Therapeutic Potential of PCSK9 Inhibitors in Regulating Neuroinflammation in Acute Ischemic Stroke

Acute ischemic stroke (AIS) poses a substantial risk of permanent disability and death globally, with neuroinflammation being a key driver of secondary brain damage post-stroke. Proprotein convertase subtilisin/kexin type 9 (PCSK9), beyond its well-accepted role in cholesterol metabolism through low-density lipoprotein receptor (LDLR) degradation, has emerged as an important mediator of neuroinflammation, making it an attractive new therapeutic target. This has sparked broader discussions about the potential pleiotropic effects of PCSK9 inhibitors on brain function. Proprotein convertase subtilisin/kexin type 9 mediates inflammation post-ischemia directly and indirectly by disrupting mTOR pathways. This stimulates signaling cascades associated with inflammation. For example, the nuclear factor-κB (NF-κB), toll-like receptor 4 (TLR4), and mitogen-activated protein kinase (MAPK) pathways in microglia activation. It also brings about reaction in astrocytes and increases the release of cytokines like interleukin-1β, interleukin-6, and tumor necrosis factor-α. Proprotein convertase subtilisin/kexin type 9 interacts with apolipoprotein E receptor 2 (ApoER2) present on neurons cells, leading to further inflammatory effects. Proprotein convertase subtilisin/kexin type 9 indirectly increases lipoprotein(a) [Lp(a)], which promotes inflammation through the Lp(a)-TLR4 axis and induces endothelial dysfunction. Monoclonal antibodies (evolocumab, alirocumab) and small interfering RNA (siRNA) agents (inclisiran) are examples of PCSK9 inhibitors. According to preclinical studies, these inhibitors can mitigate neuroinflammation by blocking the M1 polarization of microglia and downregulating key pro-inflammatory factors while preserving the blood-brain barrier (BBB). They also inhibit neuronal apoptosis via the Bcl-2/Bax-caspase cascade and reduce the aggregation of β-amyloid (Aβ). Evidently, the findings from cardiac ischemia-reperfusion models show that pretreatment with PCSK9 inhibitors is effective with optimal neuroprotection. Recent clinical data support these mechanisms: PCSK9 inhibitors not only lower LDL-C and Lp(a) but also reduce systemic inflammatory markers (e.g., high-sensitivity C-reactive protein [hs-CRP], interleukin-6). Early adjunctive use of evolocumab in AIS is associated with reduced early neurological deterioration, highlighting that its effects extend beyond lipid lowering to modulating immune pathways in both the central and peripheral systems. As a promising multitarget therapeutic strategy for AIS, PCSK9 inhibitors target the interconnected pathways of lipid metabolism and neuroinflammation. Future studies should address critical challenges such as defining the optimal therapeutic time window, improving BBB penetrability, and refining patient stratification to translate their neuroprotective effects into clinical benefits for stroke patients.