Lipocalin-2 may produce damaging effect after cerebral ischemia by inducing astrocytes classical activation

Abstract

Background Functions of astrocytes in the rehabilitation after ischemic stroke, especially their impacts on inflammatory processes, remain controversial. This study uncovered two phenotypes of astrocytes, of which one was helpful, and the other harmful to anoxic neurons after brain ischemia. Methods We tested the levels of inflammatory factors including TNF-a, IL-6, IL-10, iNOS, IL-1beta, and CXCL10 in primary astrocytes at 0 h, 6 h, 12 h, 24 h, and 48 h after OGD, grouped the hypoxia astrocytes into iNOS-positive (iNOS(+)) and iNOS-negative (iNOS(−)) by magnetic bead sorting, and then co-cultured the two groups of cells with OGD-treated neurons for 24 h. We further verified the polarization of astrocytes in vivo by detecting the co-localization of iNOS, GFAP, and Iba-1 on MCAO brain sections. Lentivirus overexpressing LCN2 and LCN2 knockout mice (#024630. JAX, USA) were used to explore the role of LCN2 in the functional polarization of astrocytes. 7.0-T MRI scanning and the modified Neurological Severity Score (mNSS) were used to evaluate the neurological outcomes of the mice. Results After oxygen-glucose deprivation (OGD), iNOS mRNA expression increased to the peak at 6 h in primary astrocytes, but keep baseline expression in LCN2-knockout astrocytes. In mice with transient middle cerebral artery occlusion (tMCAO), LCN2 was proved necessary for astrocyte classical activation. In LCN2 knockout mice with MCAO, no classically activated astrocytes were detected, and smaller infarct volumes and better neurological functions were observed. Conclusions The results indicated a novel pattern of astrocyte activation after ischemic stroke and lipocalin-2 (LCN2) plays a key role in polarizing and activating astrocytes.

Lipocalin-2 Deficiency Reduces Oxidative Stress and Neuroinflammation and Results in Attenuation of Kainic Acid-Induced Hippocampal Cell Death

“…We also found that the ferritin and ceruloplasmin expressions in the hippocampi of KA-treated mice were reduced by LCN2 deletion. Nitric oxide, produced by iNOS, is known to cause neuronal damage and apoptotic cell death after KA administration [ 50 ], and LCN2 has been shown to produce a damaging effect after cerebral ischemia by inducing high iNOS expression in astrocytes both in vivo and in vitro [ 51 ]. Consistently, we found that iNOS expression increased in a time-dependent manner in KA-treated WT mice, but remained at baseline in LCN2 (−/−) mice.…”

WITHDRAWN: Combination of Paeoniflorin and Calycosin-7-glucoside Promotes Ischemic Stroke Recovery via the PI3K/AKT Signaling Pathway

“…A neurological behavior assessment was made according to previous methods 24 h after reperfusion. By mNSS scoring standards 20 , mild injury is scored 0 to 6 points, moderate injury 7 to 12 points, and severe injury 13 to 18 points. The mNSS score assessed was 18 points.…”

Genetic Deletion or Pharmacological Inhibition of Cyclooxygenase-2 Reduces Blood-Brain Barrier Damage in Experimental Ischemic Stroke

“…Consistent with these studies, we found that the levels of LCN2 increase dramatically in the stroked brain. Since both NE and LCN2 have been shown to mediate neuroinflammation and BBB damage in stroke (64)(65)(66)(67)(68), reduced levels of NE and LCN2 in COX-2 deficient animals could be a potential mechanism underlying the vasculoprotective effects of COX-2 blockade in stroke.…”