDA) analyses. The active compounds and chemical composition of RTME were determined by bio-guided isolation and LC-MS/MS, respectively. Compared to the colitis group, the rats treated with RTME displayed significantly lowered macroscopic scores and colon wet weights (p < 0.001). These effects were confirmed biochemically by a decrease in colonic MPO activity (p < 0.001), MDA levels (p < 0.001), and an increase in GSH levels (p < 0.001). Kaempferol-3-O-β-d-glucuronide (RT1) and quercetin-3-O-β-d-glucuronide (RT2) were found to be the major compounds of RTME, as evidenced by in vitro anti-inflammatory and antioxidant activity-guided isolation. Their anti-inflammatory/antioxidant activities were also predicted by docking simulations. Additionally, quinic acid, 5-caffeoylquinic acid, quercetin pentoside, quercetin glucoside, quercetin-3-O-β-d-glucuronide, kaempferol-3-O-β-d-glucuronide, and kaempferol rutinoside were identified in RTME via using LC-MS/MS. RT2, along with other compounds, may be responsible for the observed protective action of RTME against colitis. This study represents the first report on the beneficial effects of RTME in an experimental model of colitis and highlights the potential future use of RTME as a natural alternative to alleviate colitis.

A novel role of Nano selenium and sildenafil on streptozotocin-induced diabetic nephropathy in rats by modulation of inflammatory, oxidative, and apoptotic pathways

AIMS

The present study aimed to investigate the effect of nano selenium, sildenafil, and their combination on inflammation, oxidative stress, and apoptosis in streptozotocin-induced diabetic nephropathy in rats. Herein, a new anti-inflammatory pathway for sildenafil as a high-mobility group box (HMGB1) inhibitor was proposed using the molecular docking technique.

MATERIALS AND METHODS

Rats were divided into 7 groups: normal control, control nano selenium, control sildenafil, control diabetic, diabetic+ nano selenium, diabetic+ sildenafil, diabetic+ nano selenium+ sildenafil. The effects of drugs were evaluated by measuring serum urea, creatinine, lactate dehydrogenase (LDH), levels of tumor necrosis factor-alpha (TNF-α), Interleukin 1 beta (IL-1β), HMGB1, receptor advanced glycation end product (RAGE), malondialdehyde (MDA), thioredoxin reductase (TrxR) by biochemical assays, nuclear factor-kappa b (NF-κB), toll-like receptor (TLR4) by immunohistochemistry, gene expressions of caspase 3 and monocyte chemoattractant protein (MCP-1) besides histopathological investigations of renal cells.

KEY FINDINGS

Results showed beneficial effects of 8 weeks of treatment by nano selenium and sildenafil supported by improvement in kidney function, histopathological changes, and reduction in all of these parameters. These results supported molecular docking that indicated sildenafil had a high binding score and interactions with the HMGB1 receptor.

SIGNIFICANCE

The current study demonstrated a renoprotective effect of nano‑selenium and sildenafil by interfering at multiple pathways, especially the HMGB1/NF-κB signaling pathway.

Research progress of phosphodiesterase inhibitors in inflammatory bowel disease treatment

Inflammatory bowel disease is a recurrent chronic intestinal inflammatory disease with unknown etiology and no effective treatment. Phosphodiesterase (PDE) regulates a variety of physiological and pathophysiological processes by mediating the hydrolysis of intracellular second messengers cyclic adenosine monophosphate and cyclic guanosine monophosphate. In recent years, a series of researches suggest that PDE inhibitors such as several PDE4 inhibitors, PDE5 inhibitors (sildenafil, tadalafil and vardenafil), PDE3 inhibitors (cilostazol), PDE9 inhibitor (PF-04447943) and PDE3/PDE4 double inhibitor (pumafentrine) have ameliorating effect on experimental colitis in animals. In clinical trials, PDE4 inhibitor apremilast showed more therapeutic advantage than tetomilast. This article reviews the recent research progress of PDE inhibitors in treatment of inflammatory bowel disease.

Sildenafil beyond erectile dysfunction and pulmonary arterial hypertension: Thinking about new indications

Sildenafil, approved two decades ago, is the inhibitor of phosphodiesterase 5 (PDE5). First of all, it was designated for angina pectoris, but soon it showed a wonderful efficacy in erectile dysfunction (ED) and then pulmonary arterial hypertension (PAH). Due to the distribution of phosphodiesterase (PDE) in almost all organs, maybe it effects other diseases. Hence, a great number of investigations began to understand the role of PDEi in different organs. Preliminary research on sildenafil in cell culture and animal models has yielded promising results. Soon, a greater number of animal researches and clinical trials joined them. The results disclosed sildenafil can have beneficial effects in each organ such as heart, liver, kidney, brain, and intestines. Furthermore, it has significantly improved the prognosis of organ ischemia in various animal models. Clinical trials in several diseases, such as recurrent spontaneous miscarriage, fatty liver disease, bronchopulmonary dysplasia (BPD), heart failure, and premature ejaculation (PE) brought promising results. Although some clinical trials are available on the effects of sildenafil on various diseases, further studies on humans are needed to consolidate the ultimate effects of sildenafil. The aim of this review was to describe the effects of sildenafil on each organ and explain its mechanisms of action. Further, other PDE inhibitors such as tadalafil and vardenafil have been briefly discussed in parts of this review.

Effect of sildenafil on neuroinflammation and synaptic plasticity pathways in experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is a chronic immuno-inflammatory disease of the central nervous system characterized by demyelination and axonal damage. Cognitive changes are common in individuals with MS since inflammatory molecules secreted by microglia interfere with the physiological mechanisms of synaptic plasticity. According to previous data, inhibition of PDE5 promotes the accumulation of cGMP, which inhibits neuroinflammation and seems to improve synaptic plasticity and memory. The present study aimed to evaluate the effect of sildenafil on the signaling pathways of neuroinflammation and synaptic plasticity in experimental autoimmune encephalomyelitis (EAE). C57BL/6 mice were divided into three experimental groups (n = 10/group): (a) Control; (b) EAE; (c) EAE + sild (25 mg/kg/21 days). Sildenafil was able to delay the onset and attenuate the severity of the clinical symptoms of EAE. The drug also reduced the infiltration of CD4+ T lymphocytes and their respective IL-17 and TNF-α cytokines. Moreover, sildenafil reduced neuroinflammation in the hippocampus (assessed by the reduction of inflammatory markers IL-1β, pIKBα and pNFkB and reactive gliosis, as well as elevating the inhibitory cytokines TGF-β and IL-10). Moreover, sildenafil induced increased levels of NeuN, BDNF and pCREB, protein kinases (PKA, PKG, and pERK) and synaptophysin, and modulated the expression of the glutamate receptors AMPA and NMDA. The present findings demonstrated that sildenafil has therapeutic potential for cognitive deficit associated with multiple sclerosis.

Inhibitory effects of sildenafil and tadalafil on inflammation, oxidative stress and nitrosative stress in animal model of bronchial asthma

BACKGROUND

Cyclic neucleotides are involved in many cellular functions including smooth muscle relaxation, inflammation, and signal transduction. Sildenafil and tadalafil are phosphodiesterase-5 (PDE-5) inhibitors which prevent the degradation of cyclic neucleotide i.e. guanosine 3',5' cyclic monophosphate (cGMP) and increase the levels of cGMP. In this study sildenafil and tadalafil were evaluated for their anti-inflammatory, anti-oxidative and anti-nitrosative stress potential in animal model of bronchial asthma.

METHODS

Wistar rats were sensitized with 10 mg intraperitoneal (ip) ovalbumin adsorbed to 10 μg of aluminum hydroxide on day 0. Animals were given sildenafil (1 and 3 mg/kg ip) and tadalafil (1 and 3 mg/kg ip) from day 1 to day 14. Also, on day 14 animals were challenged with ovalbumin (1 mg ip). After 24 h, samples were collected to analyze interleukin-4 (IL-4) and tumour necrosis factor-α (TNF-α), in serum and bronchoalveolar lavage fluid (BALF). The oxidative stress markers malondialdehyde (MDA), reduced glutathione (GSH) and nitric oxide metabolites (NO_x) were also measured in serum.

RESULTS

Pre-treatment with sildenafil (1 and 3 mg/kg ip) and tadalafil (1 and 3 mg/kg ip) significantly reduced the levels of pro-inflammatory cytokines IL-4 and TNF-α in rat serum and BALF. In addition, pre-treatment with both the drugs decreased the levels of MDA and NO_x and increased the levels of GSH in serum.

CONCLUSIONS

Sildenafil and tadalafil decreased pro-inflammatory cytokines in serum and BALF. Both drugs inhibit oxidative and nitrosative stress in animal model of bronchial asthma and could have a therapeutic potential in bronchial asthma.

The TNBS-induced colitis animal model: An overview

Background

Despite recent advances the pathogenesis of Crohn's disease remains incompletely understood. A variety of animal models have been utilized in an effort to provide further insights and develop more therapeutic options. In order to simulate, to an extent, the pathogenesis and the clinical course of the disease, TNBS induced colitis is often used. Various approaches for inducing TNBS -colitis have been described in the literature.

Methods/results

In this review, we sought to present the animal model of TNBS induced colitis and outline the pathogenesis, pathophysiology, clinical course and pathological characteristics of the model. Furthermore, we describe the differences among those protocols regarding types of animals and colitis induction.

Data sources

The MEDLINE database was thoroughly searched using the keywords: TNBS, colitis, Crohn's disease, animal model. Two investigators independently reviewed the abstracts and appropriate articles were included in this review. Additional articles were gathered and evaluated.

Conclusion

The aim of this study was to thoroughly present an updated review of the TNBS-induced colitis protocols that are implemented by researchers.

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We sought to present the animal model of TNBS induced colitis and outline the pathogenesis, pathophysiology, clinical course and pathological characteristics of the model.

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Furthermore, we describe the differences among those protocols regarding types of animals and colitis induction.

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The MEDLINE database was thoroughly searched using the keywords: TNBS, colitis, Crohn's disease, animal model.

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Two investigators independently reviewed the abstracts and appropriate articles were included in this review.

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The aim of this study was to thoroughly present an updated review of the TNBS-induced colitis protocols that are implemented by researchers.

Antioxidant therapy for treatment of inflammatory bowel disease: Does it work?

Oxidative stress (OS) is considered as one of the etiologic factors involved in several signals and symptoms of inflammatory bowel diseases (IBD) that include diarrhea, toxic megacolon and abdominal pain. This systematic review discusses approaches, challenges and perspectives into the use of nontraditional antioxidant therapy on IBD, including natural and synthetic compounds in both human and animal models. One hundred and thirty four papers were identified, of which only four were evaluated in humans. Some of the challenges identified in this review can shed light on this fact: lack of standardization of OS biomarkers, absence of safety data and clinical trials for the chemicals and biological molecules, as well as the fact that most of the compounds were not repeatedly tested in several situations, including acute and chronic colitis. This review hopes to stimulate researchers to become more involved in this fruitful area, to warrant investigation of novel, alternative and efficacious antioxidant-based therapies.

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Major biomarkers used for evaluation of antioxidant therapy were MPO, TBARS/MDA and glutathione levels.

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Challenges were identified for the yet poor use of antioxidant therapy in IBD.

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This review stimulates the investigation of alternative and efficacious antioxidant therapies.

Carboxyamidotriazole: a novel inhibitor of both cAMP-phosphodiesterases and cGMP-phosphodiesterases

Carboxyamidotriazole (CAI) is a non-cytotoxic anti-tumor drug, which also shows considerable anti-inflammatory effects in a variety of animal models of inflammation. The exact target and mechanism of CAI were not clearly understood yet. In the present study, we demonstrate that CAI is a non-selective phosphodiesterase (PDE) inhibitor, which provides comprehensive inhibitions of both adenosine 3',5'-cyclic monophosphate specific PDE (cAMP-PDE) and guanosine 3',5'-cyclic monophosphate specific PDE (cGMP-PDE) isolated from rat brain, mouse pulmonary tissue, primary mouse peritoneal macrophages, RAW264.7 cells, Lewis lung carcinoma (LLC) cells and lymphocytic leukemia cells (L1210) with moderate potencies (IC50≈0.5-30μM). The comprehensive elimination of PDE activities in living LLC cells by CAI results in accumulation of intracellular cAMP and cGMP, which can be visualized by fluorescence resonance energy transfer (FRET)-based cyclic nucleotide sensors. The stimulation by 30μM CAI yielded ~1.5-fold greater cGMP responses compared with 10μM sildenafil citrate, whereas the influence of 30μM CAI on cAMP levels was similar as that of 100μM 3-isobutyl-1-methylxanthine (IBMX). The non-selective inhibitory effect of CAI on cAMP-PDE and cGMP-PDE increases the likelihood for CAI to affect the balance between the levels of intracellular cyclic nucleotides cAMP and cGMP, then a variety of cellular signaling pathways that regulate cell functions and even related disease processes. When examining the widely proven anti-tumor and anti-inflammatory activities of CAI, it is important to affirm its comprehensive inhibitory effect on PDEs, which makes it superior to some selective PDE inhibitors in a way.

Effectiveness of sildenafil and U-74389G in a rat model of colitis

BACKGROUND

Crohn disease is still incurable. Compounds with anti-inflammatory and/or antioxidative effects are tested in various preclinical models of the disease. Our aim was to investigate the effects of sildenafil and lazaroid U-74389G in an experimental rat model of trinitrobenzenesulfonic acid-induced colitis.

MATERIALS AND METHODS

Trinitrobenzenesulfonic acid was instilled into the colon of all male Wistar rats except for the rats belonging to the first group. For 6 days, the animals in group 3 were administered daily sildenafil orally, the rats in group 4 were administered daily U-74389G intravenously, and the rats in group 5 were coadministered daily sildenafil orally and intravenous U-74389G. The rats in groups 1 and 2 were not administered any treatment. During the study, the weights were recorded as a marker of clinical condition. The colon damage was evaluated using macroscopic colon mucosal damage index (CMDI), microscopic (Geboes score), and biochemical methods (tissue tumor necrosis factor [TNF]-α and malondialdehyde [MDA]).

RESULTS

Sildenafil reduced TNF-α tissue levels and increased body weight. U-74389G reduced TNF-α, the macroscopic index of mucosal damage score (CMDI) and increased body weight. The combined treatment with sildenafil and U-74389G reduced tissue levels of both TNF-α and MDA, lowered CMDI and microscopic Geboes score, and increased body weight.

CONCLUSIONS

U-74389G demonstrated a significant anti-inflammatory activity related to its ability to reduce colonic TNF-α, CMDI score, and improve weight change. We confirmed that sildenafil has anti-inflammatory capacity by reducing colonic TNF-α and by improving body weight. Finally, the combined treatment showed superior effects by reducing colonic TNF-α, colonic MDA, CMDI score, Geboes score, and by improving weight.

A review on chemical-induced inflammatory bowel disease models in rodents

Ulcerative colitis and Crohn's disease are a set of chronic, idiopathic, immunological and relapsing inflammatory disorders of the gastrointestinal tract referred to as inflammatory bowel disorder (IBD). Although the etiological factors involved in the perpetuation of IBD remain uncertain, development of various animal models provides new insights to unveil the onset and the progression of IBD. Various chemical-induced colitis models are widely used on laboratory scale. Furthermore, these models closely mimic morphological, histopathological and symptomatical features of human IBD. Among the chemical-induced colitis models, trinitrobenzene sulfonic acid (TNBS)-induced colitis, oxazolone induced-colitis and dextran sulphate sodium (DSS)-induced colitis models are most widely used. TNBS elicits Th-1 driven immune response, whereas oxazolone predominantly exhibits immune response of Th-2 phenotype. DSS-induced colitis model also induces changes in Th-1/Th-2 cytokine profile. The present review discusses the methodology and rationale of using various chemical-induced colitis models for evaluating the pathogenesis of IBD.

Nadroparin sodium activates Nrf2/HO-1 pathway in acetic acid-induced colitis in rats

Effects of nadroparin sodium, a low molecular weight heparin, in colitis was investigated by analyzing proteins implicated in nuclear factor E2-related factor-2/heme oxygenase-1 (Nrf2/HO-1) and nuclear factor kappa B (NF-κB) pathways. Twenty-eight rats were used. Colitis was induced by acetic acid (AA). Nadroparin sodium was given to prevention and treatment groups in addition to AA. Colitis was assessed histologically and levels of proteins were analyzed with Western blot. Nadroparin not only prevented and ameliorated the AA-induced colitis histopathologically but also decreased expression of colon NF-κB, activator protein-1, cyclooxygenase-2, tumor necrosis factor-alpha, and IL-6, which were significantly increased in group AA compared to control. The accumulation of Nrf2 in nuclear fraction and HO-1 found low in group AA was increased with nadroparin (p < 0.05). The mean malondialdehyde level increased with AA and was decreased significantly with nadroparin prevention and treatment (p < 0.001). Nadroparin sodium has both protective and therapeutic effects against colonic inflammation via exerting anti-oxidative and anti-inflammatory effects by modulating Nrf2/HO-1 and NF-κB pathways.

Sildenafil attenuates TNBS-induced colitis in rats: possible involvement of cGMP and KATP channels

The involvement of cGMP/KATP pathway in effects of sildenafil on experimental colitis was investigated. Sildenafil significantly attenuated colonic injury markers. These effects were reversed by the addition of glibenclamide or ODQ, indicating the involvement of ATP-sensitive potassium channels (KATP) and cGMP, respectively.

Phosphodiesterase inhibitors in inflammatory bowel disease

Inflammatory bowel disease (IBD) is fundamentally a relapsing and remitting disease appearing in forms of ulcerative colitis (UC) or Crohn's disease (CD) with a non-well-known etiology. With the hope to prevent adverse drug events and to increase the efficacy of therapies for IBD, in the recent years, other than new monoclonal antibodies such as infliximab, the novel phosphodiesterase inhibitors (PDEIs) have been introduced. Among PDE4Is, rolipram, OPC-6535, mesopram, roflumilast and tetomilast have shown beneficial effects in experimental colitis. Unfortunately until now, human studies have not been successful in showing significant superiority of PDE4Is in the treatment of IBD. Parallel with discovery of PDE4Is and their anti-inflammatory properties, inhibiting other PDE isoenzymes in immune and proinflammatory cells is on the way. PDE7Is have shown synergistic effect with PDE4Is and they may act similar to PDE3Is in experimental settings. Sildenafil as the PDE5I has shown good effects in experimental colitis by balancing oxidant-antioxidant status. Although the present data about PDE superfamily and their specific roles in gastrointestinal tract is limited but inhibitors of PDE4, PDE5 and PDE7 seem good candidates as the next generation of effective drugs. The synergistic anti-inflammatory effect of PDE4Is and PDE7Is is also important.

The effect of phosphodiesterase-5 inhibition by sildenafil citrate on inflammation and apoptosis in rat experimental colitis

AIMS

To investigate the effect of sildenafil citrate (SIL) on the extent of tissue integrity, oxidant-antioxidant status and apoptosis in rats with colitis.

MAIN METHODS

Colitis was induced by trinitrobenzenesulphonic acid (TNBS) in 40% ethanol (30 mg/ml; 0.8 ml) given intrarectally to Sprague-Dawley rats. Sildenafil (25 mg/kg/day) was administered after the induction of colitis and the treatment was continued for 7 days. Other groups received subcutaneously either N(G)-nitro- L-arginine methyl ester (l-NAME; 25 mg/kg) or N(G)-nitro-d-arginine methyl ester (d-NAME; 25 mg/kg) before SIL. After decapitation, the distal colon was scored and stored for the measurement of malondialdehyde (MDA) level, glutathione (GSH) content, myeloperoxidase (MPO) activity and apoptosis. Oxidant generation was monitored by using chemiluminescence (CL). Blood was collected for tumor necrosis factor (TNF)-α and interleukin (IL)-10 assays.

KEY FINDINGS

The macroscopic lesion score of the colitis group was reduced by SIL (p < 0.01) and this effect was abolished by l-NAME (p < 0.01). Increase in colonic MDA along with a concomitant decrease in GSH of the colitis group was reversed by SIL (p < 0.01 and p < 0.001, respectively). l-NAME prevented the effect of SIL on GSH content (p < 0.001). Sildenafil also reduced the elevated MPO of the colitis group (p < 0.001) and this effect was reversed by L-NAME (p < 0.01). Increase in lucigenin CL and serum TNF-α levels in the colitis group were also prevented by SIL (p < 0.001 and p < 0.01, respectively).

SIGNIFICANCE

Sildenafil is beneficial in TNBS-induced rat colitis partially by nitric oxide-dependent mechanisms via the maintenance of oxidant-antioxidant status, prevention of apoptosis, superoxide production and cytokine release.

The effect of methylsulfonylmethane on the experimental colitis in the rat

Methylsulfonylmethane (MSM), naturally occurring in green plants, fruits and vegetables, has been shown to exert anti-inflammatory and antioxidant effects. MSM is an organosulfur compound and a normal oxidative metabolite of dimethyl sulfoxide. This study was carried out to investigate the effect of MSM in a rat model of experimental colitis. Colitis was induced by intracolonic instillation of 1 ml of 5% of acetic acid. Rats were treated with MSM (400 mg/kg/day, orally) for 4 days. Animals were euthanized and distal colon evaluated histologically and biochemically. Tissue samples were used to measurement of malondialdehyde (MDA), myeloperoxidase (MPO), catalase (CAT), glutathione (GSH) and proinflammatory cytokine (TNF-α and IL-1β) levels. Results showed that MSM decreased macroscopic and microscopic colonic damage scores caused by administration of acetic acid. MSM treatment also significantly reduced colonic levels of MDA, MPO and IL-1β, while increased the levels of GSH and CAT compared with acetic acid-induced colitis group. It seems that MSM as a natural product may have a protective effect in an experimental ulcerative colitis.