Introduction: Hypertension (HTN) is a global health problem with a prevalence of 32% and is one of the major preventable risk factors for cardiovascular diseases, stroke, and renal failure. Increasing evidence suggest that inflammation, alongside with known contributions of RAAS and sympathicus, also contributes to HTN. The main players in hypertension-related inflammation are monocytes, macrophages, and their effector T-cells. Despite increasing knowledge about hypertension-related inflammation, the molecular mechanisms underlying these processes are not yet fully understood. Recently CRIP1 (Cysteine-rich protein 1) was identified as being deregulated upon changes in blood pressure in human monocytes. CRIP1 is a zinc binding protein and is highly expressed in immune cells as well as in heart and kidney. Recent data showed that monocytic CRIP1 expression is upregulated in a hypertensive murine model, whereas monocyte to macrophage differentiation led to a reduction in CRIP1 expression. However, the molecular function of CRIP1 in immune cells is not known. This study aimed to investigate the impact of CRIP1 on macrophages, focusing specifically on pro(M1)-/anti(M2)-inflammatory macrophages.

Methods: THP-1 cells with stable shRNA-mediated CRIP1 knockdown were used for generation of macrophages (M0, M1, M2) Gene expression was measured by qRT-PCR, and protein expression via flow cytometry. For pro-inflammatory M1-macrophages CD80/CD86, and for anti-inflammatory M2-macrophages Arginase-1 were assessed as markers of the polarization state. To translate findings into a human setting, the correlation between CRIP1 mRNA expressions and immune-related genes were assessed in a transcriptomics dataset (n=1527) of human monocytes of a population-based cohort.

Results: Our experimental data revealed a persistent 60-70% shRNA-mediated downregulation of CRIP1 on mRNA level in all three polarization states (M0/M1/M2). CRIP1 knockdown lead to a significant downregulation of CD80/CD86 (co-activators of T-cell-receptor) in M1-macrophages (60-65% on mRNA level (p<0.01), 42% on protein level (p<0.01)). Furthermore, in M2-macrophages the expression of Arginase-1 was significantly higher in CRIP1 knockdown cells at both mRNA (change 91%, p<0.01) and protein level(change 141%, p<0.01).These data showed that CRIP1 promotes pro-inflammatory and impairs anti-inflammatory macrophage markers. Transcriptomics results from population cohort (normalized for sex, age, systolic blood pressure and BMI) revealed a significant inverse correlation between CD86 and CRIP1 (ß=-0.49,p<0.0001,R²=0.04). However, between CD80 and CRIP1 there was no significant correlation (ß=-0.006,p=0.58,R²=0.001).

Conclusion: Our data provide evidence that CRIP1 influences the polarization states of macrophages. By this, CRIP1 may affect HTN-related inflammation.  CRIP1 might be suitable as a novel prognostic biomarker for monitoring HTN and as a therapeutical target to tackle HTN-related inflammation.