Nitro-oleic acid-mediated blood-brain barrier protection reduces ischemic brain injury.

Nitro-oleic acid (OA-NO2), a nitroalkene formed in nitric oxide-dependent oxidative reactions, has been found in human plasma and is thought to regulate pathophysiological functions. Recently, accumulating evidence suggests that OA-NO2 may function as an anti-inflammatory mediator, and ameliorate the progression of diabetes and cardiovascular diseases. However, the role of OA-NO2 in ischemic brain injury remains unexplored. In this study, C57BL/6 mice were subjected to 1 h transient middle cerebral artery occlusion (MCAO) and followed by 1- 7 days of reperfusion. These mice were treated with vehicle, OA, or OA-NO2 (10 mg/kg) via tail vein injection at 2 h after the onset of MCAO. Our results show that intravenous administration of OA-NO2 led to reduced BBB leakage in ischemic brains, reduced brain infarct, and improved sensorimotor functions in response to ischemic insults when compared to OA and vehicle controls. Also, OA-NO2 significantly reduced BBB leakage-triggered infiltration of neutrophils and macrophages in the ischemic brains. Moreover, OA-NO2 treatment reduced the M1-type microglia and increased M2-type microglia. Mechanistically, OA-NO2 alleviated the decline of mRNA and protein level of major endothelial TJs including ZO-1 in stroke mice. Treatment of OA-NO2 also significantly inhibited stroke-induced inflammatory mediators, iNOS, E-selectin, P-selectin, and ICAM1, in mouse brains. In conclusion, OA-NO2 preserves BBB integrity and confers neurovascular protection in ischemic brain damage. OA-NO2-mediated brain protection may help us to develop a novel therapeutic strategy for the treatment of ischemic stroke.

The organic anion transporting polypeptide 1a5 is a pivotal transporter for the uptake of microcystin-LR by gonadotropin-releasing hormone neurons.

Microcystins (MCs) are widely distributed hepatotoxic polypeptides produced by cyanobacteria. Microcystin-LR (MC-LR) has the broadest distribution and strongest toxicity among more than 80 isoforms of hepatotoxic MCs. MC-LR suppresses the expression of gonadotropin-releasing hormone (GnRH) that is critically required for the release of testosterone, resulting in the induction of male reproductive toxicity. However, the specific mechanisms of the uptake of MC-LR by GnRH-secreting neurons still remain unclear. In this study, GT1-7 cells were exposed to MC-LR in order to determine whether the GnRH-secreting neurons were the target of MC-LR that could induce male reproductive toxicity. Our data demonstrated that at least four organic anion transporting polypeptides (Oatp1a4, Oatp1a5, Oatp5a1, Oatp2b1) were expressed in GnRH neurons at the mRNA level, but only Oatp1a5 was expressed at the protein level. Furthermore, we demonstrated that MC-LR could not be transported into Oatp1a5-deficient GT1-7 cells which were protected from cell viability loss induced by MC-LR. These data suggest that Oatp1a5 may play an important role in the toxic effect of MC-LR on GnRH neurons.