SAT0119 PARADOXICAL NEUTROPHIL ACTIVATION BY ANTI-IL6 THERAPY: TRANSCRIPTOME ANALYSIS SHOWS A RATIONALE FOR DERMATOLOGICAL ADVERSE REACTIONS AND DECREASED NEUTROPHIL COUNTS AFTER TOCILIZUMAB TREATMENT

Abstract

Background:Skin rashes as a side effect of Tocilizumab therapy (TCZ- Tx) has not been paid much attention, because the incidence was only 1~2% in the drug information sheets. However, we experienced several RA cases with development of various skin rashes associated with neutrophil activation after TCZ-Tx. On the other hand, it is well known that the neutrophil counts in peripheral blood decreases after TCZ-Tx, whereas it does not affect the rate of serious infections. The detailed mechanism is still unclear.Objectives:To detect the characteristics of the changes in gene expressions of peripheral blood associated with TCZ-Tx and the development of skin rashes as its side effect.Methods:Total of 14 RA patients with TCZ-Tx were included. Among them, 4 patients developed TCZ-related rashes (group S) and 10 patients did not show any side effects (group C). Peripheral whole blood at just before (pre) and 3 months after (post) TCZ-Tx from each patient were subjected to the analysis. Total RNAs were extracted with PAXgene miRNA kit and analyzed with next-generation sequencing. First, group C was investigated for the normal response to TCZ-Tx. Differentially expressed genes (DEGs) were selected by paired comparison (post vs. pre). And then, enrichment analysis using gene ontology (GO) terms were performed. Second, to explore the characteristics of group S, all expressed genes in 14 cases at just before TCZ-Tx were subjected to a hierarchical clustering analysis. The DEGs (group S vs. C and post vs. pre) were also investigated with weighted gene co-expression network analysis (WGCNA) and GO analysis. Meanwhile, the total eigengene expressions of the important modules identified by WGCNA in each cases were also calculated.Results:Surprisingly, 8 out of the top 10 enriched GO terms in the up-regulated genes were relevant to leukocyte activation such as ‘neutrophil migration” by the analysis of DEGs (post vs. pre) in group C. The cluster analysis of ‘pre’ genes confirmed that the patterns of gene expression between group S and C was different. WGCNA analysis of DEGs (group S vs. C) revealed that genes related to acute inflammation such as ‘leukocyte mediated immunity’ were activated in group S. Interestingly, it was not correlated with disease activity score (DAS) of RA. By the analysis of DEGs (post vs. pre) of upregulated genes, we found that the total eigengene expressions of the module enriched with genes related to ‘cell adhesion’ or ‘leukocyte migration’ were significantly increased in all cases of group S.Conclusion:This is the first evidence that the genes associated with neutrophil migration is significantly activated after TCZ-Tx. It is noteworthy that the gene activation was observed in cases without any side effects. The decreased neutrophil counts in peripheral blood have been known after initiation of TCZ-Tx, which did not affect the rate of serious infections. Recently, It was reported that TCZ affects neutrophil trafficking to the bone marrow1). Our findings will provide a rationale for its cause. On the other hand, we experienced several RA cases with development of various skin rashes associated with neutrophil activation after TCZ-Tx. However, majority of patients do not develop the side effect, even though genes related to ‘neutrophil migration’ are activated. In group S, our findings indicate that the genes related to ‘leukocyte mediated immunity’ was already activated at the initiation of treatment without correlating to DAS of RA, furthermore, the gene upregulation related to ‘leukocyte migration’ was more prominent after TCZ-Tx. Although it is difficult to predict the patients developing skin rashes before TCZ-Tx, we do not recommend to use TCZ for the patients with neutrophilic dermatosis which is often associated with RA.