Nitrogen Mustard Disrupts Bioenergetics and Activates Oxidative Stress-Induced Cell Death Pathways in Human Keratinocytes

Abstract

Nitrogen mustard (HN2) is a highly reactive bifunctional alkylating agent that causes severe skin injury. To define its impact on keratinocyte bioenergetics and stress responses, we examined mitochondrial function, metabolism, and cell death signaling in human HaCaT cells. Seahorse analysis showed that HN2 caused time- and concentration-dependent suppression of oxidative phosphorylation, including reductions in basal, adenosine 5′-triphosphate-linked, and maximal oxygen consumption. Glycolytic activity was similarly impaired, with decreased extracellular acidification, reduced glucose-stimulated glycolysis, and loss of glycolytic capacity and reserve, indicating broad metabolic dysfunction. HN2-induced bioenergetic impairment triggered rapid nuclear accumulation of nuclear factor erythroid 2-related factor 2 (Nrf2) and upregulation of antioxidant and mitochondrial regulatory genes (HO-1, NQO1, GSTA4, and PGC1α). In parallel, HN2 activated multiple programmed cell death pathways, including apoptosis, autophagy, and ferroptosis, as evidenced by corresponding alterations in Bax, Bcl-xL, LC3-II, SQSTM1/p62, caspase-2, caspase-9, GPx4, TFRC, and ACSL4. Cell cycle analysis identified cells in G2/M as particularly susceptible to HN2, which exhibited enhanced apoptotic signaling. N-acetylcysteine attenuated Nrf2 activation, preserved mitochondrial and glycolytic function, and reduced activation of cell death pathways, demonstrating a central role for oxidative and electrophilic stress in HN2 toxicity. These findings reveal a novel mechanism by which HN2 disrupts keratinocyte bioenergetics to drive stress-dependent cell death and highlight antioxidant intervention as a potential strategy to mitigate HN2-induced skin injury.