The Relevance And Role Of Perfluoroalkyl Substances In Chronic Spontaneous Urticaria

Urticaria is a common immune-related skin disease mediated by allergy and its clinical manifestations are wheals(with or without angioedema)and pruritus.Urticaria is related to a variety of factors such as heredity,environment,and immunity,and its specific mechanism is still unclear.Previous studies suggested immunotoxicity of perfluoroalkyl substances(PFASs),but contradictory findings were reported for the associations of PFASs with allergies.At present,the relationship between chronic spontaneous urticaria(CSU)and PFASs has not been reported.Through four studies,this paper expounds on the prevalence of CSU in Chinese public officials,and the risk factors for patients with CSU.The relationship between occurrence and development and prognosis of CSU and PFASs,and its possible mechanism.The summaries of each part are as follows:Study 1: Prevalence and risk factors of chronic spontaneous urticaria in public officialsObjectives: To explore the prevalence of chronic spontaneous urticaria(CSU)and the risk factors of CSU in a cohort of public officials.Methods: This study was based on a baseline survey of the Hunan Provincial Government Employees Chronic Disease Cohort Study conducted in five cities in Hunan Province,China,from 2018 to 2019.In the five cities of Changsha,Zhuzhou,Huaihua,Changde,and Xiangtan,all employees in the public sector and state-owned enterprises were invited to take part in our study.Participating employees undergo medical examinations and investigations at the hospital.The survey process included questionnaires,general measurements,dermatological examinations,and the collection of biological specimens.Dermatologists diagnosed participants with urticarial disease and type of urticaria.Anxiety symptoms,depressive symptoms and sleep quality were assessed by Generalized Anxiety Disorder-2(GAD-2),Patient health questionaire-2(PHQ-2),and Pittsburgh Sleep Quality Index(PSQI).Analysis of t-test,chi-square analysis,and Wilcoxon rank-sum test were selected for hypothetical tests according to data distribution.Logistic regression was used to estimate the effect size,and odds ratio(OR)and 95% confidence interval(CI)were presented.Results: A total of 9136 public officials were recruited and included in the analysis.The number of patients with CSU was 195,and the prevalence was 2.1%.Female CSU patients were higher than male CSU patients,and the result was statistically significant(P=0.039).There were no significant differences in living habits such as smoking,drinking,and dietary intake frequency between CSU patients and normal controls.Depressive symptoms and sleep disturbances in CSU patients were 1.85 times and 1.46 times higher than those in healthy controls,respectively.Mediation analysis showed that sleep disturbance was a partial mediator(39.5%)in the relationship between depressive symptoms and CSU.Conclusions: The prevalence of CSU in public officials was 2.1%(195/9136),with significant gender differences.CSU patients are more prone to depressive symptoms and sleep disturbances.The relationship between CSU and depression is mediated by sleep disturbance.Study 2: Perfluoroalkyl substances are linked to incident chronic spontaneous urticaria: A nested case-control studyObjectives: Previous studies suggested immunotoxicity of perfluoroalkyl substances(PFASs),but contradictory findings were reported for the associations of PFASs with allergies.The current study aimed to investigate the association of serum PFASs with incident chronic spontaneous urticaria(CSU)in adults.Methods: A nested case-control study within a longitudinal cohort of7051 government employees in China was conducted.Participants with urticaria at the baseline were excluded.During the first follow-up,70 incident CSU cases were included,And 70 age-and gender-matched healthy controls were randomly selected.In serum samples collected at the baseline,eight PFASs were determined using the UHPLC-MS/MS approach.Results: The median serum concentrations of perfluorobutanoic acid(PFBA)and perfluoroheptanoic acid(PFHp A)were significantly higher in participants with incident CSU.The area under the receiver operating characteristic curve was 0.714(95% CI: 0.60–0.83)based on the joint prediction by PFBA and PFHp A.The Bayesian kernel machine regression showed a nonlinear positive overall effect of the mixture of PFASs,and identified significant single effects of PFBA and PFHp A.Serum interleukin-4 was significantly higher in the case group at baseline,and was positively associated with PFHp A(r=0.24).Causal mediation analysis indicated interleukin-4 as a partial mediator(14.8%)in the association of PFHp A with CSU.Conclusions: In conclusion,serum PFASs are associated with an increased risk of incident CSU,and PFBA and PFHp A might be the effective compounds.Study 3: Association of perfluoroalkyl substances and severity and treatment of chronic spontaneous urticaria.: A Case-Control StudyObjective: To explore the relationship between perfluoroalkyl substances(PFASs)and severity and treatment of chronic spontaneous urticaria(CSU),and to explore the relationship between food intake frequency and PFASs concentration.Methods: 60 CSU patients in dermatology outpatient clinics were continuously collected,and the demographic data,Urticaria activity scores7(UAS7)score and Dermatology Life Quality Index(DLQI)score of the participants were collected.The food intake frequency of the participants was collected through the Food Frequency Questionnaire(FFQ).Participants were followed-up one month later,and the therapeutic effects were compared according to the UAS7 score at the follow-up.The mild CSU group and the moderate-to-severe CSU group were patients with UAS7 scores of 0-15 and 16-42,respectively.After follow-up,the UAS7 score decreased by ≥50% as the CSU treatment effective group,and the UAS7 score decreased by less than 50% as the CSU treatment ineffective group.In serum samples collected at the baseline,the levels of eight PFASs were determined using the UHPLC-MS/MS method.Results: Participants were divided into a mild CSU group and a moderate-to-severe CSU group according to the UAS7 score,and there was no statistical difference in the levels of PFASs between the two groups.According to the UAS7 score at baseline and follow-up,the participants were divided into the CSU treatment ineffective group and the CSU treatment effective group.The median concentrations of perfluorooctane sulfonate(PFOS)in the CSU ineffective group and CSU effective group were 5.89 nmol/L and 8.93 nmol/L,respectively,and there was a statistical difference between the two groups(P=0.034).The intake of beef and mutton,freshwater fish,crab,shellfish,vegetables,and nuts were positively correlated with PFASs,and potato,soy products,sugarsweetened beverages,hamburger,fried chicken,barbecue,popcorn,and pizza were negatively correlated with PFASs.Conclusions: Serum PFOS is associated with the therapeutic efficacy of CSU,and higher serum PFOS is associated with better antihistamine therapy.Study 4: Mechanism of perfluoroalkyl substances in the pathogenesis of CSUObjectives: To investigate the effect of perfluoroalkyl substances(PFASs)on the incidence of urticaria and its possible mechanism.Methods: The effect of PFHp A was evaluated in RBL-2H3 cell cultures and the passive cutaneous anaphylaxis(PCA)model.RBL-2H3 cells were stimulated with different concentrations of PFHp A solution,and the m RNA expression levels of related inflammatory factors and subsequent signal transduction pathways were detected by β-hexosaminidase assay,Real-Time Polymerse Chain Reaction(RT-PCR),and RNA-sequencing(RNA-seq)after activation of RBL-2H3 cells molecular changes.A PCA mouse model was constructed and the expression levels of m RNAs of related inflammatory factors in mice treated with PFASs were detected by formamide extraction,enzyme-linked immunosorbent assay(ELISA),and RT-PCR.Results: PFHp A promoted Ig E-mediated activation of RBL-2H3 cells and the occurrence of passive skin allergic reactions.When the concentration of PFHp A is lower than 250 μM,there was no obvious toxic effect on RBL-2H3 cells.PFHp A promoted the degranulation of RBL-2H3 cells.The m RNA expressions of Th2-type cytokines IL-4 and TNF-αcytokines were increased in the PFHp A-treated cell group compared with the control group.Among the genes that were up-regulated and downregulated by RNA-seq,after verification by RT-PCR,CREM showed a downward trend after PFHp A treatment,and it was statistically significant(P<0.05).In the PCA mouse model,PFHp A and PFBA aggravated the PCA response in mice,and the m RNA expression of the IL-4 cytokine was increased in the mice.Conclusions: PFHp A can promote the degranulation of RBL-2H3 cells and the transcriptional levels of IL-4 and TNF-α.PFHp A may regulate the occurrence of CSU by regulating CREM signaling in the c AMP pathway.