Immunohistochemical insights into oxidative stress and programmed cell death in primary and COVID-associated rhino-orbital-cerebral mucormycosis patient tissues.

Mucormycosis is an invasive fungal infection with very high mortality in patients with diabetic ketoacidosis, iron overload, or immune suppression. Rhizopus and Mucor are the most common etiological agents, with rhino-orbital-cerebral mucormycosis being the most frequent form of the disease. In this study, we sought to determine the activation of apoptosis, necroptosis, ferroptosis, and pyroptosis along with oxidative stress markers, in formalin-fixed paraffin embedded rhino-orbital tissues from patients with mucormycosis and COVID-19-Associated-Mucormycosis (CAM). We observed increased expression of 3-nitrotyrosine and phosphorylated Nuclear factor Erythroid 2-related factor 2, suggesting the presence of oxidative stress in these tissues. Elevated levels of CD71, phosphorylated MLKL (Mixed lineage kinase domain-like protein), and cleaved caspase 3 were detected in both mucormycosis and CAM tissues, indicating differential activation of ferroptosis, necroptosis and apoptosis during fungal infection. Notably, cleaved gasdermin D was not detected, indicating that pyroptosis does not play a significant role in mediating host lytic cell death during invasive mucormycosis. Our findings, which identify differential activation of programmed cell death pathways directly in human tissues, meet an important critical gap in the mucormycosis literature and highlight viable targets for future therapeutic interventions.