Caspase-2 is involved in IFN-γ primed THP-1 derived macrophages cell death through regulating caspase-8 activation

Pro-inflammatory macrophage cell death is essential for resolving inflammation, yet the subtype-specific mechanisms governing this cell death remained unclear. Herein, THP-1-derived macrophages were polarized into pro-inflammatory (M1) or anti-inflammatory (M2) subtypes and exposed to lipopolysaccharide. M1 cells exhibited higher DNA fragmentation, caspase-3 cleavage, and lactate dehydrogenase release. Pharmacologic inhibition or genetic knockdown of caspase-2 effectively attenuated LPS-triggered M1 macrophage cell death. Mechanistic analyses excluded contributions of the mitochondrial apoptotic pathway, as no Bid cleavage, mitochondrial membrane potential dissipation, or rescue effect of cyclosporin A were detected. IFN-γ pretreatment enhanced caspase-8 cleavage, while caspase-2 deficiency consistently blocked caspase-8 activation under diverse death stimuli: LPS, etoposide, tumor necrosis factor-related apoptosis-inducing ligand, and hydrogen peroxide. IFN-γ priming alone triggered caspase-2 cleavage without inducing cell death, and this pre-activated caspase-2 pool strongly amplified subsequent LPS-mediated caspase-8 activation. Collectively, our work identifies a non-canonical, mitochondria-independent caspase-2/caspase-8 axis that selectively drives LPS-induced cell death in IFN-γ-primed THP-1 macrophages. This pathway acts as a self-regulatory feedback loop to eliminate hyper-inflammatory macrophages and maintain immune homeostasis, providing a novel mechanistic framework for understanding subtype-specific macrophage cell death.