Valentin Nica (1), Medeea Badii (1,2),,Georgiana Cabău (1), Orsolya Gaal (1,2), Andreea-Manuela Mirea (1), Ioana Hotea (3, HINT Consortium, Cristina Pamfil (3), Simona Rednic (3), Radu A. Popp1,Yang Li (2,4), Tania O. Crișan (1,2), Leo A.B. Joosten (1,2)
Affiliation(s):
1. Department of Medical Genetics, UMF “Iuliu Hatieganu”, Cluj-Napoca, Romania
2. Department of Internal Medicine, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands
3. Department of Rheumatology, UMF “Iuliu Hatieganu”, Cluj-Napoca, Romania
4. Helmholtz Centre for Infection Research, Hannover, Germany
Introduction: Gout is one of the most common inflammatory arthritis characterized by deposits of Monosodium Urate crystals in the joint, with an infiltration of neutrophils and macrophages. Circulating monocytes were shown to play a critical role in rheumatic disease, as local inflammation is often driven not by local macrophages, but by differentiated monocytes. Furthermore, gout is preceded by hyperuricemia, which despite being an asymptomatic condition is associated with cardiovascular comorbidities. We performed a bulk RNA-seq analysis of circulating blood cells in volunteers with various level of serum urate and gout patients to identify the signature associated with the two conditions.
Methodology: Peripheral blood was harvested from volunteers and patients with gout and PBMCs were isolated within the first hour. From a subset of the same patients, CD14 monocytes were further isolated. Cells were then stored in TRIzol and RNA-seq analysis was performed. After quality control, a total of 197 PBMC (106 normouricemic, 20 hyperuricemic, 71 gout) samples and 30 CD14 monocyte (15 normouricemic, 15 gout) samples remained. DESeq2 (R) was used to identify Differentially Expressed Genes (DEGs). The analysis was performed both including sex and age as covariates, and separated by sex. Gene set enrichment analysis was performed with fgsea package (R), using a pre-ranked list and Transcription Factor (TF) enrichment analysis was performed with chea3 (web tool).
Findings: We observe a very similar transcriptomic signature in PBMCs when examining asymptomatic hyperuricemic and gout patient samples compared to normouricemic controls, which is further validated in the monocyte dataset. The most consistent DEGs across all datasets are LTF, MMP9, IL1R2, DEFA1B, SLC4A1, CEACAM8 and CYP4F3. The main upregulated pathways were related to the Innate Immune System, Neutrophil Activity and Activation of Matrix Metalloproteinases. The top observed TFs are LTF, GATA1 and CEBPE. Furthermore, when the study groups were split by gender, males showed close to no DEGs in both comparisons, but in females we observe the same signature with higher fold changes. A significant overlap between the examined DEGs and the sex specific signature was observed.
Conclusions: This study shows a proinflammatory phenotype in circulating immune cells that can be observed in some individuals, the number of which is overrepresented in both gout and asymptomatic hyperuricemia. While the cause requires further examination, we provide important insight into the pathophysiology of gout and link hyperuricemia to pathways relevant for other inflammatory diseases such as atherosclerosis. Interestingly, sex-specific differences were observed in line with a bigger change in proinflammatory reprograming in women compared to men, further enforcing the importance of sex-specific analyses in in gout and hyperuricemia.