Background: Methotrexate treatment has been associated to intestinal epithelial damage. Studies have suggested an important role of nitric oxide in such injury. The aim of this study was to investigate the role of nitric oxide (NO), specifically iNOS on the pathogenesis of methotrexate (MTX)-induced intestinal mucositis.Methods: Intestinal mucositis was carried out by three subcutaneous MTX injections (2.5 mg/kg) in Wistar rats and in inducible nitric oxide synthase knock-out (iNOS^-/-) and wild-type (iNOS^+/+) mice. Rats were treated intraperitoneally with the NOS inhibitors aminoguanidine (AG; 10 mg/Kg) or L-NAME (20 mg/Kg), one hour before MTX injection and daily until sacrifice, on the fifth day. The jejunum was harvested to investigate the expression of Ki67, iNOS and nitrotyrosine by immunohistochemistry and cell death by TUNEL. The neutrophil activity by myeloperoxidase (MPO) assay was performed in the three small intestine segments.Results: AG and L-NAME significantly reduced villus and crypt damages, inflammatory alterations, cell death, MPO activity, and nitrotyrosine immunostaining due to MTX challenge. The treatment with AG, but not L-NAME, prevented the inhibitory effect of MTX on cell proliferation. MTX induced increased expression of iNOS detected by immunohistochemistry. MTX did not cause significant inflammation in the iNOS^-/-mice.Conclusion: These results suggest an important role of NO, via activation of iNOS, in the pathogenesis of intestinal mucositis.

The irinotecan (CPT-11) causes intestinal mucositis and diarrhea that may be related to changes in the enteric nervous system (ENS). In inflammatory condition, mast cells release a variety of pro-inflammatory mediators that can interact with the ENS cells. It has not been explored whether CPT-11 is able to alter the enteric glial and neuronal cell, and the role of mast cells in this effect. Therefore, this study was conducted to investigate the effect of CPT-11 on the enteric glial and neuronal cells, as well as to study the role of mast cells in the CPT-11-induced intestinal mucositis. Intestinal mucositis was induced in Swiss mice by the injection of CPT-11 (60 mg/kg, i.p.) once a day for 4 days following by euthanasia on the fifth day. To investigate the role of mast cells, the mice were pretreated with compound 48/80 for 4 days (first day, 0.6 mg/kg; second day, 1.0 mg/kg; third day, 1.2 mg/kg; fourth day, 2.4 mg/kg) to induce mast cell degranulation before the CPT-11 treatment. Here, we show that CPT-11 increased glial fibrillary acidic protein (GFAP) and S100β gene and S100β protein expressions and decreased HuC/D protein expression in the small intestine segments. Concomitantly, CPT-11 enhanced tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) levels and inducible nitric oxide synthase (iNOS) gene expression, associated with an increase in the total number macrophages (positive cells for ionized calcium-binding adapter molecule, Iba-1) and degranulated mast cells in the small intestine segments and caused significant weight loss. The pretreatment with compound 48/80, an inductor of mast cells degranulation, significantly prevented these CPT-11-induced effects. Our data suggests the participation of mast cells on the CPT-11-induced intestinal mucositis, macrophages activation, enteric reactive gliosis, and neuron loss.

The development of the gastric lesion is complex and the result of the imbalance between aggressive and protective factors, involving the generation of free radicals and disturbance in nitric oxide (NO) production. Sulphated polysaccharides (SP), from marine algae, are widely used in biotechnological and pharmaceutical areas. In this study, we evaluated the effects of SP from the green marine alga Caulerpa mexicana (Cm-SP) in ethanol-induced gastric damage models in mice. Cm-SP (2, 20, or 200 mg/kg), administered p.o., significantly reduced gastric damage, and these effects were inhibited through pretreatment with indomethacin. Cm-SP (200 mg/kg) prevented the ethanol-induced decline in glutathione and restored its normal level. Moreover, it was able to normalize the elevated thiobarbituric acid reactive substance levels. However, Cm-SP did not show any significant effects on NO₂/NO₃ level, when compared to the ethanol group. The pretreatment with L- NAME induced gastric mucosal damage and did not inhibit the gastroprotective effect of Cm-SP (200 mg/kg). In conclusion, the gastroprotective effects of Cm-SP in mice involve prostaglandins and reduction in the oxidative stress and are independent of NO.

Peptic ulcer (PU) occurs as acute or chronic inflammation of the stomach and/or duodenum. It is characterized by oxidative stress, intense inflammation, and hemorrhage, which result from an imbalance between the defensive and harmful factors. Cecropia pachystachya (CP) contains flavonoids, terpenes, and polyphenols such as chlorogenic acid, which is known for its antioxidant properties. This study aimed to investigate the antiulcerogenic activities and properties of the CP leaf extract on naproxen (NPX)-induced gastric ulcers. MTT assay was used to evaluate CP cytotoxicity on intestinal epithelial cells (IEC-6). Gastric ulcer was induced in male Swiss mice by pretreating them with 0.5% carboxymethylcellulose (CMC, a vehicle control) or CP (3, 10, and 30 mg/kg reconstituted in 0.5% CMC) for 30 min, followed by administration of NPX (300 mg/kg) and then euthanization after 6 h. The stomach segments were collected for macroscopia, microscopia, glutathione (GSH), malondialdehyde (MDA), myeloperoxidase (MPO, a neutrophil infiltration marker), nitrite/nitrate, interleukin (IL)-6, and tumor necrosis factor (TNF)-α analysis. CP extract did not affect IEC viability. CP extract (1, 3, and 10 mg/kg) reduced (p < 0.05) NPX-induced macroscopic and microscopic gastric lesions. In addition, it (3.0 mg/kg) prevented the depletion of GSH levels and reduced MDA formation and MPO. TNF-α and IL-6 levels were also reduced in mice subjected to NPX-induced gastric ulcers, compared with the control group. Furthermore, the extract reversed the increase in nitrite/nitrate concentration induced by NPX in stomach tissues. Therefore, our results demonstrate that CP has anti-inflammatory and antioxidant activities against NPX-induced gastric ulcers.