Caspase-8-and Gasdermin D (GSDMD)-Dependent PANoptosis Participate in the Seasonal Atrophy of Scented Glands in Male Muskrats

The muskrat (<i>Ondatra zibethicus</i>) is an animal with special economic significance whose scented glands rapidly atrophy during the non-breeding season, but the mechanism of atrophy is not clear, with significant differences in apoptotic and pyroptotic signaling pathway expression according to transcriptome sequencing. During the non-breeding season, key apoptosis-related genes such as <i>Tnfr1</i> (TNF Receptor Superfamily Member 1A), <i>TRADD</i> (TNFRSF1A Associated via Death Domain), <i>FADD</i> (Fas Associated via Death Domain), <i>Casp-8</i> (Cysteine-aspartic proteases-8), and <i>Bax</i> (Bcl-associated X protein) were upregulated in the scented glands, while <i>Bcl2</i> (B-cell lymphoma-2) expression was downregulated. In the classical pyroptosis pathway, the mRNA expression levels of key genes including <i>Nlrp3</i> (the Nod-like receptor family pyrin domain-containing 3), <i>ASC</i> (the apoptosis-associated speck-like protein), <i>Casp-1</i> (Cysteine-aspartic proteases-1), <i>Gsdmd</i> (Gasdermin D), and <i>IL-1β</i> (Interleukin 1 Beta) were higher during the non-breeding season, similar to the transcription level of <i>Ripk1</i> (Receptor Interacting Serine/Threonine Kinase 1) in the non-canonical pyroptosis pathway, while <i>TAK1</i> (transforming growth factor kinase) expression was downregulated in this latter pathway. TUNEL assays and immunofluorescence analysis indicated increased apoptosis and GSDMD and Caspase-8 protein levels during the non-breeding season. Indeed, the protein levels of GSDMD-N, Caspase-8 p43, and Caspase-8 p18 were significantly higher during the non-breeding season, while the GSDMD levels were significantly lower compared to the secretion season. These results suggest that apoptosis and pyroptosis play regulatory roles in scented gland atrophy and that there is an interplay between them during this process.