Progesterone promotes axonal regeneration after cerebral hemorrhage and related mechanisms in rats

Abstract

Objective To determine the effect of progesterone on axon regeneration of cerebral ganglia neurons after intracerebral hemorrhage (ICH), and explore the underlying mechanism. Methods SD rats were randomly divided into ICH group, low- (8 mg/kg) and high-dose progesterone (16 mg/kg) groups, and sham operation group. Combined treatment of high-dose progesterone and PI3K/Akt pathway inhibitor LY294002 was given to the rats from the inhibitor group. The neurological deficits, brain water content and pathological changes and expression of axon growth-related proteins were observed at 1, 3, 7 and 14 d after operation. And the cerebral hematoma volume and oxidative stress related indexes were analyzed at 3 d after operation. The expression levels of axonal-associated proteins and pathway proteins p-Akt and RhoA were detected at 3 d after operation, and the locations of GAP43 and p-Akt/RhoA were identified with immunofluorescence staining. Results The ICH group had severest neurological dysfunction and cerebral edema at each time point, and largest volume of cerebral hematoma and highest levels of oxidative stress products. After progesterone intervention, the damage was relieved at each time point, with the efficacy of high-dose more obvious than low-dose (P < 0.05). Western blot Results showed that the high-dose progesterone intervention increased the expression levels of GAP43 and NF200 and decreased those of MAG and Nogo-A when compared to the low-dose progesterone and ICH groups (P < 0.05). Western blot analysis indicated that the expression of GAP43, NF200 and p-Akt was down-regulated while that of MAG, Nogo-A and RhoA was increased in the inhibitor group compared with the high- and low-dose progesterone groups (P < 0.05). The Results of double-labeled fluorescence staining showed that the expression of p-Akt was increased and that expression of RhoA was decreased in neuronal cells of the high-dose progesterone group compared with ICH group (P < 0.05). Conclusion Progesterone improves neurological dysfunction after cerebral hemorrhage and promotes regeneration and repair of damaged axons, which may be related to activation of PI3K/Akt pathway and inhibition of RhoA expression.

Keywords

• cerebral hemorrhage
• axonal regeneration
• progesterone
• neurological dysfunction