Neurogenesis within the hippocampus after chronic methylphenidate exposure.

Methylphenidate is a psychostimulant used to treat attention deficit hyperactivity disorder. Neurogenesis occurs throughout adulthood within the dentate gyrus of the hippocampus and can be altered by psychoactive medications; however, the impact of methylphenidate on neurogenesis is not fully understood. We investigated the effects of chronic low (1 mg/kg) and high (10 mg/kg) intraperitoneal doses of methylphenidate on neurogenesis in mouse hippocampus following 28 days and 56 days of treatment. Interestingly, methylphenidate, at both doses, increased neurogenesis. However, if methylphenidate treatment was not continued, the newly generated cells did not survive after 28 days. If treatment was continued, the newly generated neurons survived only in the mice receiving low-dose methylphenidate. To investigate the mechanism for this effect, we examined levels of proteins linked to cell proliferation in the hippocampus, including brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), vascular endothelial growth factor (VEGF), tropomyosin receptor kinase B (TrkB), and beta-catenin. BDNF or GDNF levels were not significantly different between groups. However, hippocampal VEGF, TrkB, and beta-catenin were significantly increased in mice receiving low-dose methylphenidate for 28 days compared to controls. Interestingly, high-dose methylphenidate significantly decreased beta-catenin after 28 days and decreased VEGF, beta-catenin, and TrkB after 56 days compared to controls. Thus, low-dose methylphenidate appears to increase cell proliferation and cell survival in the hippocampus, and these effects may be mediated by increase in VEGF, TrkB, and beta-catenin. While high dose methylphenidate may initially increase neuronal proliferation, newly generated neurons are unable to survive long-term, possibly due to decrease in VEGF, TrkB and beta-catenin.

Exacerbation of celecoxib-induced renal injury by concomitant administration of misoprostol in rats.

Nonsteroidal anti-inflammatory drugs (NSAIDs) can produce adverse effects by inhibiting prostaglandin (PG) synthesis. A PGE1 analogue, misoprostol, is often utilized to alleviate NSAID-related gastrointestinal side effects. This study examined the effect of misoprostol on celecoxib renal toxicity. Additionally, the effects of these drugs on cardiovascular parameters were evaluated. Four randomized rat groups were orally gavaged for 9 days, two groups receiving vehicle and two groups receiving misoprostol (100 µg/kg) twice daily. Celecoxib (40 mg/kg) was co-administered once daily to one vehicle and one misoprostol group from days 3 to 9. Urine and blood samples were collected and blood pressure parameters were measured during the study period. Hearts and kidneys were harvested on final day. Day 2 urinary electrolyte samples revealed significant reductions in sodium excretion in misoprostol (0.12 ± 0.05 µmol/min/100 g) and misoprostol+celecoxib groups (0.07 ± 0.02 µmol/min/100 g). At day 3, all treatment groups showed significantly reduced sodium excretion. Potassium excretion diminished significantly in vehicle+celecoxib and misoprostol+celecoxib groups from day 3 onward. Urinary kidney injury molecule-1 levels were significantly increased in vehicle+celecoxib (0.65 ± 0.02 vs. 0.35 ± 0.07 ng/mL, p = 0.0002) and misoprostol+celecoxib (0.61 ± 0.06 vs. 0.37 ± 0.06 ng/mL, p = 0.0015) groups when compared to baseline; while plasma levels of cardiac troponin I increased significantly in vehicle+celecoxib (p = 0.0040) and misoprostol+misoprostol (p = 0.0078) groups when compared to vehicle+vehicle. Blood pressure parameters increased significantly in all misoprostol treated groups. Significant elevation in diastolic (p = 0.0071) and mean blood pressure (p = 0.0153) was noted in misoprostol+celecoxib compared to vehicle+celecoxib. All treatments produced significant tubular dilatation/necrosis compared to control. No significant myocardial changes were noticed; however, three animals presented with pericarditis. Kidney, heart, and plasma celecoxib levels revealed no significant change between vehicle+celecoxib and misoprostol+celecoxib. Concomitant misoprostol administration did not prevent celecoxib renal toxicity, and instead exacerbated renal side effects. Misoprostol did not alter plasma or tissue celecoxib concentrations suggesting no pharmacokinetic interaction between celecoxib and misoprostol.

Effects of rebamipide on nephrotoxicity associated with selected NSAIDs in rats.

Use of nonsteroidal anti-inflammatory drugs (NSAIDs) is primarily limited by renal and gastrointestinal adverse effects. Rebamipide suppresses gastric mucosal injury when administered with NSAIDs. This study aimed to determine rebamipide's influence upon renal effects following concomitant use with celecoxib or diclofenac. On day 0, rats were randomly divided into 6 groups (n≥6). On days 1 and 2, three groups received placebo and three groups were administered rebamipide (30 mg/kg) twice daily. On day 3, the rats treated with placebo received another dose of placebo and ten minutes later a single dose of celecoxib (40 mg/kg), diclofenac (10mg/kg), or placebo, respectively. The rats treated with rebamipide received one more dose of rebamipide and ten minutes later one single dose of celecoxib, diclofenac, or placebo, respectively. Urine and blood samples were collected on days 0, 2, and 3. Sodium and potassium excretion rates decreased significantly in the rats treated with celecoxib, diclofenac, rebamipide plus celecoxib, or rebamipide plus diclofenac on day 3. Blood urea nitrogen (BUN) levels significantly increased in placebo plus diclofenac and rebamipide plus diclofenac groups on day 3. Comparing the two groups, the levels of BUN was significantly higher in the rebamipide plus diclofenac group compared to that of placebo plus diclofenac group. Concomitant administration of rebamipide with either NSAID caused a rise in concentrations of urinary kidney injury molecule-1. Histopathological evaluations revealed an intensified NSAID-induced tubular necrosis by rebamipide. Based upon the results obtained, concomitant administration of rebamipide with NSAIDs enhances the effect of NSAIDs on tubular injury.