Ningbo Cai,Bingtian Xu,Xing Li,Yunyun Qin,Mengfan Li,Kechun Chen,Jiangping Xu,Haitao Wang
The loss of tight junction (TJ) and adherens junction (AJ) proteins leads to the damage of the blood-brain barrier (BBB) during cerebral ischemia . Inhibition of cyclic nucleotide phosphodiesterase 4 (PDE4) by roflumilast (Roflu) protects against ischemic stroke-induced neuronal damage. However, the effects of Roflu on vascular endothelial injury and BBB integrity remain unknown. Here, we investigated whether and how Roflu protects against cerebrovascular endothelial injury caused by cerebral ischemia/reperfusion. We demonstrated that PDE4B knocking-down increased the expression of TJ and AJ proteins in human brain microvascular endothelial cells (HBMECs) subjected to oxygen-glucose deprivation reperfusion (OGD/R). Inhibition of PDE4 by Roflu (1.0 μM) showed similar effects as PDE4B knocking-down. We then found that Roflu activated Notch1/Hairy and enhancer of split 1 (Hes1) signaling. Consistently, the effects of Roflu on TJ and AJ proteins were reversed by the γ-secretase inhibitor DAPT or Hes1 knocking-down. Furthermore, Roflu (1.0 mg/kg) improved neurobehavioral outcomes and ameliorated BBB disruption in rats following ischemic stroke. Roflu also increased the levels of TJ proteins and AJ proteins in vivo . Collectively, these data suggest that Roflu is a promising compound for the prevention of BBB damage. The protective effects of Roflu are mediated through activation of the Notch1/Hes1 pathway.
Kechun Chen,Bingtian Xu,Shuqin Qiu,Lu Long,Qian Zhao,Jiangping Xu,Haitao Wang
We have previously shown that phosphodiesterase 4 (PDE4) inhibition protects against neuronal injury in rats following middle cerebral artery occlusion/reperfusion (MCAO/R). However, the effects of PDE4 on brain edema and astrocyte swelling are unknown. In this study, we showed that inhibition of PDE4 by Roflumilast (Roflu) reduced brain edema and brain water content in rats subjected to MCAO/R. Roflu decreased the expression of aquaporin 4 (AQP4), while the levels of phosphorylated protein kinase B (Akt) and forkhead box O3a (FoxO3a) were increased. In addition, Roflu reduced cell volume and the expression of AQP4 in primary astrocytes undergoing oxygen and glucose deprivation/reoxygenation (OGD/R). Consistently, PDE4B knockdown showed similar effects as PDE4 inhibition; and PDE4B overexpression rescued the inhibitory role of PDE4B knockdown on AQP4 expression. We then found that the effects of Roflu on the expression of AQP4 and cell volume were blocked by the Akt inhibitor MK2206. Since neuroinflammation and astrocyte activation are the common events that are observed in stroke, we treated primary astrocytes with interleukin-1β (IL-1β). Astrocytes treated with IL-1β showed decreased AQP4 and phosphorylated Akt and FoxO3a. Roflu significantly reduced AQP4 expression, which was accompanied by increased phosphorylation of Akt and FoxO3a. Furthermore, overexpression of FoxO3a partly reversed the effect of Roflu on AQP4 expression. Our findings suggest that PDE4 inhibition limits ischemia-induced brain edema and astrocyte swelling via the Akt/FoxO3a/AQP4 pathway. PDE4 is a promising target for the intervention of brain edema after cerebral ischemia.
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