Melatonin attenuates fentanyl - induced behavioral sensitization and circadian rhythm disorders in mice.

Melatonin is a neurohormone synthesized by the pineal gland to regulate the circadian rhythms and has proven to be effective in treating drug addiction and dependence. However, the effects of melatonin to modulate the drug-seeking behavior of fentanyl and its underlying molecular mechanism is elusive. This study was designed to investigate the effects of melatonin on fentanyl - induced behavioral sensitization and circadian rhythm disorders in mice. The accompanying changes in the expression of Brain and Muscle Arnt-Like (BMAL1), tyrosine hydroxylase (TH), and monoamine oxidase A (MAO-A) in relevant brain regions including the suprachiasmatic nucleus (SCN), nucleus accumbens (NAc), prefrontal cortex (PFC), and hippocampus (Hip) were investigated by western blot assays to dissect the mechanism by which melatonin modulates fentanyl - induced behavioral sensitization and circadian rhythm disorders. The present study suggest that fentanyl (0.05, 0.1 and 0.2 mg/kg) could induce behavioral sensitization and melatonin (30.0 mg/kg) could attenuate the behavioral sensitization and circadian rhythm disorders in mice. Fentanyl treatment reduced the expression of BMAL1 and MAO-A and increased that of TH in relevant brain regions. Furthermore, melatonin treatment could reverse the expression levels of BMAL1, MAO-A, and TH. In conclusion, our study demonstrate for the first time that melatonin has therapeutic potential for fentanyl addiction.

The Dual Role of AQP4 in Cytotoxic and Vasogenic Edema Following Spinal Cord Contusion and Its Possible Association With Energy Metabolism via COX5A.

Spinal cord edema, mainly including vasogenic and cytotoxic edema, influences neurological outcome after spinal cord contusion (SCC). Aquaporin 4 (AQP4) is the most ubiquitous water channel in the central nervous system (CNS), which is a rate-limiting factor in vasogenic edema expressing in brain injury, and it contributes to the formation of cytotoxic edema locating in astrocytes. However, little is known about the regulatory mechanism of AQP4 within vasogenic and cytotoxic edema in SCC, and whether the regulation mechanism of AQP4 is related to Cytochrome coxidase (COX5A) affecting energy metabolism. Therefore, the SCC model is established by Allen's method, and the degree of edema and neuronal area is measured. The motor function of rats is evaluated by the Basso, Beattie, and Bresnahan (BBB) scoring system. Meanwhile, AQP4 and COX5A are detected by real-time quantitative PCR (qRT-PCR) and western blot (WB). The localization of targeted protein is exhibited by immunohistochemical staining (IHC) and immunofluorescence (IF). Additionally, the methodology of AQP4 lentivirus-mediated RNA interference (AQP4-RNAi) is used to reveal the effect on edema of SCC and the regulating molecular mechanism. Firstly, we observe that the tissue water content increases after SCC and decreases after the peak value of tissue water content at 3 days (P < 0.05) with abundant expression of AQP4 protein locating around vascular endothelial cells (VECs), which suggests that the increasing AQP4 promotes water reabsorption and improves vasogenic edema in the early stage of SCC. However, the neuronal area is larger than in the sham group in the 7 days (P < 0.05) with the total water content of spinal cord decrease. Meanwhile, AQP4 migrates from VECs to neuronal cytomembrane, which indicates that AQP4 plays a crucial role in aggravating the formation and development of cytotoxic edema in the middle stages of SCC. Secondly, AQP4-RNAi is used to elucidate the mechanism of AQP4 to edema of SCC. The neuronal area shrinks and the area of cytotoxic edema reduces after AQP4 downregulation. The BBB scores are significantly higher than in the vector group after AQP4-RNAi at 5, 7, and 14 (P < 0.05). There is a relationship between AQP4 and COX5A shown by bioinformatics analysis. After AQP4 inhibition, the expression of COX5A is significantly upregulated in the swelling astrocytes. Therefore, the inhibition of AQP4 expression reduces cytotoxic edema in SCC and improves motor function, which may be associated with upregulation of COX5A via affecting energy metabolism. Moreover, it is not clear how the inhibition of AQP4 directly causes the upregulation of COX5A.

Lentivirus-mediated inhibition of AQP4 accelerates motor function recovery associated with NGF in spinal cord contusion rats.

Aquaporin-4 (AQP4) is a water channel protein in spinal cord and plays a critical role in the pathophysiological process of spinal cord injury (SCI). However, little is known about the molecular mechanism of AQP4 involved in SCI. The present study was performed to investigate the possible molecules regulated by AQP4 after SCI by use of lentivirus-mediated RNA interference (RNAi). First, the motor function was evaluated by Basso, Beattie, Bresnahan (BBB) scale and the expression of AQP4 was measured by western blot, immunohistochemical staining and immunofluorescence in rats after contusion spinal cord injury (cSCI). After cSCI, the rats exhibited a gradual motor function recovery from 3dpo to 28dpo. And the expression and localization of AQP4 changed with different post-injury stages. At 3d after SCI, AQP4 located mainly in vascular endothelial cells (VECs) in the anterior horn of spinal cord, which was similar to the sham rats. At 7d and 28d after SCI, AQP4 was expressed both in VECs and the position of neuron membranes. The protein level of AQP4 increased significantly at 12h, 1d and 3d after SCI, and decreased slightly at 7d after SCI. Then lentivirus-mediated AQP4 RNA interference (AQP4-RNAi) was constructed and used to inhibit AQP4 expression in cSCI rats. The results from real-time quantitative polymerase chain reactions (RT-qPCR) and immunohistochemical staining suggested that the expression of nerve growth factor (NGF) was up-regulated by lentivirus-mediated AQP4 inhibition in cSCI rats, while the motor function recovery was accelerated. The results suggested that the acceleration of motor function recovery by AQP4 inhibition was associated with NGF up-regulation. This is the first report on the relationship between AQP4 and NGF in SCI, which may shed light on illustrating the role of AQP4 in SCI. These findings may also provide strategies of the clinical treatment for SCI in the future.