Role of the p38MAPK signaling pathway in hippocampal neuron autophagy in rats with chronic intermittent hypoxia.

Abstract

This study explored the role of the p38 mitogen-activated protein kinase (MAPK) signaling pathway in hippocampal neuron autophagy in rats with chronic intermittent hypoxia (CIH). Sixty-four male Sprague-Dawley rats were randomly divided to normoxic control (CON), CIH (subdivided into groups A, B, and C undergoing intermittent hypoxia for 2, 4, and 6 weeks, respectively), solvent (CIH+Veh), or p38MAPK inhibitor (CIH+SB203580) groups. DMSO and SB203580 were injected intraperitoneally 30 min before hypoxia in CIH+Veh and CIH+SB203580 group rats, respectively. Rat learning and memory were evaluated via the Morris water maze test. Ultrastructural changes in the hippocampal CA1 region autophagic vesicles and neurons were observed under transmission electron and light microscopy. Hippocampal microtubule-associated proteins were detected by western blot. Morris water maze test showed that CIH+SB203580 group rats spent significantly more time on the platform quadrant and crossed the platform more times than CIH+Veh group rats (P < 0.01). HE staining showed greater rat cell damage in the CIH+SB group than in the CIH and CIH+Veh groups. Western blot analysis showed that CIH+SB group rats had significantly lower p-p38MAPK/p38MAPK, LC3I, and p62 expression and higher beclin-1 expression than CIH+Veh group rats (P < 0.01). Electron microscopy showed that CIH+SB203580 group rats had several small hippocampal neuron autophagic vesicles. On immunofluorescence analyses, it showed a higher LC3II expression in CIH+SB203580 group rats than in CIH+Veh group rats (P < 0.01). These results indicate that inhibition of the CIH p38MAPK signaling pathway can activate autophagy and protect hippocampal neurons in rats.