Oral methylmercury intoxication aggravates cardiovascular risk factors and accelerates atherosclerosis lesion development in ApoE knockout and C57BL/6 mice

Methylmercury (MeHg) intoxication is associated with hypertension, hypercholesterolemia, and atherosclerosis by mechanisms that are not yet fully understood. We investigated the effects of MeHg intoxication in atherosclerosis-prone (ApoE-KO) and resistant C57BL/6 mice. Mice were submitted to carotid stenosis surgery (to induce atherosclerosis faster) and received water or MeHg solution (20 mg/L) for 15 days. Tail plethysmography was performed before and after MeHg exposure. Food and MeHg solution intakes were monitored weekly. On the 15th day, mice were submitted to intravital fluorescence microscopy of mesenteric vasculature to observe in vivo leukocyte rolling and adhesion. Results showed that despite the high hair and liver Hg concentrations in the MeHg group, food and water (or MeHg solution) consumption and liver function marker levels were similar to those in controls. MeHg exposure increased total cholesterol, the atherogenic (non-HDL) fraction and systolic and diastolic blood pressure. MeHg exposure also induced inflammation, as seen by the increased rolling and adhered leukocytes in the mesenteric vasculature. Atherosclerosis lesions were more extensive in the aorta and carotid sites of MeHg-ApoE knockout mice. Surprisingly, MeHg exposure also induced atherosclerosis lesions in C57BL/6 mice, which are resistant to atherosclerosis formation. We concluded that MeHg intoxication might represent a risk for cardiovascular diseases since it accelerates atherogenesis by exacerbating several independent risk factors.

L-arginine pretreatment reduces intestinal mucositis as induced by 5-FU in mice

Beneficial effects of L-arginine on immune responses and bowel function have been reported. Mucositis is a side effect of chemotherapy treatment that affects approximately 40% of patients. This complication is characterized by inflammation that affects the gastrointestinal tract, increasing permeability and causing abdominal pain, nausea, vomiting, and diarrhea, which worsen the patient's nutritional status and increases morbimortality. The aim of this study was to evaluate the effect of pretreating with 2% L-arginine supplementation in water on mucositis as induced by 5-fluorouracil (5-FU; a single dose of 200 mg/kg body weight) in Swiss male mice. The effect of L-arginine on weight, intestinal permeability, morphology, and the histopathological score of the small intestine (from 0 to 12), oxidative stress, myeloperoxidase (MPO), and N-acetylglucosaminidase (NAG) activities were evaluated. Intestinal length improvement was observed, in addition to the partial recovery of the mucosal architecture. L-arginine attenuated the histopathological score and MPO activity. There was also an improvement in intestinal permeability, despite weight loss after 5-FU administration. In conclusion, L-arginine can positively impact intestinal mucositis by promoting partial mucosal recovery, reducing inflammation and improving intestinal permeability.