Attenuation of the levels of pro-inflammatory cytokines prevents depressive-like behavior during ethanol withdrawal in mice.

Clinical studies indicate that alcohol-dependent patients may develop depressive symptoms during abstinence, which may increase the likelihood of relapse. It is known that both in alcohol exposure and depression, there is an increase in the levels of pro-inflammatory cytokines in the brain. However, the putative contribution of increased levels of pro-inflammatory cytokines in the development of depressive-like behavior during ethanol withdrawal has not been evaluated. In the present study, we aimed to investigate if ethanol withdrawal-induced depressive-like behavior is related to increased levels of pro-inflammatory cytokines in the brain. Male mice were treated with vehicle (saline 0.9%, v.o.) or ethanol (2 g/kg, v.o.) for 14 days. After 5 days of cessation of the ethanol treatment, mice were subjected to the forced swim test (FST), tail suspension test (TST), and open field test (OFT) and then sacrificed. Their brains were analyzed for the levels of pro-inflammatory cytokines. Ethanol withdrawal mice showed increased immobility time in the FST and TST than by the control group, indicating increased depressive-like behavior. No alterations in OFT were observed. Ethanol withdrawal increased the levels of tumor necrosis factor-alpha (TNF-α) in the hippocampus and striatum, interleukin-1 beta (IL-1ß) in the hippocampus, and IL-6 in the prefrontal cortex and hippocampus. Treatment of mice with nimesulide (5 or 10 mg/kg/day), a cyclooxygenase-2 inhibitor, during ethanol withdrawal prevented the increase in immobility time in the TST. Similar results were observed in the FST upon nimesulide treatment, although with a higher dose. Nimesulide treatment (10 mg/kg) prevented the ethanol withdrawal-induced alterations in the levels of TNF-α, IL-1ß, and IL-6 in the hippocampus, prefrontal cortex, and striatum. Treatment of mice with an atypical antidepressant drug, vilazodone (0.3 or 1 mg/kg) prevented the increase in depressive-like behavior induced by ethanol withdrawal in the TST. In the FST, the increase in immobility time was prevented only by 1 mg/kg vilazodone treatment. Vilazodone prevented the increase in the levels of TNF-α, IL-1ß, and IL-6 in the hippocampus, IL-6 in the prefrontal cortex, and TNF-α in the striatum. In conclusion, these data indicate that increased levels of pro-inflammatory cytokines may play a role in the development of depressive-like behavior during ethanol withdrawal in mice.

Neuroprotective effect of melatonin against lipopolysaccharide-induced depressive-like behavior in mice.

Accumulating evidence indicates an interaction between inflammation and depression since increased levels of pro-inflammatory cytokines are associated with depression-related symptoms. Melatonin is a hormone synthesized and secreted by the pineal gland with antioxidant, anti-inflammatory and antidepressant-like effects. In this way, it would be interesting to evaluate the putative antidepressant-like effect of melatonin treatment in an acute inflammation mice model of depression. The present study aimed to investigate the effect of melatonin treatment on lipopolysaccharide (LPS) induced depressive-like behavior, neuroinflammation, oxidative stress and alteration on brain-derived neurotrophic fator (BDNF) levels. Mice were treated with melatonin (10 mg/kg, i.p.) 30 min before LPS (0.5 mg/kg, i.p.) injection. Twenty-four hours after LPS infusion, mice were submitted to the behavioral tests and, thereafter, biochemical determinations were performed. Melatonin treatment prevented LPS-induced depressive-like behavior in the forced swim and tail suspension tests with no alterations in locomotor activity evaluated in the open field test. Melatonin attenuated LPS-induced increase in tumor necrosis factor-α (TNF-α) and reduction of BDNF levels in the hippocampus. Treatment with melatonin also prevented LPS-induced increase in lipid peroxidation and the reduction of glutathione levels in the hippocampus. In conclusion, the present study suggests that melatonin treatment exerted neuroprotective effects against LPS-induced depressive-like behavior which may be related to reduction of TNF-α release, oxidative stress and modulation of BDNF expression.