T cells in resolved allergic contact dermatitis steer tissue inflammation and MMP-12-driven tissue modulation

An overview of matrix metalloproteinase-12 in multiple disease conditions, potential selective inhibitors, and drug designing strategies

Matrix metalloproteases (MMPs) are the proteolytic enzymes accountable for extracellular matrix (ECM) modification through their Zn2+-dependent catalytic activity. Among these, MMP-12 is one of the crucial MMPs that contributes to various disease states including different types of cancers and other major pathophysiological conditions including COPD, asthma, emphysema, skin diseases, arthritis, vascular diseases, and neurological disorders. The majority of the MMP-12 inhibitors should have three constitutional pharmacophoric features (i.e., a hydrophobic group to occupy the S1' pocket, a zinc-binding motif for chelating to the catalytic Zn2+ ion present at the catalytic site, and a flexible and hydrogen bond forming linker region between the S1' pocket substituent and the zinc chelating group for interacting with the catalytic and Ω-loop amino acid residues). This review mainly focuses on the various roles of MMP-12 in different diseases along with the structural comparison with other MMPs as well as promising and MMP-12-selective inhibitors and molecular modeling studies performed on MMP-12 inhibitors. Therefore, this review will provide comprehensive information to the researchers for designing effective and MMP-12-selective inhibitors for therapeutic advancement in the future.

Skin-resident T Cells Contribute to the Dynamic Disease Manifestations of Psoriasis

The human skin forms a dynamic barrier to physical injuries and microbial invasion. Constant interactions between stroma and tissue-confined immune cells maintain skin homeostasis. However, the cellular interactions that maintain skin health also contribute to focal immunopathology. Psoriasis is a common disease that manifests with focal pathology induced by environmental triggers in genetically susceptible individuals. Within psoriasis plaques, cross-talk between skin-resident T cells and stroma cells leads to chronic inflammation. Inflammatory cytokines such as TNF-α, IL-17, IL-22, and IL-23 amplify the local chronic inflammation and sustain the well-demarcated thick and scaly plaques that characterize the disease. In resolved lesions, T cells remain poised for IL-17 and IL-22 production, and postinflammatory epigenetic modifications lower the threshold for initiation of local relapse. This review focuses on how tissue-resident memory T cells contribute to the onset, maintenance, resolution, and relapse of psoriasis.

The Involvement of Cysteine-X-Cysteine Motif Chemokine Receptors in Skin Homeostasis and the Pathogenesis of Allergic Contact Dermatitis and Psoriasis

Members of the C-X-C motif chemokine receptor (CXCR) superfamily play central roles in initiating the innate immune response in mammalian cells by orchestrating selective cell migration and immune cell activation. With its multilayered structure, the skin, which is the largest organ in the body, performs a crucial defense function, protecting the human body from harmful environmental threats and pathogens. CXCRs contribute to primary immunological defense; these receptors are differentially expressed by different types of skin cells and act as key players in initiating downstream innate immune responses. While the initiation of inflammatory responses by CXCRs is essential for pathogen elimination and tissue healing, overactivation of these receptors can enhance T-cell-mediated autoimmune responses, resulting in excessive inflammation and the development of several skin disorders, including psoriasis, atopic dermatitis, allergic contact dermatitis, vitiligo, autoimmune diseases, and skin cancers. In summary, CXCRs serve as critical links that connect innate immunity and adaptive immunity. In this article, we present the current knowledge about the functions of CXCRs in the homeostasis function of the skin and their contributions to the pathogenesis of allergic contact dermatitis and psoriasis. Furthermore, we will examine the research progress and efficacy of therapeutic approaches that target CXCRs.