Combined treatment of retinoic acid with olfactory ensheathing cells protect gentamicin-induced SGNs damage in the rat cochlea in vitro.

Hearing is mainly dependent on the function of hair cells (HCs) and spiral ganglion neurons (SGNs) which damage or loss of them leads to irreversible hearing loss. Olfactory ensheathing cells (OECs) are specialized glia that forms the fascicles of the olfactory nerve by surrounding the olfactory sensory axons. The OECs, as a regenerating part of the nervous system, play a supporting function in axonal regeneration and express a wide range of growth factors. In addition, retinoic acid (RA) enhances the proliferation and differentiation of these cells into the nerve. In the present study, we co-cultured human OECs (hOECs) with cochlear SGNs in order to determine whether hOECs and RA co-treatment can protect the repair process in gentamycin-induced SGNs damage in vitro. For this purpose, cochlear cultures were prepared from P4 Wistar rats, which were randomly appointed to four groups: normal cultivated SGNs (Control), gentamicin-lesioned SGNs culture (Gent), gentamicin-lesioned SGNs culture treated with OECs (Gent + OECs) and gentamicin-lesioned SGNs culture co-treated with OECs and RA (Gent + OEC& RA). The expression of a specific protein in SGNs was examined using immunohistochemical and Western blotting technique. TUNEl staining was used to detect cell apoptosis. Here, we revealed that combined treatment of OECs and RA protect synapsin and Tuj-1 expression in the lesioned SGNs and attenuate cell apoptosis. These findings suggest that RA co-treatment can enhance efficiency of OECs in repair of SGNs damage induced by ototoxic drug.

Neuroprotective effect of berberine chloride on cognitive impairment and hippocampal damage in experimental model of vascular dementia.

OBJECTIVES: The major objective of the present study was to investigate the potential neuroprotective effect of berberine chloride on vascular dementia. Berberine, as an ancient medicine in China and India, is the main active component derived from the Berberis sp. Several studies have revealed the beneficial effects of berberine in various neurodegenerative disorders. MATERIALS AND METHODS: To induce vascular dementia, chronic bilateral common carotid artery occlusion was performed on male Wistar rats. After surgery, the rats were treated daily by oral administration of berberine chloride (50 mg/kg) for two months. The cognition function of treated rats, were evaluated by Morris Water Maze (MWM) test. In addition, Nissl and TUNEL staining were chosen to assess neuronal damage within the hippocampal CA1 area. RESULTS: It was obvious that chronic cerebral hypoperfusion (CCH), caused cognitive impairment and neuronal damages within CA1 hippocampal subregion. Berberine chloride was able to prevent cognitive deficits, (P<0.05) and reversed CCH-induced hippocampal neuronal loss and apoptosis, (P<0.05). CONCLUSION: Berberine chloride may be considered as a potential treatment for cognitive deficits and neuronal injury caused by CCH in the hippocampal CA1 area.

The role of erythropoietin in remote renal preconditioning on hippocampus ischemia/reperfusion injury.

Remote ischemic preconditioning (RIPC) is an intriguing approach which exposes a remote organ/tissue to a non-lethal transient ischemia/reperfusion (I/R) in order to potentiate the resistance of the desired organ/tissue against the next unwanted I/R. It has been suggested that RIPC exerts its effect through neuronal and hormonal pathways. The underlying mechanisms of RIPC are obscure and should be elucidated. In this study, we induced RIPC in mice using 3 cycles of 5 min ischemia alternating with 5 min reperfusion of the left renal artery. Renal failure was induced in mice by intra-peritoneal (i.p.) injection of 200 mg/kg body weight of gentamicin twice per day for 4 consecutive days. Global hippocampal ischemia reperfusion (I/R) was performed by bilateral carotid artery occlusion for 20 min followed by reperfusion for 72 h. Moreover, the retention trial of passive avoidance test was determined 72 h after global ischemia. Histopathological changes of hippocampus neurons were observed using Nissl staining to detect neuronal loss. Finally, terminal deoxynucleotidyl transferase mediated dUTP nick end-labeling (TUNEL) was performed to assess the status of apoptotic cells in the hippocampus. The results of this study suggest that renal ischemic preconditioning is a good candidate for prevention of I/R-induced hippocampal injury. However, RRPC (remote renal preconditioning) failed to exert a neuroprotective effect in mice with renal failure (RF), indicating the probable role of a humoral factor which is released from kidneys in response to ischemia. In agreement with this hypothesis, treatment of mice with rhEPO (5000 IU/kg intraperitoneal) before induction of RRPC restored the neuroprotective effects of RRPC in RF mice. Accordingly, it is plausible to expect that erythropoietin is released from kidneys to act as a mediator for RRPC-induced neuroprotective effects. Renal ischemic preconditioning prevents I/R-induced hippocampal injury. In contrast, renal failure hampers protective effects of RRPC, while exogenous administration of erythropoietin (EPO) significantly prevents the inhibiting effects of renal failure.

Role of morphine preconditioning and nitric oxide following brain ischemia reperfusion injury in mice.

OBJECTIVES: Morphine dependence (MD) potently protects heart against ischemia reperfusion (IR) injury through specific signaling mechanisms, which are different from the pathways involved in acute morphine treatment or classical preconditioning. Since opioid receptor density changes post cerebral ischemia strongly correlated with brain histological damage, in the present study, we tried to elucidate the possible role of opioid receptors in IR injury among morphine-dependent mice. MATERIALS AND METHODS: Accordingly, incremental doses (10 mg/kg/day to 30 mg/kg/day) of morphine sulphate were subcutaneously administered for 5 days before global brain ischemia induction through bilateral common carotid artery occlusion. Animals were received naloxone (5 mg/kg) or L-NAME (20 mg/kg) 30 min after the last morphine dose. Twenty four hr after the ischemia induction, Retention trial of passive avoidance test and western blot analysis were done. histological analysis (TUNEL and NISSL staining) performed 72 hr after ischemia. RESULTS: MD improved post ischemia memory performance (P<0.01) and neuronal survival (P<0.001) and decreased apoptosis (P<0.05) in region I of hippocampus (CA1 region) in mouse. Treatment with naloxone or L-NAME abolished all MD aforementioned effects. CONCLUSION: Results of the present study suggested that opioid receptors activation in the early hr post ischemia is crucial for MD-induced hippocampus tolerance against IR injury. Opioid receptor-dependent balance of NO production was another key factor in MD-induced protection. Further studies are required to determine the effect of MD on opioid receptor changes after ischemia and its correlation with MD-induced protection.

The Protective Effect of Remote Renal Preconditioning Against Hippocampal Ischemia Reperfusion Injury: Role of KATP Channels.

Remote ischemic preconditioning (RIPC), which consists of several brief ischemia/reperfusion applied at the remote site of lethal ischemia reperfusion, can, through activating different mechanisms, increase the ability of the body's endogenous protection against prolonged ischemia/reperfusion. Recent studies have shown that RIPC has neuroprotective effects, but its mechanisms are not well elucidated. The present study aimed to determine whether activation of KATP channels in remote renal preconditioning decreases hippocampus damage induced by global cerebral ischemia. RIPC was induced by ischemia of the left renal artery (IPC); 24 h later, global cerebral ischemia reperfusion (IR) was induced by common carotid arteries occlusion. 5hydroxydecanoate (5HD) and glibenclamide (Gli) were injected before of IPC. The levels of malondialdehyde (MDA) and catalase (CAT) activity were assessed in hippocampus. Terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) was assessed to detect apoptotic cells in hippocampus. RIPC inhibited apoptosis by decreasing positive TUNEL cells (P < 0.05). KATP channels blocking with 5HD and Gli markedly increased apoptosis in hippocampal cells in RIPC group (P < 0.001). RIPC decreased MDA level and increased CAT activity in ischemic hippocampus (P < 0.01). Also, 5HD and Gli inhibited the effect of RIPC on MDA level and CAT activity (P < 0.05). The present study shows that RIPC can effectively attenuate programmed cell death, increase activity of CAT, and reduce MDA levels. Blocking of KATP channels inhibited the protective effects of RIPC.

Hydrogen sulfide protects the brain against ischemic reperfusion injury in a transient model of focal cerebral ischemia.

Hydrogen sulfide (H(2)S), a well-known toxic gas, is regarded as endogenous neuromodulator and plays multiple roles in the central nervous system under physiological and pathological states, especially in secondary neuronal injury. Recent studies have shown relatively high concentrations of hydrogen sulfide (H(2)S) in the brain and also cytoprotective effects of endogenous and exogenous H(2)S in models of in vitro and in vivo ischemic injury. H(2)S protects neurons by functioning as an anti-oxidant, anti-inflammatory, and anti-apoptotic mediator and by improving neurological function. Moreover, it protects neurons from glutamate toxicity. Therefore, the present study aimed to determine whether H(2)S provides protection in transient focal cerebral ischemia. Focal ischemia was induced by 60-min middle cerebral artery occlusion (MCAO), followed by 23-h reperfusion. Saline as a vehicle and NaHS (H(2)S donor; 1 and 5 mg) were intraperitoneally injected (IP) at the beginning of ischemia. Infarct volume, brain edema, and apoptosis were assessed 24 h after MCAO.Treatment with NaHS at doses of 1 and 5 mg markedly reduced total infarct volumes by 29 and 51 %, respectively (P < 0.001). In addition, NaHS at doses of 1 and 5 mg reduced brain edema (P < 0.05) and inhibited apoptosis by decreasing positive TUNEL cells (P < 0.001).The present study shows that treatment with H(2)S reduces brain injuries and postischemic cerebral edema in a dose-dependent manner likely through the blocking programmed cell death.We propose that H(2)S might be a promising therapeutic target for stroke, although more researches are necessary to take into account the potential therapeutic effects of H(2)S in stroke patients.