The Role Of Retinol Binding Protein 4 And Related Factors In Mouse Psoriasis Model

Background and Objective:Psoriasis is a common chronic,systemic,inflammatory disease,which has been reported to be associated with metabolic disorders.Psoriasis patients always combined with vitamin A metabolism disorder.Retinol-binding protein-4(RBP4)is the only carrier that mobilize vitamin A and it is relevant to insulin resistance,obesity and type II diabetes mellitus.Many studies have reported that the serum RBP4 levels are different in patients with psoriasis,but the changes seem to be bidirectional.After RBP4 binding with retinol,the complex moves to the target tissue and meet with RBP4 receptor,a transmembrane protein called STRA6.STRA6 will transfer retinol into cells and activating a series of following signal pathways.So,some people may assume that retinol,RBP4 and STRA6 may have a crucial role in the mechanisms of psoriasis.In this study,we intend to create a mice psoriasis model and use it as a tool to study the changes in vitamin A related molecules.Objects:Twenty female Bab/c mice between 8-12 weeks old were shaved on the back and randomized divided into two groups.Group A and Group B:imiquimod(IMQ)treatment fot consecutive 3/6 days.Ten female Bab/c mice were used as control groups.Group C and Group D:each group had 5 mice.Using Vaseline cream as control for 3/6 days.On the day 4 and day 7 extract the serum,skin from the skin lesion and normal areas of the mice.Methods:1.Observe the change of the skin.Using modified PASI to evaluate the severity of psoriasis and detect the width of the skin.2.The levels of serum IL-23?IL-17A?TNF ??RBP4?STRA6 in different groups were detected by enzyme-linked immunosorbent assay(ELISA).3.Skins from the lesioned and non-lesioned areas were dyed with Harris' hematoxylin and eosin for histological analysis.4.Real-time quantitative PCR(RT-PCR)was used to detect the levels of RBP4 and STRA6 mRNA in skins from the lesioned and non-lesioned areas in different groups.5.Immunohistochemistry was used to detect the levels of RBP4 and STRA6 protein in skin tissues of different groups.Results:1.IMQ groups present with erythema,scales and skin thickening.With the time prolonged,the skin changes were more obvious.Modified PASI scores were elevated in day 2 or 3,peaked at day 7.Trasient paresthesia were observed at day 3 or 4 in IMQ mice.2.Histopathology showed the tested skin of group B revealed hyperkeratosis,parakeratosis,severe acanthosis,moderate rete ridge formation,accompanied by focal munro/kogoj abscess,and the granular layer in some areas were moderatly thickening.In the superficial layer of dermis,there were severe lymphocytic infiltration.The histopathology of the normal skin from group B revealed normal epidermis structure but there were some inflammatory cells infiltrate in the dermis,mostly lymphocytes and histocytes.Group D displayed normal dermis as well as epidermis.3.RT-PCR results showed that the levels of IL-17A?TNF-??IL-23?RBP4 mRNA were higher in lesioned skin in group B than the control and group A,while the STRA6 mRNA level was lower.But no statistical significances between these differences.Between the lesioned and non-lesioned skins in group B,the levels of IL-17A?TNF-??IL-23?RBP4?STRA6 mRNA were higher in lesioned skins.IL-17A?IL-23 presented with statistical significance(P=0.030,P=0.028).4.The levels of RBP4 protein in Group A and B non-lesioned skins were negative.In Group A lesioned skin area the expression level was-~+.Group B lesioned skin's expression was +~++.There were a large area of positive cells in epidermis.Mainly locate in stratum corneum,keratinocytes' cytoplasm.Monocytes were dyed positively in the cytoplasm,dermis.STRA6's expressions were negative in control groups and group A and B's non-lesioned skin areas.Group A lesioned skin's STRA6 expression level was-~+.Group B lesioned skin's STRA6 expression level was ++~+++.Large scales of positive cells in the epidermis,mainly located in the superficial layer of stratum corneum,keratinocytes' cytoplasm.Some sections were also dyed positively in the stratum granulosum and basal layer.In the dermis,there were also lots of positive cells in the cytoplasms of monocytes.5.The levels of serum IL-23(P<0.0001).IL-17A(P=0.048).TNF a(P=0.003).RBP4(P=0.0445)were significantly higher in IMQ groups compared with the control groups.Although STRA6 level was higher in IMQ groups but there was no statistical significance(P=0.251).Retinol levels were around the same in all groups(P=0.770).Group A and B had no statistical significance.Conclusion:1.Application of IMQfor consecutive 6 days will induce psoriasis both in vivo and in vitro in the bab/c mice' skin.And the phenotype is time-dependent.2.IMQ can induce transient paresthesia in the lesioned area in bab/c mice,which will help the reaserch against psoriasis pruritus.3.First found in psoriasis mice that expression level of RBP4 and STRA6 was elevated in the lesioned skin.More RBP4 together with more retinol will form a comlex,by combining with the upregulated STRA6,more retinol was moved into the target cells.This might be a potential mechanism of the formation of psoriasis lesion.4.Fisrt found in psoriasis mice' serum that the RBP4 level is higher than the controls,with statistical significance.The upregulated RBP4 will help transport more retinol to the target tissue.5.There might be a redistribution in retinol in psoriasis mice.Because the skin's demand of retinol is increased,the serum level of retinol should be upregulated.But STRA6 facilitates lots of retinol move into the cells,the serum level of retinol is then around the same level with the controls.