Sirtuin 5 aggravates microglia-induced neuroinflammation following ischaemic stroke by modulating the desuccinylation of Annexin-A1

Abstract

Background Microglia-induced excessive neuroinflammation plays a crucial role in the pathophysiology of multiple neurological diseases, such as ischaemic stroke. Controlling inflammatory responses is considered a promising therapeutic approach. Sirtuin 5 (SIRT5) mediates lysine desuccinylation, which is involved in various critical biological processes, but its role in ischaemic stroke remains poorly understood. This research systematically explored the function and potential mechanism of SIRT5 in microglia-induced neuroinflammation in ischaemic stroke. Methods Mice subjected to middle cerebral artery occlusion were established as the animal model, and primary cultured microglia treated with oxygen–glucose deprivation and reperfusion were established as the cell model of ischaemic stroke. SIRT5 short hairpin RNA, adenovirus and adeno-associated virus techniques were employed to modulate SIRT5 expression in microglia both in vitro and in vivo. Coimmunoprecipitation, western blot and quantitative real-time PCR assays were performed to reveal the molecular mechanism. Results In the current study, we showed that SIRT5 expression in microglia was increased in the early phase of ischaemic stroke. SIRT5 interacts with and desuccinylates Annexin A1 (ANXA1) at K166, which in turn decreases its SUMOylation level. Notably, the desuccinylation of ANXA1 blocks its membrane recruitment and extracellular secretion, resulting in the hyperactivation of microglia and excessive expression of proinflammatory cytokines and chemokines, ultimately leading to neuronal cell damage after ischaemic stroke. Further investigation showed that microglia-specific forced overexpression of SIRT5 worsened ischaemic brain injury, whereas downregulation of SIRT5 exhibited neuroprotective and cognitive-preserving effects against ischaemic brain injury, as proven by the decreased infarct area, reduced neurological deficit scores, and improved cognitive function. Conclusions Collectively, these data identify SIRT5 as a novel regulator of microglia-induced neuroinflammation and neuronal damage after cerebral ischaemia. Interventions targeting SIRT5 expression may represent a potential therapeutic target for ischaemic stroke.

A cell‐penetrating peptide exerts therapeutic effects against ischemic stroke by mediating the lysosomal degradation of sirtuin 5

“…First, we confirmed the cellular source and localization of SIRT5 and ANXA1 under physiological conditions and after MCAO. Consistent with our previous study, 15 double immunofluorescence staining of brain sections revealed that SIRT5 and ANXA1 were predominantly expressed in NeuN-positive neurons and Iba1-positive microglia, and an increase in SIRT5 and ANXA1 expression was observed in MCAO mice. However, there was rather poor colocalization of SIRT5 or ANXA1 with the astrocytic marker GFAP (Figures S1 and S2).…”

“…Unlike other SIRTs, SIRT5 possesses weak deacetylase activity but strong protein desuccinylase activity 12–14 . We previously reported that SIRT5 interacts with and desuccinylates annexin‐A1 (ANXA1) at lysine residue 166, promoting ANXA1 nuclear translocation and suppressing its membrane accumulation and secretion by microglia, which mediates the inflammatory response and eventually aggravates ischemic stroke injury 15 . In contrast, targeting abnormal SIRT5 has a neuroprotective effect against ischemic stroke.…”

“…In contrast, targeting abnormal SIRT5 has a neuroprotective effect against ischemic stroke. Actually, knockdown of SIRT5 using genetic manipulations, such as stereotaxic injection of antisense oligonucleotide or short hairpin RNA (shRNA), has been demonstrated to protect against neuronal damage in focal brain ischemia model mice 15 . However, the clinical applications of these methods into effective stroke treatment have been hampered by their limited ability to cross the blood‒brain barrier (BBB).…”

Emerging Roles of SIRT5 in Metabolism, Cancer, and SARS-CoV-2 Infection

“…Altogether, these factors contribute to neuronal injury. In line with this, SIRT5 KD in the microglia of middle cerebral artery occlusion (MCAO) mouse models exerted a protective role against cerebral ischemia/reperfusion injury [ 108 ].…”

“…Conversely, SIRT5 was shown to promote neuroinflammation and its expression was indicated to increase following ischemic stroke [ 108 ] . Mechanistically, SIRT5 desuccinylates annexin A1 (ANXA1) at Lys166, which in turn leads to a decrease in its SUMOylation.…”