Abstract: BACKGROUND: Croton cream can activate ERK pathways and have anti-apoptotic effects on neuronal cells. It is not clear whether it synergistically exerts anti-apoptotic effects by inhibiting the activation of JNK and p38 pathways.
OBJECTIVE: To explore the effects and mechanisms of croton cream on neuronal damage and apoptosis in the ischemic cortex of rats with cerebral ischemia-reperfusion injury.
METHODS: (1) Ninety Sprague-Dawley rats were randomly divided into sham operation group, model group, croton cream low-dose group, croton cream medium-dose group, croton cream high-dose group and nimodipine group, with 15 rats in each group. Except for the sham operation group, animal models of middle cerebral artery occlusion were prepared in rats by the thread method. Rats in the three croton cream groups were given 20, 40, and 60 mg/kg croton cream, respectively. Rats in the sham operation and model groups were given the same amount of normal saline, once a day, for 7 consecutive days. The optimal concentration of croton cream, namely the high dose of croton cream, was selected based on neurological deficit score, TTC staining, brain tissue water content, hematoxylin-eosin staining and Nissl staining. (2) Another 120 Sprague-Dawley rats were randomly divided into sham operation group, model group, croton cream group, JNK inhibitor group, croton cream+JNK inhibitor group, p38 MAPK inhibitor group, croton cream+p38 MAPK inhibitor group, and nimodipine group, with 15 rats in each group. Animal models of middle cerebral artery occlusion were prepared using the thread method in all the groups except in the sham operation group. Thirty minutes before modeling, 10 μL of SP600125 (JNK inhibitor) and 10 μL of SB203580 (p38 MAPK inhibitor) were injected into the lateral ventricle of the rats, respectively. Rats in croton cream groups were intragastrically given 60 mg/kg croton cream. Seven days later, the JNK/p38 MAPK signaling pathway, apoptosis-related proteins and cell apoptosis were detected by western blot, TUNEL staining and flow cytometry, respectively.
RESULTS AND CONCLUSION: (1) Compared with the sham operation group, neurological deficit score, cerebral water content, cerebral infarction volume and apoptosis rate were significantly increased in the model group (P < 0.05), where nerve cells showed scattered distribution. Compared with the model group, neurological deficit score, water content of brain tissue and cerebral infarction volume were significantly decreased in the croton cream medium-dose group, high-dose group and nimodipine group (P < 0.05), and the pathological morphology of nerve cells was significantly improved. (2) Compared with the JNK inhibitor group, p-JNK/JNK, p-p38/p38 and Bax expressions in rat brain tissue and the apoptotic rate were significantly decreased in the croton cream+inhibitor groups (P < 0.05), while the expression of and Bcl-2 was significantly increased (P < 0.05). To conclude, croton cream may inhibit the activation of JNK/p38 MAPK signaling pathway and reduce neuronal apoptosis to achieve neuroprotective effects in rats with cerebral ischemia-reperfusion injury.

Key words: croton cream, cerebral ischemia-reperfusion injury, neuronal apoptosis, signaling pathway, rat