Therapeutic hypercapnia reduces blood-brain barrier damage possibly via protein kinase Cε in rats with lateral fluid percussion injury.

BACKGROUND: This study investigated whether therapeutic hypercapnia (TH) ameliorated blood-brain barrier (BBB) damage and improved the neurologic outcome in a rat model of lateral fluid percussion injury (FPI), and explored the possible underlying mechanism. METHODS: Rats underwent lateral FPI and received inhalation of 30%O2-70%N2 or 30%O2-N2 plus CO2 to maintain arterial blood CO2 tension (PaCO2) between 80 and 100 mmHg for 3 h. To further explore the possible mechanisms for the protective effects of TH, a PKC inhibitor staurosporine or PKCαß inhibitor GÖ6976 was administered via intracerebral ventricular injection. RESULTS: TH significantly improved neurological function 24 h, 48 h, 7 d, and 14 d after FPI. The wet/dry ratio, computed tomography values, Evans blue content, and histological lesion volume were significantly reduced by TH. Moreover, numbers of survived neurons and the expression of tight junction proteins (ZO-1, occludin, and claudin-5) were significantly elevated after TH treatment at 48-h post-FPI. TH significantly increased the expression of protein kinase Cε (PKCε) at 48-h post-FPI, but did not significantly change the expression of PKCα and PKCßII. PKC inhibitor staurosporine (but not the selective PKCαß inhibitor-GÖ6976) inhibited the protective effect of TH. CONCLUSIONS: Therapeutic hypercapnia is a promising candidate that should be further evaluated for clinical treatment. It not only protects the traumatic penumbra from secondary injury and improves histological structure but also maintains the integrity of BBB and reduces neurologic deficits after trauma in a rat model of FPI.