CALB2 Overexpression Attenuates Neuropathic Pain by Inhibiting Oxidative Stress and Modulating Microglia M1/M2 Polarization Through Activation of the cAMP/CREB Pathway

Abstract

Neuropathic pain (NP) is a chronic condition with high morbidity. Current treatments to manage this pain are largely ineffective due to a limited understanding of the underlying mechanisms. Based on the GSE2636 and GSE24982 datasets, NP-associated differentially expressed genes (DEGs) were screened by the bioinformatics approach. A rat L5 spinal nerve ligation (SNL) model and lipopolysaccharide (LPS)-induced BV2 cell model were adopted. Two key genes were identified, including calbindin-2 (CALB2) and sodium voltage-gated channel alpha subunit 1 (SCN1A), both of which were downregulated in the SNL rat model. Immunofluorescence staining demonstrated partial colocalization of CALB2 with Iba1-positive microglia. CALB2 overexpression promoted viability and inhibited apoptosis of LPS-induced BV2 cells. CALB2 overexpression also facilitated the shift of microglia from M1 to M2 phenotype, as evidenced by decreased levels of tumor necrosis factor-alpha (TNF-α) and interleukin-1beta (IL-1β) and elevated levels of IL-10 and arginase 1 (ARG1). Additionally, after CALB2 overexpression, the levels of reactive oxygen species (ROS) and malondialdehyde (MDA) were lowered, while the levels of glutathione (GSH) and superoxide dismutase (SOD) were increased. In SNL rats, CALB2 overexpression enhanced the paw withdrawal threshold and paw withdrawal latency. Mechanistically, CALB2 overexpression inhibited NP development by activating the cyclic adenosine monophosphate/cAMP response element-binding protein (cAMP/CREB) signaling pathway. CALB2 overexpression inhibits oxidative stress and promotes microglia transition from M1 to M2 phenotype by activating the cAMP/CREB pathway, which in turn attenuates NP.