IRAK-M attenuates pain hypersensitivity and anxiety-like behaviors in a nitroglycerin-induced chronic migraine mouse model with concomitant reductions in microglial activation and neuroinflammation.

BACKGROUND: Chronic migraine (CM) is a disabling neurological disorder in which neuroinflammatory mechanisms and central sensitization are thought to contribute to disease pathophysiology. Interleukin-1 receptor-associated kinase M (IRAK-M), which is predominantly expressed in microglia in the central nervous system (CNS), is an endogenous negative regulator of innate immune signaling. Previous studies have linked IRAK-M to the restraint of Toll-like receptor 4 (TLR4) signaling and NLR family pyrin domain-containing 3 (NLRP3) inflammasome-related responses. However, the role of IRAK-M in CM-related pathophysiology and associated neuropsychiatric comorbidities remains unclear. This study aimed to investigate the function of IRAK-M and its underlying molecular mechanisms in a mouse model of chronic migraine.

METHODS: Mice were repeatedly given intraperitoneal injections of nitroglycerin (NTG; 10 mg/kg) to create a chronic migraine model. Mechanical and thermal sensitivity were assessed using von Frey filaments and the hot-plate test, respectively; light aversion and anxiety-like behaviors were evaluated using the light-aversion test, open-field test, and elevated plus-maze test. To further clarify the role of IRAK-M, both transgenic genetic engineering approaches and adeno-associated virus (AAV)-mediated expression strategies were employed. The underlying molecular mechanisms were further investigated using quantitative PCR, immunoblotting, immunofluorescence, and three-dimensional reconstruction.

RESULTS: Repeated administration of NTG increased IRAK-M protein in the trigeminal nucleus caudalis (TNC). IRAK-M deficiency exacerbated mechanical and thermal hyperalgesia, increased c-Fos and CGRP expression, and enhanced microglial activation; these changes were accompanied by increased TLR4/NF-κB-related signaling, NLRP3 inflammasome activation, and GSDMD cleavage. Conversely, TNC-targeted IRAK-M overexpression attenuated pain hypersensitivity and anxiety-like behavioral alterations and was accompanied by corresponding reductions in neuroinflammatory molecular and cellular readouts. These findings support IRAK-M as an important regulator of central sensitization and neuroinflammatory responses in a chronic migraine model.

CONCLUSIONS: Our findings identify IRAK-M as an important preclinical regulator of microglial reactivity and neuroinflammatory responses in the NTG-induced chronic migraine model. IRAK-M manipulation was accompanied by bidirectional changes in TLR4/NF-κB- and NLRP3/GSDMD-related signaling, pain hypersensitivity, and anxiety-like behavioral alterations. These findings provide a preclinical rationale for further investigation of IRAK-M-related neuroimmune signaling in migraine.

CLINICAL TRIAL NUMBER: Not applicable.