Calcium-independent CaMKII activity is involved in ginsenoside Rb1-mediated neuronal recovery after hypoxic damage

Recent studies have indicated that Ginsenoside Rb1, one of the major components of ginseng root, may play an important role in protecting cells from damage. Here, we investigated the neuroprotective activity of Rb1 after hypoxic injury in young rats. About 50% animals were dead by exposing hypoxic condition three times in three consecutive days. Then, the pretreatment with Rb1 prior to hypoxic stimulation reduced animal death to 12%, and also significantly reduced the recovery time from hypoxia-related, compromised symptoms in survived animals. Rb1 also significantly reduced levels of lactate dehydrogenase (LDH) release from primary hippocampal neurons which were maintained at low oxygen concentration, indicating increased neuronal survival by Rb1. Ca2+/calmodulin-dependent kinase II (CaMKII) activity in the hippocampal tissues of hypoxia-induced rats was decreased to about 50% of the control animal. Then Rb1-treatment prior to hypoxic stimulation significantly elevated Ca2+-independent kinase II activity when measured 48 hr after hypoxic stimulation. Thus, the present data suggest that calcium independent CaMKII activity may be involved in the process of ginsenoside Rb1-mediated recovery of neuronal cells after hypoxic damage.