Splenectomy increases blood pressure and abolishes sex differences in renal T-regulatory cells in spontaneously hypertensive rats

Sex-Dependency of T Cell-Induced Salt-Sensitive Hypertension and Kidney Damage

BACKGROUND

It is established that the immune system, namely T cells, plays a role in the development of hypertension and renal damage in male Dahl salt-sensitive (SS) rats, but far less is known about this relationship in females. Rats with genetically deleted T cells via CD247 gene mutation on the Dahl SS background (SSCD247-/-) were utilized to interrogate the effect of sex and T cells on salt sensitivity.

METHODS

We assessed the hypertensive and kidney injury phenotypes in male versus female SS and SSCD247-/- rats challenged with 3 weeks of high salt (4.0% NaCl). Differences in T cell activation genes were examined in renal T cells from male and female SS rats, and a sex-specific adoptive transfer was performed by injecting male or female splenocytes into either male or female SSCD247-/- recipients to determine the potential contribution of T cell sex.

RESULTS

The lack of functional T cells in SSCD247-/- rats significantly reduced salt-induced hypertension and proteinuria in both sexes, although SSCD247-/- females exhibited greater protection from kidney damage. Adoptive transfer of either Dahl SS male or female splenocytes into SSCD247-/- male recipients exacerbated hypertension and proteinuria compared with controls, while in SSCD247-/- female recipients, exacerbation of disease occurred only upon transfer of male, but not female, SS splenocytes.

CONCLUSIONS

The absence of T cells in the SSCD247-/- normalized sex differences in blood pressure, though sex differences in renal damage persisted. Splenocyte transfer experiments demonstrated that salt sensitivity is amplified if the sex of the T cell or the recipient is male.

Update on Immune Mechanisms in Hypertension

The contribution of immune cells in the initiation and maintenance of hypertension is undeniable. Several studies have established the association between hypertension, inflammation, and immune cells from the innate and adaptive immune systems. Here, we provide an update to our 2017 American Journal of Hypertension review on the overview of the cellular immune responses involved in hypertension. Further, we discuss the activation of immune cells and their contribution to the pathogenesis of hypertension in different in vivo models. We also highlight existing gaps in the field of hypertension that need attention. The main goal of this review is to provide a knowledge base for translational research to develop therapeutic strategies that can improve cardiovascular health in humans.

Implications of regulatory T cells in non-lymphoid tissue physiology and pathophysiology

Treg cells have been initially described as gatekeepers for the control of autoimmunity, as they can actively suppress the activity of other immune cells. However, their role goes beyond this as Treg cells further control immune responses during infections and tumor development. Furthermore, Treg cells can acquire additional properties for e.g., the control of tissue homeostasis. This is instructed by a specific differentiation program and the acquisition of effector properties unique to Treg cells in non-lymphoid tissues. These tissue Treg cells can further adapt to their tissue environment and acquire distinct functional properties through specific transcription factors activated by a combination of tissue derived factors, including tissue-specific antigens and cytokines. In this review, we will focus on recent findings extending our current understanding of the role and differentiation of these tissue Treg cells. As such we will highlight the importance of tissue Treg cells for tissue maintenance, regeneration, and repair in adipose tissue, muscle, CNS, liver, kidney, reproductive organs, and the lung.