Agomelatine attenuates cisplatin-induced cognitive impairment via modulation of BDNF/TrkB signaling in rat hippocampus

Cisplatin is a drug used effectively in the treatment of malignant tumors. However, cisplatin has many side effects, including cognitive impairment. Agomelatine, a synthetic melatonin analogue, is an important antidepressant. Increasing evidence has shown that agomelatine may be a potential neuroprotective agent. The aim of this study was to investigate the effect of agomelatine on learning and memory functions in cisplatin-induced cognitive impairment in a rat model. Male rats were administered agomelatine and cisplatin for 4 weeks. Neurobehavioral tests were performed at the end of the 4th week. After behavioral tests, rats were euthanized and BDNF, TNF, IL-1β, MDA and GSH levels were measured in hippocampal homegenates by ELISA. In addition, nNOS and TrkB receptor activity were measured immunohistochemically. The results showed that agomelatine significantly improved cognitive functions in spatial memory tests in rats with cisplatin-induced cognitive impairment. In addition, agomelatine treatment positively affected the discrimination index (DI). On the other hand, agomelatine treatment elevated cisplatin-suppressed hippocampal BDNF levels. Agomelatine treatment reduced cisplatin-induced neuroinflammation by suppressing TNF and IL-1β levels. Similarly, agomelatine reduced oxidative stress in the hippocampus. Histological findings showed that agomelatine treatment reduced pyramidal neuron damage in hippocampal DG, CA1 and CA3. Cisplatin increased nNOS and TrkB positivity in DG, CA1 and CA3 neurons compared to control. In contrast, agomelatine treatment decreased both nNOS and TrkB positive scores. These findings indicate that agomelatine reduces cisplatin-related cognitive impairment by exerting anti-inflammatory action and possibly by the modulation of the BDNF/TrkB/nNOS pathways in the hippocampus.

The effects of dexmedetomidine on early acute kidney injury in severely burned rats

OBJECTIVE

Burns are a global medical and economic problem. In addition to high costs, the lengthy therapeutic process and the emotional trauma experienced by patients and their families indirectly worsen the socioeconomic damage caused. Kidney failure observed after burns is highly correlated with mortality.

MATERIALS AND METHODS

Twenty-eight male Sprague-Dawley rats (age four months, weight 250-350 g) were included in the study. They were randomly assigned into four groups consisting of seven rats each with similar mean weights. Group 1 (n=7) represented the healthy control group (C), Group 2 (n=7) the Sham+dexmedetomidine (DEX) 100 mcg/kg (three doses) (S+DEX100) group, Group 3 (n=7) the 30% Burn (B), and Group 4 (n=7) the 30% Burn+DEX 100 mcg/kg/day group (B+DEX100) (three doses). Thiobarbituric acid reactive substances (TBARS), total thiol (TT), interleukin-1 (IL-1) and tumor necrosis factor-α (TNF-α) values in kidney tissues were investigated biochemically, and histopathological analyses were also performed. Nuclear factor κB (NF-κB)/p65 was measured using immunohistochemistry, and the TUNEL assay was applied to indicate apoptotic tubular epithelial cells.

RESULTS

TBARS, IL-1, and TNF-α in kidney tissues decreased in the B+DEX100 group compared to the 30% burn group, while total thiol values increased. Histopathologically, atypical glomeruli, particularly necrotic tubules, and inflammation in peritubular areas decreased in the B+DEX100 group compared to the 30% burn group. In addition, apoptotic tubular epithelial cells exhibiting TUNEL positivity and tubular epithelial cells exhibiting NF-кβ/p65 positivity also decreased in the B+DEX100 group compared to the 30% burn group.

CONCLUSIONS

Dexmedetomidine reduced apoptotic activity in rats and exhibited anti-inflammatory antioxidant effects in the burn model in this study.

Bee pollen increases hippocampal brain-derived neurotrophic factor and suppresses neuroinflammation in adult rats with chronic immobilization stress

Chronic stress is a potential problem associated with anxiety, depression, and cognitive dysfunction. Bee pollen, a powerful antioxidant, has many therapeutic effects. In this study, we aimed to examine the effects of one of the Anatolian bee pollens on depression/anxiety. 24 male Sprague Dawley rats were divided into 3 groups as control, stress, and bee pollen + stress. Bee pollen (200 mg/kg/day) was given to rats exposed to physical stress for 10 days. Open field test (OFT) and forced swimming test (FST) were applied to monitor the behavioral changes of the rats. After behavioral tests, the rats were euthanized. Brain-derived neurotrophic factor (BDNF), interleukin 1 beta (IL-1β), and tumor necrosis factor-alpha (TNF-α) levels were measured by ELISA to evaluate neurological and biochemical changes in rat hippocampal tissue. In addition, malondialdehyde (MDA) and glutathione (GSH) levels in the brain were evaluated. According to the behavioral test results, bee pollen reduced anxiety-like behavior but did not affect depression-like behavior. We also found that bee pollen suppressed neuroinflammation while reducing oxidative stress and lipid peroxidation in hippocampal tissues. Moreover, bee pollen significantly increased the level of BDNF in the hippocampus. In conclusion, bee pollen reduced oxidative damage and neuroinflammation caused by immobilization stress in rat brain tissue. Therefore, we suggest that bee pollen may be an effective natural compound in alleviating the negative effects caused by immobilization stress.

Apelin-13 activates the hippocampal BDNF/TrkB signaling pathway and suppresses neuroinflammation in male rats with cisplatin-induced cognitive dysfunction

It has been established that cisplatin causes neuronal damage and cognitive impairment. However, the mechanism is not sufficiently clear. Apelin-13 is an endogenous peptide with strong neuroprotective effects through the synthesis of neurotrophic factors and suppression of inflammation. The aim of this study was to investigate the role of brain-derived neurotrophic factor/tropomyosin receptor kinase B (BDNF/TrkB) signaling pathway and the potential inhibitory effects of apelin-13 in the mechanism of cisplatin-induced hippocampal damage and cognitive impairment. Apelin-13 was administered to adult sprague dawley male rats at a dose of 20 nmol/kg every day for 4 weeks, cisplatin was administered at a dose of 5 mg/kg once a week for 4 weeks. The spatial and recognition memory tests of the rats were performed on the 5th week. BDNF and the inflammatory cytokines tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) levels were measured by ELISA in hippocampal homogenates. Pyramidal neuron and glial cell damage in the hippocampal CA1, CA3 and dentate gyrus (DG) were analyzed histologically. TrkB activity in the hippocampus was determined by immunohistochemical methods. Cisplatin impaired spatial and recognition memory in rats, while apelin-13 improved spatial memory but did not affect recognition memory. Cisplatin suppressed BDNF in the hippocampus while increased IL-1β and TNF-α. In contrast, apelin-13 administration increased BDNF but significantly suppressed TNF-α and IL-1B. Cisplatin caused pyramidal neuron and glial cell damage in CA1, CA3 and DG. In the cisplatin + apelin-13 group, however, pyramidal neuron and glial cell damage was less than those without apelin-13. Cisplatin increased TrkB activity in the hippocampus, which was counteracted by apelin-13. In conclusion, apelin-13 reduced the cisplatin-induced cognitive deficiency, by suppressing inflammation and stimulating the synthesis and activation of neurotrophic factors in hippocampal tissue.

Effects of melatonin on oxidative stress and spatial memory impairment induced by acute ethanol treatment in rats

Melatonin has recently been suggested as an antioxidant that may protect neurons from oxidative stress. Acute ethanol administration produces both lipid peroxidation as an indicator of oxidative stress in the brain and impairs water-maze performance in spatial learning and memory tasks. The present study investigated the effect of melatonin against ethanol-induced oxidative stress and spatial memory impairment. The Morris water maze was used to evaluate the cognitive functions of rats. Thiobarbituric acid reactive substances (TBARS), which are the indicators of lipid peroxidation, and the activities of antioxidative enzymes (glutathione peroxidase and superoxide dismutase) were measured in the rat hippocampus and prefrontal cortex which form interconnected neural circuits for spatial memory. Acute administration of ethanol significantly increased TBARS levels in the hippocampus. Combined melatonin-ethanol treatment caused a significant increase in glutathione peroxidase activities and a significant decrease of TBARS in the rat hippocampus. In the prefrontal cortex, there was only a significant decrease of TBARS levels in the combined melatonin-ethanol receiving group as compared to the ethanol-treated group. Melatonin did not affect the impairment of spatial memory due to acute ethanol exposure, but melatonin alone had a positive effect on water maze performances. Our study demonstrated that melatonin decreased ethanol-induced lipid peroxidation and increased glutathione peroxidase activity in the rat hippocampus.