Calpeptin and protein kinase C inhibition suppress exosome-associated inflammatory signaling and epidermal dysregulation in a 3-dimensional psoriatic skin model.

Psoriasis is a chronic inflammatory skin disorder characterized by dysregulated cytokine signaling and keratinocyte hyperproliferation, in which extracellular vesicles, particularly exosomes, play key roles in mediating intercellular inflammatory communication. In this study, we evaluated the pharmacological effects of calpeptin and bisindolylmaleimide I (BIM-I), inhibitors of calpain and protein kinase C previously reported to modulate extracellular vesicle-associated pathways, in a 3-dimensional human psoriatic skin model. Both inhibitors significantly reduced the expression of proinflammatory cytokines, keratinocyte activation marker, and exosome-related marker, including interleukin (IL)-1β, tumor necrosis factor-α, IL-8, interferon gamma, IL-21, IL-20, CC chemokine ligand-20, keratin 6A, CD9, and CD63, consistent with attenuation of psoriasis-associated inflammatory signaling. BIM-I additionally suppressed IL-22 and IL-6 expression and restored epidermal ultrastructural features, including desmosome density, to levels comparable with normal skin. Integrated proteomic and immunohistochemical analyses revealed distinct downstream biological responses associated with modulation of exosome-associated markers and pathways. Calpeptin treatment was associated with enrichment of endoplasmic reticulum stress-related pathways, as indicated by increased growth arrest and DNA damage-inducible protein 153 and glucose-regulated protein 78 expression, whereas BIM-I preferentially regulated cytoskeletal organization and keratinocyte differentiation, accompanied by reduced expression of growth arrest and DNA damage-inducible protein 153, glucose-regulated protein 78, and keratin 16. Collectively, these findings demonstrate that pharmacological inhibition of calpain and protein kinase C attenuates psoriatic inflammation and epidermal dysregulation and is associated with modulation of exosome-associated markers and pathways, together with differential regulation of endoplasmic reticulum stress and cytoskeletal networks. SIGNIFICANCE STATEMENT: This study demonstrates that pharmacological inhibition of calpain and protein kinase C attenuates inflammatory signaling and keratinocyte activation in a 3-dimensional psoriatic skin model, highlighting exosome-associated pathways as key regulators of disease pathology. Distinct mechanisms involving endoplasmic reticulum stress modulation and cytoskeletal regulation provide insight into how targeting vesicle-mediated intercellular communication may offer therapeutic potential in psoriasis.