Rapid upregulation of matrix metalloproteinase 9 (MMP-9) leads to blood-brain barrier (BBB) breakdown following stroke, but no MMP-9 inhibitors have been approved in clinic largely due to their low specificities and side effects. Here, we explored the therapeutic potential of a human IgG monoclonal antibody (mAb), L13, which was recently developed with exclusive neutralizing specificity to MMP-9, nanomolar potency, and biological function, using mouse stroke models and stroke patient samples. We found that L13 treatment at the onset of reperfusion following cerebral ischemia or after intracranial hemorrhage (ICH) significantly reduced brain tissue injury and improved the neurological outcomes of mice. Compared to control IgG, L13 substantially attenuated BBB breakdown in both types of stroke model by inhibiting MMP-9 activity-mediated degradations of basement membrane and endothelial tight junction proteins. Importantly, these BBB-protective and neuroprotective effects of L13 in wild-type mice were comparable to Mmp9 genetic deletion and fully abolished in Mmp9 knockout mice, highlighting the in vivo target specificity of L13. Meanwhile, ex vivo co-incubation with L13 significantly neutralized the enzymatic activities of human MMP-9 in the sera of ischemic and hemorrhagic stroke patients, or in the peri-hematoma brain tissues from hemorrhagic stroke patients. Overall, we demonstrated that MMP-9 exclusive neutralizing mAbs constitute a potential feasible therapeutic approach for both ischemic and hemorrhagic stroke.

Intracerebral hemorrhage (ICH) remains a devastating type of stroke that lacks an effective treatment. Recent evidence has demonstrated that CCL2 is involved in the blood‐brain barrier (BBB) disruption and propagermanium (PG) as a CCL2 receptor inhibitor is neuroprotective in ischemic stroke. However, whether PG therapy exert effective role in acute ICH still unclear. In this study, our goal was to investigate the potential role of CCL2 and the effects of PG in ICH. Differentially expressed RNAs including CCL2 were detected in human ICH. CCL2 and the activation of p‐p38 MAPK and AQP4 expression were analyzed in rats after ICH. Brain water content and BBB integrity as well as neurological function were also examined after PG administration. In addition, the mechanism by which CCL2‐mediated BBB injury was further investigated by cell coculture. Our findings showed that PG could effectively reduce brain edema and improve neurobehavioral functions. p‐p38 MAPK and AQP4 expression were significantly inhibited by PG in vivo and in vitro. To the best of our knowledge, this is the first demonstration of PG in neuroprotecting the BBB integrity by inhibition of CCL2‐CCR2‐p38 MAPK pathway following ICH, targeting CCL2 could be developed as a novel treatment for hemorrhagic stroke.

Intracerebral hemorrhage (ICH) is a highly harmful neurological disorder with high rates of mortality, disability, and recurrence. However, effective therapies are not currently available. Secondary immune injury and cell death are the leading causes of brain injury and a poor prognosis. Pyroptosis is a recently discovered form of programmed cell death that differs from apoptosis and necrosis and is mediated by gasdermin proteins. Pyroptosis is caused by multiple pathways that eventually form pores in the cell membrane, facilitating the release of inflammatory substances and causing the cell to rupture and die. Pyroptosis occurs in neurons, glial cells, and endothelial cells after ICH. Furthermore, pyroptosis causes cell death and releases inflammatory factors such as interleukin (IL)-1β and IL-18, leading to a secondary immune-inflammatory response and further brain damage. The NOD-like receptor protein 3 (NLRP3)/caspase-1/gasdermin D (GSDMD) pathway plays the most critical role in pyroptosis after ICH. Pyroptosis can be inhibited by directly targeting NLRP3 or its upstream molecules, or directly interfering with caspase-1 expression and GSDMD formation, thus significantly improving the prognosis of ICH. The present review discusses key pathological pathways and regulatory mechanisms of pyroptosis after ICH and suggests possible intervention strategies to mitigate pyroptosis and brain dysfunction after ICH.

Disruption of the blood-brain barrier (BBB) and subsequent neurological deficits are the most severe consequence of intracerebral hemorrhage (ICH). Minocycline has been wildly used clinically as a neurological protective agent in clinical practice. However, the underlying mechanisms by which minocycline functions remain unclear. Therefore, we assessed the influence of minocycline on BBB structure, neurological function, and inflammatory responses in a collagenase-induced ICH model, and elucidated underlying molecular mechanisms as well. Following a single injection of collagenase VII-S into the basal ganglia, BBB integrity was assessed by Evans blue extravasation while neurological function was assessed using an established neurologic function scoring system. Minocycline treatment significantly alleviated the severity of BBB disruption, brain edema, and neurological deficits in ICH model. Moreover, minocycline decreased the production of inflammatory mediators including TNF, IL-6, and MMP-9, by microglia. Minocycline treatment decreased DKK1 expression but increased Wnt1, β-catenin and Occludin, a phenomenon mimicked by DKK1 silencing. These data suggest that minocycline improves the consequences of ICH by preserving BBB integrity and attenuating neurologic deficits in a DKK1-related manner that involves enhancement of the Wnt1-β-catenin activity.

Background: Intracerebral hemorrhage (ICH) is a catastrophic cerebrovascular disease with high morbidity and mortality. Evidence demonstrated that sphingosine‐1‐phosphate receptor (S1PR) plays a vital role in inflammatory damage via the upregulation of CCL2 expression. However, whether S1PR3 is involved in blood‐brain barrier (BBB) breakdown via CCL2 activation after ICH has not been described.Methods: We investigated the expression profiles of all S1PRs using high‐throughput RNA‐seq analysis and RT‐PCR. The potential role of S1PR3 and interaction between S1PR3 and CCL2 were evaluated via Western blotting, immunofluorescence, and flow cytometry. BBB disruption was examined via magnetic resonance imaging, transmission electron microscopy, and Evans blue extravasation. Microglial activation, proliferation, and polarization were assessed via histopathological analysis. The expression levels of CCL2, p‐p38 MAPK, ICAM‐1, and ZO‐1 were examined in vitro and in vivo.Results: The present results showed that the levels of S1PR3 and its ligand, sphingosine 1‐phosphate (S1P), were dramatically increased following ICH, which regulated the expression of CCL2 and p38MAPK. Moreover, reductions in brain edema volume, amelioration of BBB integrity, and improvements in behavioral deficits were achieved after the administration of CAY10444, an S1PR3 antagonist, to rats. Remarkably increased CCL2, p‐p38MAPK, and ICAM‐1 expression and decreased ZO‐1 expression were observed in cocultured human astrocytes (HAs) and hCMEC/D3 cells after S1P stimulation. However, the expression levels of CCL2, p‐p38 MAPK, and ICAM‐1 were decreased and ZO‐1 expression was increased after S1PR3 inhibition. In addition, microglial proliferation and M1 polarization were attenuated after CAY10444 administration.Conclusion: To the best of our knowledge, this is the first demonstration of the neuroprotective role of S1PR3 modulation in maintaining BBB integrity by inhibiting the S1PR3‐CCL2 axis after ICH, providing a novel treatment for ICH by targeting S1PR3.