Psoriasis is a systemic inflammatory disease, associated with metabolic disorders, including high level of lowdensity lipoprotein. PCSK9, which promotes the degradation of low-density lipoprotein receptors and, therefore, the increased concentration of circulating low-density lipoprotein, is also involved in inflammation. This study aims to examine the role of PCSK9 in psoriasis and to investigate the potential of topically applying small interfering RNA targeting Pcsk9 as a psoriasis treatment. We investigated the expression of PCSK9 in lesions of psoriasis patients and imiquimod-induced psoriatic reactions in Pcsk9-knockout and Pcsk9 small interfering RNA-treated mice, and we also used cultured human keratinocytes to investigate the role of PCSK9 in regulating cell proliferation and apoptosis. We found that PCSK9 is overexpressed in psoriatic lesions and that suppressing Pcsk9 can decrease the inflammatory reaction induced by imiquimod treatment and inhibit hyperproliferation of keratinocytes. We also found that suppressing PCSK9 can significantly alter the cell cycle and induce apoptosis of human keratinocytes. Taken together, our findings indicate that PCSK9 plays an important role in psoriasis and may be a therapeutic target.
Nuclear receptor interacting protein 1 (NRIP1, also known as RIP140) is a co-regulator for various transcriptional factors and nuclear receptors, and has been shown to take part in many biological and pathological processes, such as regulating mammary gland development and inflammatory response.The aim of this study is to investigate the expression of NRIP1 and to explore its roles in the pathogenesis of psoriasis. Thirty active psoriasis patients and 16 healthy volunteers were enrolled for this study. qRT-PCR analyses found that both NRIP1 and RelA/p65 were elevated in psoriatic lesions compared to psoriatic non-lesions and normal controls, and also overexpressed in peripheral blood mononuclear cell (PBMCs) of psoriasis patients. Suppression of NRIP1 in HaCaT cells could significantly inhibit cell growth and induce apoptosis, and the suppression of NRIP1 in CD4+ T cells isolated from psoriasis patients could downregulate the expression of RelA/p65 and decrease the secretion of IL-17. Furthermore, in Nrip1 knockout mice, IMQ-induced inflammation of skin was delayed and the RelA/p65 expression in lesions was reduced. In conclusion, our data suggests that NRIP1 is overexpressed both in skin and PBMCs of psoriasis patients and may be involved in the abnormal proliferation and apoptosis of keratinocytes, as well as the immune reaction through the regulation of RelA/p65. Therefore, NRIP1 may be a potential therapeutic target for psoriasis.
Our previous studies found that deletion of nuclear receptor interacting protein 1 (Nrip1) extended longevity in female mice and delayed cell senescence. The current study investigates the role of NRIP1 in regulating functions of adipose-derived mesenchymal stem cells (ADMSCs) and explores the mechanisms of NRIP1 in skin aging. We first verified the skin aging phenotypes in young (6 months) and old (20 months) C57BL/6J (B6) mice and found deletion of Nrip1 can delay skin aging phenotypes, including reduced thickness of dermis and subcutaneous white adipose tissue (sWAT), as well as the accumulation of senescent cells in sWAT. In ADMSCs isolated from sWAT, we found that deletion of Nrip1 could decrease cell proliferation, prevent cell apoptosis, and suppress adipogenesis. Interestingly, deletion of Nrip1 also reduced cell senescence and maintain cell quiescence of ADMSCs. Moreover, the expressions of genes associated with senescence (p21, and p53), inflammation (p65, IL6, and IL1a), and growth factor (mTOR, Igf1) were reduced in Nrip1 knockout ADMSCs, as well as in siNrip1-treated ADMSCs. Suppression of Nrip1 by siNrip1 also decreased the expressions of mTOR, p-mTOR, p65, and p-p65 in ADMSCs. Reduced expressions of p65 and p-p65 were also confirmed in the skin of Nrip1 knockout mice. These findings suggest that NRIP1 plays an important role in delaying skin aging by reducing ADMSCs senescence and maintaining ADMSCs quiescence.
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