Investigation Of Serum 5-hydroxytryptamine Level And The Expression Of Its Receptors On T Cells In Systemic Lupus Erythematosus

Objective 5-hydroxytryptamine(5-HT),also known as serotonin,has multiple physiological functions including serving as a neurotransmitter and an immunomodulatory factor.The objective of the current study is to investigate the5-HT level in the serum and its receptors 5-HT2AR and 5-HT7R in the T cells of patients with systemic lupus erythematosus(SLE).We sought to understand their potential applications in monitoring disease activity and contributions to the SLE pathogenesis.Method A cohort of 35 SLE patients and 30 healthy controls were included in the study.The serum level of 5-HT was determined using enzyme linked immunosorbent assay(ELISA).The mRNA expression level of 5-HT2AR and 5-HT7R was determined by quantitative real-time polymerase chain reaction(RT-q PCR)and normalized to the GAPDH mRNA level.In addition,blood count,laboratory findings(erythrocyte sedimentation rate(ESR),c-reactive proteins,complements)and SLEDAI score were collected.Results Compared with healthy controls,the serum 5-HT level in SLE patients was significantly reduced(38.02±20.55 vs.179.03±46.48,P<0.001),and positively correlated with platelet count and serum C3 and C4 levels(P<0.01),whereas it negatively correlated with ESR and SLEDAI(P<0.01).The 5-HT2AR mRNA level was elevated in the CD4+T cells of SLE patients compared to healthy controls(1.67±0.58 vs.0.97±0.2,P<0.001),while the decreased 5-HT7R mRNA level was observed in these patients(0.36±0.19 vs.1.03±0.18,P<0.001),and both of them were significantly correlated with serum 5-HT level(P<0.05).In CD4+T cells,the5-HT2AR level negatively correlated with the C3 and C4 levels(P<0.01),whereas it positively correlated with SLEDAI(P=0.004).In contrast,the 5-HT7R level positively correlated with C3/C4 levels and negatively correlated with ESR and SLEDAI(P<0.01).In CD8+T cells,both 5-HT2AR and 5-HT7R levels were lower in the SLE patients than in the healthy controls and both positively correlated with serum 5-HT and C3/C4 levels(P<0.05),in addition,5-HT7R expression was negatively correlated with SLEDAI score(P=0.016).Conclusions:Our results showed significantly altered levels of serum 5-HT and its receptors 5-HT2AR and 5-HT7R mRNA in CD4+ and CD8+ T cells in the SLE patients.They may serve as useful markers of SLE disease activity in the clinic.Further investigation of the role of 5-HT and its receptors in regulating T cell functions as well as SLE pathogenesis is warranted.