Chrysin inhibits ferroptosis of cerebral ischemia/reperfusion injury via regulating HIF-1α/CP loop

Chrysin is a natural flavonoid with powerful neuroprotective capacity. Cerebral ischemia/reperfusion injury (CIRI) is associated with oxidative stress and ferroptosis. Hypoxia-inducible factor 1α (HIF-1α) and ceruloplasmin (CP) are the critical targets for oxidation reactions and iron transport. But the regulatory mechanism between them is still unclear. Transient middle cerebral artery occlusion (tMCAO) model in rats and oxygen and glucose deprivation/re-oxygenation (OGD/R) model in PC12 cells were applied. Pathological tissue staining and biochemical kit were used to evaluate the effect of chrysin. The relationship between HIF-1α and CP was verified by transcriptomics, qRT-PCR and Western blot. In CIRI, HIF-1α/CP loop was discovered to be the regulatory pathway of ferroptosis. CIRI led to activation and nuclear translocation of HIF-1α, which promoted CP transcription and translation, and downstream ferroptosis. Inhibition of HIF-1α had opposite effect on CP and ferroptosis regulation. Overexpression of CP increased the expression of HIF-1α, nevertheless, inhibited the nuclear translocation of HIF-1α and alleviated CIRI. Silencing CP promoted HIF-1α elevation in nucleus and aggravated CIRI. Mechanistically, chrysin restrained HIF-1α nuclear translocation, thereby inhibiting CP transcription and translation, which in turn reduced downstream HIF-1α expression and mitigated ferroptosis in CIRI. Our results highlight chrysin restrains ferroptosis in CIRI through HIF-1α/CP loop.

Solasonine ameliorates cerebral ischemia-reperfusion injury via suppressing TLR4/MyD88/NF-κB pathway and activating AMPK/Nrf2/HO-1 pathway

Solasonine (SS), the main active ingredient of Solanum nigrum L., has been reported to possess a variety of pharmacological properties. A recent study demonstrated a neuroprotective effect of SS in a mouse nerve injury model. However, its protective effects on cerebral ischemia/reperfusion injury (CIRI) remain to be elucidated. We investigated herein the in vitro and in vivo neuroprotective effects of SS. Primary hippocampal neurons were exposed to oxygen and glucose deprivation/reoxygenation (OGD/R) to construct an in vitro model while rats were treated with middle cerebral artery occlusion/reperfusion (MCAO/R) to establish an in vivo CIRI model. The results showed that SS reduced OGD/R-induced inflammatory responses of neurons by blocking secretion of TNF-α, IL-1β and IL-6. Moreover, SS ameliorated OGD/R-induced oxidative stress in neurons by decreasing the level of ROS and MDA and increasing the activity of SOD and GPx. We also found that SS protected neurons from OGD/R-induced apoptosis by down-regulating bax and cleaved caspase-3 and up-regulating bcl-2. The in vivo results revealed that SS administration reduced the infarct volume and alleviated the neurological deficit of MCAO/R rats as well as diminished neuronal damages in these rats. Our investigation on the underlying mechanisms indicated that the neuroprotective effect of SS on CIRI may be associated with the TLR4/MyD88/NF-κB and AMPK/Nrf2/HO-1 pathways. Taken together, these findings demonstrate that SS ameliorates CIRI via suppressing TLR4/MyD88/NF-κB pathway and activating AMPK/Nrf2/HO-1 pathway.

Orexin-A alleviates astrocytic apoptosis and inflammation via inhibiting OX1R-mediated NF-κB and MAPK signaling pathways in cerebral ischemia/reperfusion injury

Orexin-A (OXA) is a neuropeptide with neuroprotective effect by reducing cerebral ischemia/reperfusion injury (CIRI). Inflammation and apoptosis mediated by astrocyte activation are the key pathological mechanisms for CIRI. We thus attempted to confirm neuroprotective effects of OXA on astrocytic inflammation and apoptosis in CIRI and clarify the relative mechanisms. A middle cerebral artery occlusion and reperfusion (MCAO/R) rat model and U251 glioma cells model subjected to oxygen glucose deprivation and reperfusion (OGD/R) were established, with or without OXA treatment. Neurological deficit score was determined, and cerebral infarct volume was evaluated by 2,3,5-triphenyltetrazolium chloride (TTC) staining. Western Blot was used to detect the expressions of NF-κB p65, p-p65, p-ERK, p-p38, GFAP, OX1R, IL-1β, TNF-α, IL-6, iNOS, Bcl-2, Bax, CytC, cleaved caspase-9 and cleaved caspase-3 in vivo and in vitro. Pro-inflammatory cytokines in cell supernatant IL-1β, TNF-α and IL-6 were determined by ELISA. Hoechst 33342 staining was used to detect the apoptosis of astrocyte. Immunofluorescent staining was performed to assess the nuclear translocation of p65 and the expression of GFAP. The results showed that OXA significantly improved neurological deficit score and decreased the volume of infarct area in brain. OXA decreased inflammatory mediators, inhibited astrocyte activation and nuclear translocation of NF-κB and phosphorylation of NF-κB, MAPK/ERK and MAPK/p38. Besides, OXA suppressed apoptosis via upregulating the ratio of Bcl-2/Bax and downregulating cytochrome C, cleaved-caspase-9 and cleaved caspase-3. Overall, it was concluded that OXA exerts neuroprotective effect during CIRI through attenuating astrocytes apoptosis, astrocytes activation and pro-inflammatory cytokines production, by Inhibiting OX1R-mediated NF-κB, MAPK/ERK and MAPK/p38 signaling pathways. The progress in our study is helpful to elucidate the molecular mechanisms of OXA neuroprotection, which could lead to the development of new treatment strategies for ischemic stroke.

Effects of intermedin on autophagy in cerebral ischemia/reperfusion injury

OBJECTIVE

This study aimed to evaluate the effects of intermedin (IMD) on autophagy in cerebral ischemia/reperfusion (I/R) injury (CIRI).

METHODS

Sixty rats were randomly averaged into four groups: sham, ischemia/reperfusion (I/R), IMD, and 3-methyladenine (3-MA). In the sham group, the right common carotid artery, external carotid artery, and internal carotid artery were detached, and no monofilament was inserted. In the other groups, two hours after cerebral ischemia, the rats were injected through the lateral ventricle with normal saline for I/R group, IMD for the IMD group, and 3-MA for the 3-MA group for 24h. The cerebral injury was assessed by evaluation of neurological function, hematoxylin and eosin (H&E) staining, and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining. The expressions of autophagy associated proteins, such as microtubule-associated protein 1 light chain 3 (LC3), Beclin1, and sequestosome 1 (P62) were analyzed using immunohistochemistry staining and western blot. Meanwhile, transmission electron microscopy was used to investigate the ultrastructure of the brains.

RESULTS

IMD could reduce neuron cell damage and infarction formation and has a protective effect against CIRI as 3-MA. The levels of LC3II/LC3I and Beclin1 were significantly decreased and the P62 level was significantly higher in the IMD group compared with I/R group, which is similar to the effect of 3-MA on CIRI.

CONCLUSIONS

IMD has a similar effect as 3-MA, can reduce pathological neuronal injury and protect the brain against CIRI in rats by attenuating the effects of autophagy. Our findings provide evidence for IMD's protective effects in relation to ischemic cerebrovascular diseases.