Critical Role of the Sphingolipid Pathway in Stroke: a Review of Current Utility and Potential Therapeutic Targets

Neuroprotection provided by isoflurane pre-conditioning and post-conditioning

Isoflurane, a volatile and inhalational anesthetic, has been extensively used in perioperative period for several decades. A large amount of experimental studies have indicated that isoflurane exhibits neuroprotective properties when it is administrated before or after (pre-conditioning and post-conditioning) neurodegenerative diseases (e.g., hypoxic ischemia, stroke and trauma). Multiple mechanisms are involved in isoflurane induced neuroprotection, including activation of glycine and γ-aminobutyric acid receptors, antagonism of ionic channels and alteration of the function and activity of other cellular proteins. Although neuroprotection provided by isoflurane is observed in many animal studies, convincing evidence is lacking in human trials. Therefore, there is still a long way to go before translating its neuroprotective properties into clinical practice.

Sphingosine 1-phosphate - A double edged sword in the brain

The physiological functions of sphingosine 1-phosphate (S1P) and its pathological roles in various diseases are increasingly being elucidated. Particularly, a growing body of literature has implicated S1P in the pathogenesis of brain related disorders. With the deciphering of more intricate aspects of S1P signalling, there is also a need to reconsider the notion of S1P only as a determinant of cell survival and proliferation. Further the concept of 'S1P-ceramide' balance as the controlling switch of cellular fate and functions needs to be refined. In this review, we focus on the brain related functions of S1P with special focus on its role in synaptic transmission, neuronal autophagy and neuroinflammation. The review also attempts to bring out the multi-faceted nature of S1P signalling aspects that makes it a 'double edged sword'. This article is part of a Special Issue entitled: Membrane Lipid Therapy: Drugs Targeting Biomembranes edited by Pablo V. Escribá.

Antiplatelet Strategies and Outcomes in Patients with Noncardioembolic Ischemic Stroke from a Real-World Study with a Five-Year Follow-Up

Aspirin and clopidogrel are both acceptable antiplatelet options for the secondary prevention of noncardioembolic ischemic stroke. Associations between Essen Stroke Risk Score (ESRS) and antiplatelet treatment in Chinese patients with noncardioembolic ischemic stroke were assessed. This retrospective study was taken in a tertiary care hospital located in eastern China. Patients with noncardioembolic ischemic stroke hospitalized during January 1, 2009, to December 31, 2011, were classified according to ESRS during index stroke hospitalization. Antiplatelet strategy at the time of discharge was categorized as aspirin (100 mg/day) vs. clopidogrel (75 mg/day). Patients received follow-up from July 1, 2014, to December 31, 2015, and the efficacy of clopidogrel and aspirin in different ESRS subgroups was assessed with respect to reducing the risk of a combined vascular event of recurrent stroke, myocardial infarction, or primary intracranial hemorrhage. Totally, 1175 non-cardiac stroke patients were included, among which 878 patients completed follow-up surveys. Of the patients who completed the follow-up, 458 (52.2%) had an ESRS > 3, and 621 (70.7%) received aspirin. Patients who received clopidogrel tended to be older, and more patients had hypertension, diabetes, and an ESRS > 3 than patients who received aspirin. Over a mean follow-up of 5.2 years, the rate of combined vascular events was 19.3% in the aspirin group and 16.7% in the clopidogrel group. Compared with clopidogrel-treated patients, a significant (P = 0.044) reduction in combined vascular events in aspirin-treated patients was observed in patients with an ESRS ≤ 3 (OR, odds ratio 0.5; 95% CI 0.3 to 0.9). However, a significant (P = 0.002) increase in combined vascular events was observed in patients with an ESRS > 3 (OR 2.2; 95% CI 1.3 to 3.8). More clopidogrel-treated patients with ESRS < 3 and ESRS = 3 discontinued treatment than their counterparts who took aspirin (P < 0.05). Adverse drug events, such as digestive discomfort and bleeding, were similar. In conclusion, clopidogrel is suggested for patients with an ESRS > 3 and aspirin for patients with an ESRS ≤ 3 for the secondary prevention of noncardioembolic ischemic stroke in Chinese patients.

Dimethyl Fumarate and Monomethyl Fumarate Promote Post-Ischemic Recovery in Mice

Oxidative stress plays an important role in cerebral ischemia-reperfusion injury. Dimethyl fumarate (DMF) and its primary metabolite monomethyl fumarate (MMF) are antioxidant agents that can activate the nuclear factor erythroid-2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) pathway and induce the expression of antioxidant proteins. Here, we evaluated the impact of DMF and MMF on ischemia-induced brain injury and whether the Nrf2 pathway mediates the effects provided by DMF and MMF in cerebral ischemia-reperfusion injury. Using a mouse model of transient focal brain ischemia, we show that DMF and MMF significantly reduce neurological deficits, infarct volume, brain edema, and cell death. Further, DMF and MMF suppress glial activation following brain ischemia. Importantly, the protection of DMF and MMF was mostly evident during the subacute stage and was abolished in Nrf2-/- mice, indicating that the Nrf2 pathway is required for the beneficial effects of DMF and MMF. Together, our data indicate that DMF and MMF have therapeutic potential in cerebral ischemia-reperfusion injury and their protective role is likely mediated by the Nrf2 pathway.