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

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.

The effect of montelukast, a leukotriene receptor antagonist, on the acetic acid-induced model of colitis in rats: Involvement of NO-cGMP-KATP channels pathway

Inflammatory bowel disease is a chronic autoimmune disorder that may involve entire gastrointestinal tract. The leukotrienes have a role as mediators in the pathophysiology of colitis. Here, we investigated the effect of a leukotriene receptor antagonist, montelukast, and also the role of the NO-cGMP-K_ATP channel pathway in acetic acid-induced colitis. Rectal administration of acetic acid (4%) was used for induction of colitis in rats. To investigate our hypothesis, the rats were intraperitoneally pre-treated with L-NAME (NOS inhibitor), L-arginine, sildenafil, methylene blue, glibenclamide, or diazoxide 15 min before treatment with montelukast (5-20 mg/kg, i. p.), for three consecutive days. Then, microscopic, macroscopic, and inflammatory parameters were evaluated. Montelukast reduced the microscopic and macroscopic damage induced by acetic acid. Montelukast also reduced the level of IL-1β and TNF-α. We also showed that the effects of montelukast were significantly attenuated by L-NAME, methylene blue (guanylate cyclase inhibitor), and an ATP-sensitive potassium channel blocker (glibenclamide). Also, the administration of L-arginine, sildenafil, and diazoxide before montelukast produced protective effect. In conclusion, the pathway of the NO-cGMP-KATP channel is involved in the protective effect of montelukast in acetic acid-induced colonic tissue damage.

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.

The pro-inflammatory cytokine TNF-α inhibits lymphatic pumping via activation of the NF-κB-iNOS signaling pathway

OBJECTIVE

Mesenteric lymphatic vessel pumping, important to propel lymph and immune cells from the intestinal interstitium to the mesenteric lymph nodes, is compromised during intestinal inflammation. The objective of this study was to test the hypothesis that the pro-inflammatory cytokine TNF-α, is a significant contributor to the inflammation-induced lymphatic contractile dysfunction, and to determine its mode of action.

METHODS

Contractile parameters were obtained from isolated rat mesenteric lymphatic vessels mounted on a pressure myograph after 24-hours incubation with or without TNF-α. Various inhibitors were administered, and quantitative real-time PCR, Western blotting, and immunofluorescence confocal imaging were applied to characterize the mechanisms involved in TNF-α actions.

RESULTS

Vessel contraction frequency was significantly decreased after TNF-α treatment and could be restored by selective inhibition of NF-кB, iNOS, guanylate cyclase, and ATP-sensitive K⁺ channels. We further demonstrated that NF-кB inhibition also suppressed the significant increase in iNOS mRNA observed in TNF-α-treated lymphatic vessels and that TNF-α treatment favored the nuclear translocation of the p65 NF-κB subunit.

CONCLUSIONS

These findings suggest that TNF-α decreases mesenteric lymphatic contractility by activating the NF-κB-iNOS signaling pathway. This mechanism could contribute to the alteration of lymphatic pumping reported in intestinal inflammation.

Role of epithelial ion transports in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic inflammatory disorder with a complex pathogenesis. Diarrhea is a highly prevalent and often debilitating symptom of IBD patients that results, at least in part, from an intestinal hydroelectrolytic imbalance. Evidence suggests that reduced electrolyte absorption is more relevant than increased secretion to this disequilibrium. This systematic review analyses and integrates the current evidence on the roles of epithelial Na(+)-K(+)-ATPase (NKA), Na(+)/H(+) exchangers (NHEs), epithelial Na(+) channels (ENaC), and K(+) channels (KC) in IBD-associated diarrhea. NKA is the key driving force of the transepithelial ionic transport and its activity is decreased in IBD. In addition, the downregulation of apical NHE and ENaC and the upregulation of apical large-conductance KC all contribute to the IBD-associated diarrhea by lowering sodium absorption and/or increasing potassium secretion.

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.