Psoriasis, an immune-mediated chronic inflammatory skin disease, is featured with epidermal hyperplasia, angiogenesis, and inflammatory cell infiltration [15, 16]. It is a key psoriasis treatment to inhibit these cellars events. Evidences indicated that numerous internal and external factors might participate in psoriasis pathogenesis, including the immune system, environmental factors, keratinocytes and susceptibility genes [17]. Owing to the complexity of the cause of psoriasis, its pathogenesis has not yet been fully understood.
Increasing evidence has shown that abnormally expressed microRNA (miRNA) takes effects on psoriasis progression, such as miR-146a [18], miR-125b [19] and miR-135b [20]. These dysregulated miRNAs play an important role in diagnosis and treatment and have attracted increasing attention for their therapeutic potential in diseases. For instance, in psoriasis patients, the level of miR-205-5p was downregulated, and played its roles by targeting Ang-2, VEGFA and BAMBI, and deactivating the Wnt/β-catenin and MAPK signaling pathways, which provided a potential therapeutic target for clinical treatment of psoriasis [21]. Work by Wang et al. established that miR-223 was overexpressed in psoriatic lesions and in IL-22-stimulated HaCaT cells, and increased proliferation and inhibited apoptosis of IL-22-stimulated keratinocytes via the PTEN/Akt pathway [8]. Another study demonstrated that miR-876-5p was down-regulated in psoriasic tissue and blood of patients and would be expected to be biomarker and potential therapeutic targets for the treatment of psoriasis [22]. In this study, the serum expression level of miR-106a-5p in psoriasis patients was higher than that in healthy control, which was consistent with two previous studies [5, 11]. We further studied the correlation between miR-106a-5p and PASI score. Experimental results demonstrated the correlation between the expression levels of miR-485-5p and PASI score were positive significantly, which indicated a probable connection between psoriasis progression and miR-106a-5p. These results motivated us to study the role of miR-106a-5p in psoriasis further.
MiR-106a-5p was reported to be dysregulated in various of diseases, such as prostate cancer[23], atherosclerosis [24] and cervical cancer [25]. The clinical value of miR-106a-5p in diseases attracted researcher attention. As reported by Zhang et al., miR-106a-5p level was downregulated in osteoarthritis (OA) samples and IL-1b-treated chondrocytes, miR-106a-5p overexpression led to proliferation promotion and apoptosis inhibition in chondrocytes treated by IL-1β[26]. Another study in HPV-16-associated cervical cancer reported that miR-106a-5p played an important role in regulatory mechanism of cervical squamous cell carcinoma (CSCC) and could be a potential therapeutic target in HPV-associated cervical cancer [25]. Considering the dysregulation of miR-106a-5p in the serum of psoriasis patients, we further explored whether serum miR-106a-5p could differentiate between the psoriasis patients and the healthy. The area under the ROC curve (AUC) of miR-106a-5p on diagnosis of psoriasis was 0.901 with a sensitivity of 74.60% and specificity of 91.7% at the cutoff value of 1.195, indicating miR-106a-5p has ability to distinguish the psoriasis patients from healthy control.
In this study, it was found that the protein levels of IL-17A, IL-22 and TNF- alpha were significantly increased in serum. The result demonstrated that inflammation play an important role in psoriasis. We further explored the correlations between the serum expression level of miR-106a-5p and inflammation cytokines. Results indicated that serum levels of miR-106a-5p were positively correlated with the protein levels of IL-22, IL-17A and TNF-alpha. Therefore, it came to this conclusion that upregulated miR-106a-5p might promote the occurrence and development of psoriasis through promoting inflammatory response.
HaCaT cells are immortalized cells, which are commonly used in the studies relevant to psoriasis [13]. To mimic conditions of psoriatic keratinocytes, HaCaT cells were induced with M5 (consisting of IL-17A, IL-22, IL-1alpha, TNF-alpha and Oncostatin M) as previous reported [27]. Therefore, we established a cell model of highly proliferative psoriatic keratinocytes via treating HaCaT cells by M5. It is found that the expression level of miR-106a-5p was apparently increased in M5-treated HaCaT cells, which was consistent with the results observed in the serum of psoriasis patients. Meanwhile, the upregulation of miR-106a-5p in M5-treated HaCaT cells significantly promoted its proliferation. Additionally, the protein levels of inflammation cytokines (IL-17A, IL-22 and TNF- alpha) were all increased significantly in M5-treated HaCaT cells. These results suggested that miR-106a-5p might be a potential treatment target in psoriasis.
In conclusion, our work demonstrates that miR-106a-5p had a high expression in psoriasis patients and can distinguish psoriasis patients from healthy controls. MiR-106a-5p might be involved in the disease progression through regulating inflammatory response. Our results provide new insight of miR-106a-5p and may contribute to the development of target for psoriasis treatment.