Effects of chronic cerebral hypoperfusion and low-dose progesterone treatment on apoptotic processes, expression and subcellular localization of key elements within Akt and Erk signaling pathways in rat hippocampus.

ABSTRACT

The present study attempted to investigate how chronic cerebral hypoperfusion (CCH) and repeated low-dose progesterone (P) treatment affect gene and protein expression, subcellular distribution of key apoptotic elements within protein kinase B (Akt) and extracellular signal-regulated kinases (Erk) signal transduction pathways, as well as neurodegenerative processes and behavior. The results revealed the absence of Erk activation in CCH in cytosolic and synaptosomal fractions, indicating a lower threshold of Akt activation in brain ischemia, while P increased their levels above control values. CCH induced an increase in caspase 3 (Casp 3) and poly (ADP-ribose) polymerase (PARP) gene and protein expression. However, P restored expression of examined molecules in all observed fractions, except for the levels of Casp 3 in synapses which highlighted its possible non-apoptotic or even protective function. Our study showed the absence of nuclear factor kappa-light-chain-enhancer of activated b cells (NF-κB) response to this type of ischemic condition and its strong activation under the influence of P. Further, the initial increase in the number of apoptotic cells and amount of DNA fragmentation induced by CCH was significantly reduced by P. Finally, P reversed the CCH-induced reduction in locomotor activity, while promoting a substantial decrease in anxiety-related behavior. Our findings support the concept that repeated low-dose post-ischemic P treatment reduces CCH-induced neurodegeneration in the hippocampus. Neuroprotection is initiated through the activation of investigated kinases and regulation of their downstream molecules in subcellular specific manner, indicating that this treatment may be a promising therapy for alleviation of CCH-induced pathologies.