LS21013A-06, a PDE4 inhibitor, preserves blood-brain barrier integrity in experimental ischemic stroke models through PKA-dependent modulation of LECT2.

Ischemic stroke (IS) disrupts the blood-brain barrier (BBB), thereby aggravating neurological deterioration. Loss of tight junction (TJ) and adherens junction (AJ) proteins is a key event in BBB breakdown, but the upstream mechanisms remain incompletely understood. Here, we investigated whether LS21013A-06 (A06), a phosphodiesterase-4 inhibitor, protects brain microvascular endothelial cells and preserves BBB integrity after ischemia/reperfusion, with particular focus on whether its protective effects are PKA-dependent and accompanied by changes in leukocyte cell-derived chemotaxin-2 (LECT2). In human brain microvascular endothelial cells subjected to oxygen-glucose deprivation/reperfusion (OGD/R), LECT2 knockdown preserved TJ and AJ proteins, reduced Bax upregulation, restored Bcl-2 expression, and diminished reactive oxygen species accumulation. A06 pretreatment (3 μM) recapitulated these effects and markedly reduced OGD/R-induced LECT2 expression. The PKA inhibitor H89 (5 μM) abolished A06-mediated LECT2 suppression, junctional preservation, and reductions in apoptosis and reactive oxygen species, whereas LECT2 overexpression similarly abrogated the protective effects of A06. In a rat middle cerebral artery occlusion/reperfusion (MCAO/R) model, post-ischemic A06 administration (1 or 3 mg/kg, intraperitoneally) improved neurological scores and motor performance, reduced infarct volume and Evans blue extravasation, and increased ZO-1, VE-cadherin, and Occludin levels in peri-infarct cortex, together with reduced LECT2 expression and attenuated apoptosis-related changes in Bcl-2 and Bax. These findings indicate that A06 preserves BBB integrity after experimental ischemia. Mechanistically, its protective effects were PKA-dependent and accompanied by reduced LECT2 levels, preserved junctional proteins, and attenuated apoptosis-related changes. A06 enhanced PKA signaling, whereas PKA silencing blunted both its protective effects and the associated reduction in LECT2 expression.