Current Insights into the Molecular Mechanisms of Intracranial Atherosclerosis and Their Therapeutic Implications

Intracranial atherosclerosis (ICAS) is a distinct, inflammation-dominant vasculopathy and a leading cause of global stroke morbidity. Unlike extracranial atherosclerosis (ECAS), which often utilizes compensatory positive remodeling to maintain patency, ICAS is characterized by a unique architecture and a localized antioxidant gap that favor maladaptive negative remodeling. We critically analyze the molecular cascade initiated by the breakdown of the Piezo-type mechanosensitive ion channel component 1 (PIEZO1) and the Krüppel-like factor 2/4 (KLF2/4) mechanotransduction axis, which triggers endothelial nitric oxide synthase (eNOS) uncoupling and establishes a state of chronic inflammation. This environment facilitates the subendothelial lipid retention of oxidized low-density lipoprotein (oxLDL), a process exacerbated by the intracranial deficiency of Apolipoprotein A-I (ApoA-I) and impaired glymphatic clearance. Crucially, we evaluate how these metabolic and mechanical insults drive vascular smooth muscle cell (VSMC) phenotypic switching; the transdifferentiation of contractile VSMCs into macrophage-like foam cells accounts for up to 60% of the plaque’s lipid-laden pool and destabilizes the fibrous cap. This vascular failure directly compromises the neurovascular unit (NVU), leading to pericyte dropout and blood–brain barrier breakdown. Beyond environmental stressors, we highlight the ring finger protein 213 (RNF213) variant as a critical genetic determinant of this susceptibility. Shifting the clinical paradigm from simple luminal narrowing toward the identification of the vulnerable plaque, we discuss how High-Resolution Vessel Wall Imaging (HR-VWI) and microRNA biomarkers can identify unstable lesions. By integrating these molecular and imaging signatures, we propose a precision medicine framework centered on the NLR family pyrin domain containing 3 (NLRP3) inflammasome and the NVU to effectively mitigate the high residual recurrence risk that persists under conventional therapy.