The Neuroprotective Effects Of Parecoxib And Prostatic Acid Phosphatase Against Focal Cerebral Ischemic Injury In Rats

Stroke is a leading cause of morbidity and mortality in China. The mortality rate of stroke during perioperative period is as high as 60%. Thrombolysis is currently the only effective therapy available for stroke. Its clinical use, however, is rather limited, becauce of serious complications and relatively narrow therapeutic time window. Development of novel drugs for cerebral ischemic injury is a necessity.A large number of studies have shown that the generation of inflammation in stroke is one of the pathophysiologic mechanisms. The inflammation-related enzymes such as cyclooxygenase-2 (COX-2) plays an important role in the cerebral ischemic injury. Administration of highly selective COX-2 inhibitor has been proven to have the neuroprotective effect. Parecoxib is the only one of selective COX-2 inhibitors that can be use for intravenous injection. One of the goals of this study was to examine the dose-response relationship and the therapeutic time window of Parecoxib on focal cerebral ischemia-reperfusion (I-R) injury in rats. A great body of evidence has been accumulating in the last 30 years supporting a role for adenosine as an endogenous neuroprotectant against brain ischemia. Though the potential use of adenosine as a neuroprotective agent in the context of stroke has long been realized, there are currently no adenosine-based therapies for the treatment of cerebral ischemia and reperfusion, because extracellular adenosine can rapidly metabolized by adenosine kinase to form AMP, or by adenosine deaminase to form inosine. Further clinical development of adenosine-based therapies calls for approaches of slow and sustained delivery of adenosine.It has been recently reported that the soluble and secreted prostatic acid phosphatase (PAP), an enzyme that has long served as a diagnostic marker for prostate cancer, has a membrane-bound splice variant. This enzyme exhibits ecto-5’-nucleotidase activity, is widely distributed, and implicated in the formation of chronic pain. Single intraspinal injection of the recombinant soluble (secreted form) of human PAP (hPAP) protein had potent antinociceptive, antihyperalgesic, and antiallodynic effects that lasted for several days. Additional experiments implied that injected PAP dephosphorylates endogenous extracellular AMP to adenosine and exerts its function via activation of A1 adenosine receptors. These novel data suggest that PAP could be taken into account as an approach of sustained production of adenosine.We therefore hypothesize that PAP has sustained and potent neuroprotective effects against cerebral ischemia. To explore this potential function, we performed this study to examine the effects of hPAP on infarct size and neurological behavior scores in the rat model of middle cerebral artery occlusion (MCAO). Part 1The therapeutic effict of selective cyclooxygenase-2 inhibitor Parecoxib on ischemia-reperfusion injury in ratsObjective The goal of this study was to examine the dose-response relationship and the therapeutic time window of Parecoxib (Pa) on focal cerebral ischemia-reperfusion (I-R) injury in rats.Methods (1) Male SD rats weighed 250-280g were randomly divided into 6 groups: I-R, Vehicle, Pa1 (5mg/kg), Pa2 (10mg/kg) , Pa3 (20mg/kg) and Pa4 (40mg/kg). Parecoxib or vehicle was intraperitoneally administered to the corresponding groups at 15min before the establishment of cerebral I-R model by middle cerebral artery occlusion (MCAO) for 120min. The neurologic behavior score (NBS) was evaluated at 24h after reperfusion by Garcia method. The cerebral infarct volume percentage (CIVP) was then assessed by 10 g/L TTC staining following the last neurological outcome evaluation.(2) Male SD rats were treated with parecoxib randomly 15min before or 1.5h , 3h and 6h after cerebral reperfusion. The I-R model was established and NBS and CIVP were recorded as mentioned above.Results (1) The NBS in groups Pa2, Pa3 at 24h after I-R was significantly higher than that in I-R group; the CIVP was reduced significantly than that in I-R group. There was no difference in NBS and CIPV between Vehicle and I-R groups. (2) Parecoxib treatment was associated with a decrease in infarction volume when administered 15 min before, and at 1.5h or 3h after cerebral reperfusion. Part 2The neuroprotective effects of Prostatic acid phosphatase against focal cerebral ischemic injury in ratsObjective The goal of this study was to examine the dose-response relationship and therapeutic time window of Prostatic acid phosphatase (PAP) on focal cerebral ischemia injury in rats.Methods (1) Male SD rats weighed 250-280g were randomly divided into 7 groups (n=6 in each group): MCAO, Vehicle and PAP (100mU、300mU、1000mU、3000mU和10000mU). PAP or vehicle was Intracerebroventricular administered to the corresponding groups at 6h before the establishment of cerebral I-R model by middle cerebral artery occlusion (MCAO) for 120min. The neurologic behavior score (NBS) was evaluated at 24h after reperfusion by Garcia method. The cerebral infarct volume percentage (CIVP) was then assessed by 10 g/L TTC staining following the last neurological outcome evaluation.(2) Male SD rats weighed 250-280g were randomly divided into 7 groups (n=7 in each group): MCAO and PAP (PAP intracerebroventricular administration at 6h before or onestet of MCAO or 1.5h , 3h, 4.5 and 6h after induction of cerebral ischemia). The NBS and CIVP were recorded as mentioned above.Results (1) The NBS in groups PAP1000 and PAP3000 at 24h after I-R was significantly higher than that in MCAO group; the CIVP was reduced significantly than that in MCAO group. There was no difference in NBS and CIPV between Vehicle and MCAO groups. (2)PAP treatment was associated with a decrease in infarction volume when administered 6h before, and at 1.5h after cerebral ischemia. Conclusion1. Parecoxib significantly reduces focal cerebral ischemia-reperfusion injury in rats. Its optimal protective dose is 20mg/kg, and therapeutic time window is from 15min before ischemia to 3h after reperfusion.2. PAP significantly reduces focal cerebral ischemia-reperfusion injury in rats. Its optimal protective dose is 1000mU, and therapeutic time window is from 6h before ischemia to 1.5h after reperfusion.3. The present study suggested that both Parecoxib and PAP could be novel drugs for the prevention and treatment of cerebral ischemic injury during perioperative period.