Abstract
BackgroundThe role of the immune system in stroke is well-recognised. Fingolimod, an immunomodulatory agent licensed for the management of relapsing-remitting multiple sclerosis, has been shown to provide benefit in rodent models of stroke. Its mechanism of action, however, remains unclear. We hypothesised fingolimod increases the number and/or function of regulatory T cells (Treg), a lymphocyte population which promotes stroke recovery. The primary aim of this study was to rigorously investigate the effect of fingolimod on Tregs in a mouse model of brain ischaemia. The effect of fingolimod in mice with common stroke-related comorbidities (ageing and hypercholesteremia) was also investigated.MethodsYoung (15–17 weeks), aged C57BL/6 mice (72–73 weeks), and ApoE−/− mice fed a high-fat diet (20–21 weeks) underwent permanent electrocoagulation of the left middle cerebral artery. Mice received either saline or fingolimod (0.5 mg/kg or 1 mg/kg) at 2, 24, and 48 h post-ischaemia via intraperitoneal injection. Another cohort of young mice (8–9, 17–19 weeks) received short-term (5 days) or long-term (10 days) fingolimod (0.5 mg/kg) treatment. Flow cytometry was used to quantify Tregs in blood, spleen, and lymph nodes. Immunohistochemistry was used to quantify FoxP3+ cell infiltration into the ischaemic brain.ResultsFingolimod significantly increased the frequency of Tregs within the CD4+ T cell population in blood and spleen post-ischaemia in all three mouse cohorts compared to untreated ischemic mice. The highest splenic Treg frequency in fingolimod-treated mice was observed in ApoE−/− mice (9.32 ± 1.73% vs. 7.8 ± 3.01% in young, 6.09 ± 1.64% in aged mice). The highest circulating Treg frequency was also noted in ApoE−/− mice (8.39 ± 3.26% vs. 5.43 ± 2.74% in young, 4.56 ± 1.60% in aged mice). Fingolimod significantly increased the number of FoxP3+ cells in the infarct core of all mice. The most pronounced effects were seen when mice were treated for 10 days post-ischaemia.ConclusionsFingolimod increases Treg frequency in spleen and blood post-ischaemia and enhances the number of FoxP3+ cells in the ischaemic brain. The effect of fingolimod on this regulatory cell population may underlie its neuroprotective activity and could be exploited as part of future stroke therapy.
Highlights
The role of the immune system in stroke is well-recognised
Fingolimod is effective in an acute or subacute setting, and promotes repair in rodents when administered as late as 24 h post-ischaemia [9].With increasing prevalence and effectiveness of reperfusion therapy, and considering that fingolimod is effective against ischemia-reperfusion injury in various organs, the neuroprotective effect of fingolimod could synergize with the effect of increased blood flow to the infarct site [10, 11]
Only the higher dose (1 mg/kg) produced a significant response (p = 0.0150). This increase was only recorded in young mice. These results demonstrate that fingolimod treatment significantly increases the frequency of CD4+ CD25+forkhead box P3 (FoxP3)+ Treg cells in the periphery of all three cohorts under study
Summary
The role of the immune system in stroke is well-recognised. Fingolimod, an immunomodulatory agent licensed for the management of relapsing-remitting multiple sclerosis, has been shown to provide benefit in rodent models of stroke. The primary aim of this study was to rigorously investigate the effect of fingolimod on Tregs in a mouse model of brain ischaemia. Fingolimod has proven effective in various rodent models of stroke, including both transient and permanent focal ischaemia [7]. Fingolimod is effective in an acute or subacute setting, and promotes repair in rodents when administered as late as 24 h post-ischaemia [9].With increasing prevalence and effectiveness of reperfusion therapy, and considering that fingolimod is effective against ischemia-reperfusion injury in various organs, the neuroprotective effect of fingolimod could synergize with the effect of increased blood flow to the infarct site [10, 11]. While considerable evidence supports the future use of fingolimod in stroke therapy, the exact mechanism of action remains unclear, immunomodulation is likely to be involved [15]
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have