Jingrui Pan

Remote ischemic conditioning for acute ischemic stroke: dawn in the darkness.

Abstract Stroke is a leading cause of disability with high morbidity and mortality worldwide. Of all strokes, 87% are ischemic. The only approved treatments for acute ischemic stroke are intravenous thrombolysis with alteplase within 4.5 h and thrombectomy within 8 h after symptom onset, which can be applied to just a few patients. During the past decades, ischemic preconditioning has been widely studied to confirm its neuroprotection against subsequent ischemia/reperfusion injury in the brain, including preconditioning in situ or in a remote organ (such as a limb) before onset of brain ischemia, the latter of which is termed as remote ischemic preconditioning. Because acute stroke is unpredicted, ischemic preconditioning is actually not suitable for clinical application. So remote ischemic conditioning performed during or after the ischemic duration of the brain was then designed to study its neuroprotection alone or in combination with alteplase in animals and patients, which is named as remote ischemic perconditioning or remote ischemic postconditioning. As expected, animal experiments and clinical trials both showed exciting results, indicating that an evolution in the treatment for acute ischemic stroke may not be far away. However, some problems or disputes still exist. This review summarizes the research progress and unresolved issues of remote ischemic conditioning (pre-, per-, and post-conditioning) in treating acute ischemic stroke, with the hope of advancing our understanding of this promising neuroprotective strategy for ischemic stroke in the near future.

Temporal pattern of Toll-like receptor 9 upregulation in neurons and glial cells following cerebral ischemia reperfusion in mice

Purpose: The family of Toll-like receptors (TLRs) has recently been reported to play a role in ischemic injury, but the time course and cell types of the post-stroke TLR9 upregulation remain unclear. In this study, we investigated the dynamic changes of TLR9 expression and the expression of TLR9 in neurons and glial cells after cerebral ischemia reperfusion in mice. Methods: Focal cerebral ischemia was induced by middle cerebral artery occlusion for 90 min in male C57BL/6 mice. The TLR9 expression levels in the tissue surrounding the infarct were detected by Western Blot at 6 h, 3 d, 7 d, 14 d, 21 d, and 28 d after reperfusion. The expression of TLR9 in neurons and glial cells was observed by immunofluorescence staining. Results: The expression of TLR9 protein first increased and then decreased, with the peak observed at 14 d–21 d. Only small punctate intracellular TLR9 was occasionally observed in the neurons at each time point, and the TLR9-positive rate showed no difference at different time points. By contrast, the activated microglia gathered at the margin of the infarct, and the intracellular TLR9 changed from scattered small punctate to coarse and lumpy. The TLR9-positive rate of microglia was first increased and then decreased with time, with the peak observed at 3 d. No positive TLR9 staining was found in the astrocytes and oligodendrocytes. Conclusions: TLR9 expression showed dynamic changes for a long period of time and microglias were the main brain cells to express TLR9 after cerebral ischemia and reperfusion.

Relationship between activated astrocytes and hypoxic cerebral tissue in a rat model of cerebral ischemia/reperfusion.

Following cerebral infarction, hypoxic tissues remains in the ischemic cortex for long periods of time. Glial fibrillary acidic protein (GFAP) is a specific marker of astrocytes, which is thought to be essential for neuronal survival. We aimed to clarify the relationship between hypoxic tissue and astrocytes following cerebral infarction. Rats with middle cerebral artery occlusion were randomly divided into a 1.5-hour ischemia-reperfusion(1.5-hour IR) group and a permanent ischemia (PI) group. Hypoxic tissue and GFAP fluorescence intensity in the ischemic cortex were observed postoperatively on days 1, 3, 7, and 14. Results showed that hypoxic tissue was present from day 1 to 14 in the 1.5-hour IR group and on days 1 and 3 in the PI group. The GFAP fluorescence intensity in the 1.5-hour IR group was stronger than that in the PI group at the same time point of observation. Over time, GFAP expression increased and peaked at 7 days in each group, followed by a decrease in signal. In hypoxic tissue, the GFAP fluorescence intensity was stronger than that in the surrounding tissue at all observation time points. These data indicate that astrocytes were strongly activated in hypoxic tissue induced by temporary ischemia followed by reperfusion. The activation of astrocytes may partially contribute to the survival and repair of hypoxic tissue following brain ischemia.

Band engineering and periodic defects doping by lattices compounding.

Our numerical simulation results demonstrate that 2D lattices compounding can create either a broad single complete photonic band gap or both first and second order complete band gaps. The results also show that photonic band gap properties are dependent on both the parameters of the single lattices and the relative position of the two compound lattices. Furthermore, if a compound structure is composed of two sets of lattices, the one with a larger periodic constant (a2) will serve as defects. While the defect modes are direction independent as a2 > 5 a, they are direction dependent as a2 < 5 a. Moreover, by optimizing of the rod size of the lattice with a2, many kinds of defect modes can be obtained to satisfy the different applications. The transmitted spectra and reflected spectra of this kind of structures demonstrate that the transmittances of the defect modes are dependent a2.

The TLR9 Antagonist iCpG-ODN at Different Dosages Inhibits Cerebral Ischemia/Reperfusion Injury in Mice.

BACKGROUND Inflammatory responses are important mechanisms that are involved in cerebral ischemia/reperfusion(I/R) injury. Whether toll-like receptor 9(TLR9), which belongs to the innate immune system, takes part in the inflammatory responses following cerebral I/R remains unclear. METHOD This study examined the effect of different dosages of the TLR9 antagonist inhibitory oligodeoxynucleotide (iCpG-ODN) on cerebral I/R injury by using a mouse model of transient middle cerebral artery occlusion. Neurological function, infarct size, splenocytes and the expression of TLR9 and the downstream products of the TLR9 pathways were determined after cerebral I/R for up to 72 hours. RESULTS The Clarks focal symptom scoring showed iCpG-ODN improved neurological deficits following focal cerebral I/R. The iCpG-ODN administration significantly decreased the infarct size in a dose-dependent manner. RT-PCR showed that iCpG-ODN attenuated the I/R-induced RNA expression of TLR9. Immunoblot showed that iCpG-ODN prevented I/R-induced increases in NFκB and IRF7 levels and that it further downregulated the levels of IL-1β, TNF-α, and INF-β in the brain. iCpG-ODN did not alter the levels of TNF-α or INF-β in the peripheral blood or affect stroke-induced changes in the number of splenocytes. CONCLUSION These findings suggest that iCpG-ODN induced protection against cerebral I/R via inhibiting inflammatory responses in a dose-dependent manner and may be useful in therapy for stroke patients.

The association between family factors and child behaviour problems using dyadic data

BACKGROUND Parental psychopathology and family issues are key influence factors to child behaviour problems. This study aimed to investigate the dyadic impact of maternal and paternal depression and perceived family functioning on child behaviour problems. METHODS Both maternal and paternal depression, perceived family functioning and reported child behaviour problems were collected, respectively. Because of the interdependent characteristic of dyadic data, structural equation modelling was used to examine the relationship among all variables and the mutual influence between mother and father. RESULTS Results showed that father-perceived family functioning mediated the relationship between parental depression and child behaviour problems, but mother-perceived family functioning did not show this mediation effect. Meanwhile, maternal and paternal depression influenced both of their own and their partners perceived family functioning. CONCLUSIONS The findings indicated that paternal psychopathology and family functioning should not be overlooked in child behaviour development. In addition, this study underscored the importance to investigate the different impact of father and mother on child development within a dyadic unit.

The Possibility and Molecular Mechanisms of Cell Pyroptosis After Cerebral Ischemia

Stroke is an important disease that is prevalent worldwide [1–3]. Ischemic stroke accounts for 80% of stroke cases. Currently, evidence-based effective treatments for ischemic stroke are limited, and only intravenous thrombolysis with Alteplase (a commercially available thrombolytic agent) within 4.5 h of stroke onset and thrombectomy and arterial thrombolysis within 6–24 h of onset are effective [4, 5]. However, because these two treatments have strict indications and certain risks (reperfusion injury and bleeding) [5–8], there is an urgent need to develop new treatment methods. Thus, comprehensive elucidation of the molecular mechanisms underlying ischemic brain damage and the search for key signaling pathways and protein molecules are important for guiding the clinical treatment of ischemic stroke. The inflammatory reaction is an important pathophysiological mechanism underlying cerebral ischemic injury. The inflammatory reaction after cerebral ischemia influences the development of ischemic injury and is considered to be a key element related to lesion progression. Both permanent ischemia and reperfusion after transient ischemia have been shown to induce inflammatory reactions in cerebral tissues [9]. However, the pathophysiological processes of these two ischemic conditions are different [10], and the severity of the inflammatory reactions also differ. An inflammatory reaction can be initiated within several hours of stroke onset and can last for several days or even longer [11]. Therefore, treatments targeting the inflammatory reactions have a longer time window and excellent prospects for clinical application. Cells in the ischemic core undergo necrosis within a short time after cerebral artery occlusion, whereas cells in the surrounding area (ischemic penumbra) can survive for several hours [12]. Restoration of blood flow within this time window may allow cells to survive but may also result in irreversible cell death (reperfusion injury) [12]. For several minutes to several hours during cerebral ischemia, dead cells release danger signals, such as purines, high mobility group box 1 protein, heat shock proteins, and peroxiredoxin family proteins [13]. These danger signals bind to the receptors in the cell membrane or intracellular receptors of adjacent cells to initiate innate immune responses, resulting in inflammatory reactions [13]. These endogenous danger signaling molecules are known as damage-associated molecular patterns (DAMPs). The receptors that recognize DAMPs are known as pattern recognition receptors (PRRs) and mainly include families such as the Toll-like receptors and Nod-like receptors (NLRs) [14]. DAMPs released by necrotic cells in the ischemic core are the source of signals that initiate inflammatory reactions. However, the sources of the danger signals that promote further development of the inflammatory reactions and how they exert their functions are still unclear. Cells in the ischemic penumbra are thought to undergo apoptosis, which can last for several weeks [15]. Zhaofei Dong and Kuang Pan have contributed equally to this work.

Mitochondrial dysfunction induces NLRP3 inflammasome activation during cerebral ischemia/reperfusion injury

BackgroundNod-like receptor protein 3 (NLRP3) inflammasome is a crucial factor in mediating inflammatory responses after cerebral ischemia/reperfusion (I/R), but the cellular location of NLRP3 inflammasome in cerebral I/R has yet come to a conclusion, and there is still no specific evidence to state the relationship between mitochondria and the NLRP3 inflammasome in cerebral I/R.MethodsIn the present study, we detected the cellular localization of NLRP3 inflammasomes in a transient middle cerebral artery occlusion (tMCAO) rat model and a transwell co-culture cell system under oxygen-glucose deprivation/reoxygenation (OGD/R) conditions. Then, we investigated the relationship between mitochondrial dysfunction and the activation of NLRP3 inflammasomes in different cell types after OGD/R and cerebral I/R injury.ResultsOur results showed that NLRP3 inflammasomes were first activated in microglia soon after cerebral I/R injury onset and then were expressed in neurons and microvascular endothelial cells later, but they were mainly in neurons. Furthermore, mitochondrial dysfunction played an important role in activating NLRP3 inflammasomes in microglia after OGD/R, and mitochondrial protector could inhibit the activation of NLRP3 inflammasomes in cerebral I/R rats.ConclusionOur findings may provide novel insights into the cell type-dependent activation of NLRP3 inflammasomes at different stages of cerebral I/R injury and the role of mitochondrial dysfunction in activating the NLRP3 inflammasome pathway.

Hydroxysafflor Yellow A Reprograms TLR9 Signalling Pathway in Ischaemic Cortex after Cerebral Ischaemia and Reperfusion

BACKGROUND AND OBJECTIVE Hydroxysafflor yellow A (HSYA) was reported to suppress inflammation in ischaemic microglia. However, the mechanism through which HSYA inhibits inflammation caused by cerebral ischaemia and reperfusion injury remains unknown. Here, we have mimicked acute cerebral ischaemia and reperfusion injury by subjecting male Sprague-Dawley rats to transient middle cerebral artery occlusion for 90 minutes and have demonstrated that toll-like receptor 9 (TLR9) was upregulated from day 3 after reperfusion, accompanied by the persistent activation of the pro-inflammatory nuclear factor-κB (NF-κB) pathway from 6 hours to day 7. HSYA was injected intraperitoneally at a dose of 6 mg/kg per day, which activated TLR9 in microglia of ischaemic cortex at 6 hours after reperfusion and then obviously suppressed the NF-κB pathway from day 1 to day 7. Meanwhile, HSYA also activated the anti-inflammatory pathway through interferon regulatory factor 3 from day 1 to day 3. The anti-inflammatory effect of HSYA was partially reversed by TLR9-siRNA interference in primary microglia, which was stimulated by oxygen-glucose deprivation and reoxygenation treatment. The regulation of TLR9-mediated inflammation by HSYA was consistent with the recovery of neurological deficits in rats. CONCLUSION Therefore, our findings support that HSYA exerts anti-inflammatory effects by reprogramming the TLR9 signalling pathway during treatment of acute cerebral ischaemia and reperfusion injury.