IL-17A Neutralization Improves the Neurological Outcome of Mice With Ischemic Stroke and Inhibits Caspase-12-Dependent Apoptosis

IL-17A exacerbates caspase-12-dependent neuronal apoptosis following ischemia through the Src-PLCγ-calpain pathway

Interleukin-17 A (IL-17 A) contributes to inflammation and causes secondary injury in post-stroke patients. However, little is known regarding the mechanisms that IL-17 A is implicated in the processes of neuronal death during ischemia. In this study, the mouse models of middle cerebral artery occlusion/reperfusion (MCAO/R)-induced ischemic stroke and oxygen-glucose deprivation/reoxygenation (OGD/R)-simulated in vitro ischemia in neurons were employed to explore the role of IL-17 A in promoting neuronal apoptosis. Mechanistically, endoplasmic reticulum stress (ERS)-induced neuronal apoptosis was accelerated by IL-17 A activation through the caspase-12-dependent pathway. Blocking calpain or phospholipase Cγ (PLCγ) inhibited IL-17 A-mediated neuronal apoptosis under ERS by inhibiting caspase-12 cleavage. Src and IL-17 A are linked, and PLCγ directly binds to activated Src. This binding causes intracellular Ca2+ flux and activates the calpain-caspase-12 cascade in neurons. The neurological scores showed that intracerebroventricular (ICV) injection of an IL-17 A neutralizing mAb decreased the severity of I/R-induced brain injury and suppressed apoptosis in MCAO mice. Our findings reveal that IL-17 A increases caspase-12-mediated neuronal apoptosis, and IL-17 A suppression may have therapeutic potential for ischemic stroke.

Activin A alleviates neuronal injury through inhibiting cGAS-STING-mediated autophagy in mice with ischemic stroke

Activin A plays an essential role in ischemic stroke as a well-known neuroprotective factor. We previously reported that Activin A could promote white matter remyelination. However, the exact molecular mechanism of Activin A in neuronal protection post-stroke is still unclear. In this study, the middle cerebral artery occlusion/reperfusion (MCAO/R)-induced ischemic stroke mouse model and oxygen-glucose deprivation/reoxygenation (OGD/R)-treated primary neurons were used to explore the molecular mechanism of Activin A-mediated neuroprotection against ischemic injuries. We found that Activin A significantly inhibits cGAS-STING-mediated excessive autophagy through the PI3K-PKB pathway, but not mTOR-dependent autophagy. Consequently, Activin A protected neurons against OGD/R-induced ischemic injury and improved cell survival in a dose-dependent manner. In addition, Activin A improved neurological functions and reduced infarct size of mice with MCAO/R-induced ischemic stroke by inhibiting autophagy. Furthermore, Activin A depended on ACVR1C receptor to exert neuroprotective effects in 1 h MCAO/R treated mice. Our findings showed that Activin A alleviated neuronal ischemic injury through inhibiting cGAS-STING-mediated excessive autophagy in mice with ischemic stroke, which may suggest a potential therapeutic target for ischemic stroke.

Oridonin ameliorates caspase-9-mediated brain neuronal apoptosis in mouse with ischemic stroke by inhibiting RIPK3-mediated mitophagy

Neuronal loss is a primary factor in determining the outcome of ischemic stroke. Oridonin (Ori), a natural diterpenoid compound extracted from the Chinese herb Rabdosia rubescens, has been shown to exert anti-inflammatory and neuroregulatory effects in various models of neurological diseases. In this study we investigated whether Ori exerted a protective effect against reperfusion injury-induced neuronal loss and the underlying mechanisms. Mice were subjected to transient middle cerebral artery occlusion (tMCAO), and were injected with Ori (5, 10, 20 mg/kg, i.p.) at the beginning of reperfusion. We showed that Ori treatment rescued neuronal loss in a dose-dependent manner by specifically inhibiting caspase-9-mediated neuronal apoptosis and exerted neuroprotective effects against reperfusion injury. Furthermore, we found that Ori treatment reversed neuronal mitochondrial damage and loss after reperfusion injury. In N2a cells and primary neurons, Ori (1, 3, 6 μM) exerted similar protective effects against oxygen-glucose deprivation and reoxygenation (OGD/R)-induced injury. We then conducted an RNA-sequencing assay of the ipsilateral brain tissue of tMCAO mice, and identified receptor-interacting protein kinase-3 (RIPK3) as the most significantly changed apoptosis-associated gene. In N2a cells after OGD/R and in the ipsilateral brain region, we found that RIPK3 mediated excessive neuronal mitophagy by activating AMPK mitophagy signaling, which was inhibited by Ori or 3-MA. Using in vitro and in vivo RIPK3 knockdown models, we demonstrated that the anti-apoptotic and neuroprotective effects of Ori were RIPK3-dependent. Collectively, our results show that Ori effectively inhibits RIPK3-induced excessive mitophagy and thereby rescues the neuronal loss in the early stage of ischemic stroke.

Role of IL-17A in different stages of ischemic stroke

Interleukin-17A (IL-17A) plays an important role in the progression of ischemic stroke. IL-17A mediates the endothelial inflammatory response, promotes water and sodium retention, and changes the electrophysiological structure of the atrium, accelerating the progression of ischemic stroke risk factors such as atherosclerotic plaques, hypertension, and atrial fibrillation. In the acute phase of ischemic stroke, IL-17A mediates neuronal injury through neutrophil chemotaxis to the site of injury, the induction of neuronal apoptosis, and activation of the calpain-TRPC-6 (transient receptor potential channel-6) pathway. During ischemic stroke recovery, IL-17A, which is mainly derived from reactive astrocytes, promotes and maintains the survival of neural precursor cells (NPCs) in the subventricular zone (SVZ), neuronal differentiation, and synapse formation and participates in the repair of neurological function. Therapies targeting IL-17A-associated inflammatory signaling pathways can reduce the risk of ischemic stroke and neuronal damage and are a new therapeutic strategy for ischemic stroke and its risk factors. In this paper, we will briefly discuss the pathophysiological role of IL-17A in ischemic stroke risk factors, acute and chronic inflammatory responses, and the potential therapeutic value of targeting IL-17A.

The longitudinal changes of serum JKAP and IL-17A, and their linkage with anxiety, depression, and cognitive impairment in acute ischemic stroke patients

BACKGROUND

Our previous study discovers that Jun N-terminal kinase pathway-associated phosphatase (JKAP) is dysregulated and negatively links with the disease severity in acute ischemic stroke (AIS) patients. This study intended to further evaluate the linkage of JKAP and interleukin (IL)-17A with anxiety, depression, and cognitive impairment in AIS patients.

METHODS

Serum JKAP and IL-17A levels in 120 AIS patients at admission, 1st (D1), 3rd (D3), 7th (D7) day after admission, and from 20 controls, were detected by ELISA. Hospital Anxiety and Depression Scale (HADS) and Mini-Mental State Examination (MMSE) were assessed in AIS patients at discharge.

RESULTS

JKAP (p < 0.001) was reduced, but IL-17A (p < 0.001) was increased in AIS patients versus controls, and negatively correlated with each other in AIS patients (p = 0.014). In AIS patients, JKAP was reduced from baseline to D1 and then increased to D7 (p < 0.001), while IL-17A exhibited an opposite trend (p < 0.001). Notably, JKAP at D3 was negatively linked with HADS-anxiety score (p = 0.044), then decreased JKAP at D3 (p = 0.017) and D7 (p = 0.037) related to increased anxiety occurrence. However, JKAP was not linked to HADS-depression score or depression occurrence. Besides, JKAP at multiple time points were positively associated with MMSE score (all p < 0.05); decreased JKAP at D3 (p = 0.017) and D7 (p = 0.026) related to raised cognitive impairment occurrence.

CONCLUSION

JKAP initially decreases then shows an increasing trend after disease onset, and its decrement relates to elevated IL-17A, anxiety and cognitive impairment in AIS patients.

EphA4 regulates white matter remyelination after ischemic stroke through Ephexin-1/RhoA/ROCK signaling pathway

Ischemic stroke, which accounts for nearly 80% of all strokes, leads to white matter injury and neurobehavioral dysfunction, but relevant therapies to inhibit demyelination or promote remyelination after white matter injury are still unavailable. In this study, the middle cerebral artery occlusion/reperfusion (MCAO/R) in vivo and oxygen-glucose deprivation/reoxygenation (OGD/R) in vitro were used to establish the ischemic models. We found that Eph receptor A4 (EphA4) had no effect on the apoptosis of oligodendrocytes using TUNEL staining. In contrast, EphA4 promoted proliferation of oligodendrocyte precursor cells (OPCs), but reduced the numbers of mature oligodendrocytes and the levels of myelin-associated proteins (MAG, MOG, and MBP) in the process of remyelination in ischemic models in vivo and in vitro as determined using PDGFRα-EphA4-shRNA and LV-EphA4 treatments. Notably, conditional knockout of EphA4 in OPCs (EphA4^fl/fl  + AAV-PDGFRα-Cre) improved the levels of myelin-associated proteins and functional recovery following ischemic stroke. In addition, regulation of remyelination by EphA4 was mediated by the Ephexin-1/RhoA/ROCK signaling pathway. Therefore, EphA4 did not affect oligodendrocyte (OL) apoptosis but regulated white matter remyelination after ischemic stroke through the Ephexin-1/RhoA/ROCK signaling pathway. EphA4 may provide a novel and effective therapeutic target in clinical practice of ischemic stroke.

P300 Inhibition Improves Cell Apoptosis and Cognition Impairment Induced by Sevoflurane Through Regulating IL-17A Activation

BACKGROUND

Sevoflurane (Sev) is a rapidly acting, potent inhalation anesthetic with rapid uptake and elimination. But many studies have shown that Sev could result in cognition dysfunction in adolescent or aging patients. Now, therapeutic targeting with IL-17A antibody has shown a promising effect on Sev-induced cognition impairment. In the study we report that P300 inhibition could act as an alternative approach to decrease IL-17A activity.

METHODS

SHSY5Y cells were treated with Sev and cell apoptosis was evaluated by Annexin V-FITC/PI staining. The expression of P300 and IL-17A were assessed by Western blotting. Water maze tests were conducted in order to assess the cognitive function.

RESULTS

We found that P300 and IL-17A were activated in SHSY5Y cells treated with Sev. P300 inhibitor C646 could reduce the apoptosis induced by Sev through decreasing IL-17A avtivity. Furthermore, IL-17A expression was upregulated after neurons were transfected with P300 expression plasmid and IL-17A expression was downregulated after neurons were incubated with P300 inhibitor C646. P300 overexpression could upregulate the promoter activity of IL-17A. Finally, in a rat model treated with Sev, we also found C646 to significantly improve the cognition impairment through the IL-17A pathway.

CONCLUSIONS

These data show that P300 will potentially be a new drug target for the therapy of cognition impairment caused by Sev.