Therapeutic Inhibition of Sphingosine Kinase SphK2 lowers Blood Pressure Levels in an Experimental Model of Hypertension by Reducing CD4+ T‐cell Responses

Abstract

Hypertension is a major cause of premature death in the world and the primary contributor to target organ damage. Although many therapeutic strategies to combat hypertension and its comorbidities exist, none of the current anti‐hypertension medications target the immune system, which evolved as key player in the pathogenesis of hypertension. During hypertension, the activation of the immune system links to alterations in sphingosine‐1‐phosphate (S1P) signaling and specifically, to sphingosine kinase 2 (SphK2)‐mediated immune cell chemotaxis. Our previous findings revealed a protection from the development of hypertension in SphK2 knockout mice. In this study, we explored the efficacy of pharmacological SphK2 inhibition to lowering elevated blood pressure and immune activation during angiotensin II‐induced hypertension in mice.In a murine model of hypertension where we treated mice with the SphK2 inhibitor ABC294640 or saline for two weeks, we assessed BP levels using tail cuff plethysmography, immune cell populations using flow cytometry, and circulating S1P levels using mass spectrometry. Using decision trees as a method of supervised machine learning, we set out to identify a sequential set of rules on measurement outcomes, which predict a successful reduction of BP.Pharmacological SphK2 inhibition significantly lowered BP levels, without affecting plasma S1P levels. Notwithstanding its incapacity to lower S1P plasma levels, pharmacological SphK2 inhibition drastically affected T‐cell populations in the blood as evidenced by significantly reduced overall circulating CD4+ T‐cells compared to placebo‐treated hypertensive mice. Besides dampening T‐cell responses typically associated to hypertension (i.e., TH17 and TH1 responses), pharmacological SphK2 inhibition resulted in marked increases of the IL4+TH2 subset. Interestingly, the rules learned by a decision tree identify CD4+ T‐cells as critical modulators for BP responses. Thus, therapeutic administration of CD4 blocking antibody diminished the number of circulating CD4+ T‐cells and significantly lowered elevated blood pressure levels.Our results provide profound evidence that the SphK2‐S1P signaling axis regulates systemic immune cell homeostasis and T‐cell phenotype changes important to blood pressure regulation. Taken together, our work identified first evidence for SphK2 inhibitors as successful immune‐based therapy in hypertension.Support or Funding InformationThis research was supported by the Swedish Research Council (VR 2017‐01243), the Ake Wibergs Stiftelse (M17‐0031), and the Knut & Alice Wallenberg Foundation.