Evaluation of Topical Apremilast Nanoparticles in the Treatment of Plaque Psoriasis: Clinical, Histopathological and Immunohistochemical Study

Psoriasis is a chronic immune-mediated inflammatory skin condition with a strong genetic predisposition and an autoimmune pathogenic characteristic . Its worldwide prevalence is up to 2% but this varies between different geographic regions . In Egypt, the prevalence of psoriasis ranges between 0.19% and 3% .

Individuals with psoriasis frequently endure marked psychological distress. This includes social embarrassment, reduced self esteem, anxiety, depression, and an increased tendency toward suicidal ideation and behavior .

Psoriasis Skin lesions are usually symmetrical, sharply demarcated, with red or pink raised plaques, and covered with silvery scales. These plaques reflect key pathological processes, including inflammation, keratinocyte hyperproliferation, and angiogenesis .

Cellular responses to environmental stimuli and intracellular signaling in various cell types-including myeloid, lymphoid, and other inflammatory cells-are mediated by intracellular "second messengers," particularly cyclic adenosine monophosphate (cAMP) .

Phosphodiesterase4 (PDE4) is one of the major cAMP-selective PDEs expressed in epithelial cells . It is also present in several mesenchymal cell types, including dermal keratinocytes, smooth muscle cells, vascular endothelial cells, and chondrocytes, By decreasing intracellular cAMP, PDE4 promotes production of pro-inflammatory mediators and decreases production of anti-inflammatory mediators. Conversely, inhibition of PDE4 increases the intracellular concentration of cAMP and selectively blocks pro-inflammatory cytokines, such as TNF-α, IFN-γ, and IL-2 production from peripheral blood monocytes and T cells.