Autoantibodies against arterial antigens: characterization by ELISA and immunoblot analysis in the spontaneously hypertensive rat

Adaptive Immunity in Hypertension

PURPOSE OF REVIEW

In recent years, a vast body of evidence has accumulated indicating the role of the immune system in the regulation of blood pressure and modulation of hypertensive pathology. Numerous cells of the immune system, both innate and adaptive immunity, have been indicated to play an important role in the development and maintenance of hypertension. The purpose of this review was to summarize the role of adaptive immunity in experimental models of hypertension (genetic, salt-sensitive, and Angiotensin (Ang) II induced) and in human studies. In particular, the role of T and B cells is discussed.

RECENT FINDINGS

In response to hypertensive stimuli such as Ang II and high salt, T cells become pro-inflammatory and they infiltrate the brain, blood vessel adventitia and periadventitial fat, heart, and the kidney. Pro-inflammatory T cell-derived cytokines such as IFN-γ and TNF-α (from CD8+ and CD4+Th1) and IL-17A (from the γδ-T cell and CD4+Th17) exacerbate hypertensive responses mediating both endothelial dysfunction and cardiac, renal, and neurodegenerative injury. The modulation of adaptive immune activation in hypertension has been attributed to target organ oxidative stress that leads to the generation of neoantigens, including isolevuglandin-modified proteins. The role of adaptive immunity is sex-specific with much more pronounced mechanisms in males than that in females. Hypertension is also associated with B cell activation and production of autoantibodies (anti-Hsp70, anti-Hsp65, anti-Hsp60, anti-AT1R, anti-α1AR, and anti-β1AR). The hypertensive responses can be inhibited by T regulatory lymphocytes (Tregs) and their anti-inflammatory IL-10. Adaptive immunity and its interface with innate mechanisms may represent valuable targets in the modulation of blood pressure, as well as hypertension-related residual risk.

Recent Advances in Immunity and Hypertension

Persistent immune system activation plays an important role in the development of various forms of hypertension. Activation of the innate immune system, inflammation, and subsequent adaptive immune system response causing end-organ injury and dysfunction ultimately leads to hypertension and its associated sequelae including coronary artery disease, heart failure, stroke, and chronic kidney disease. In this review, we will provide updates on the innate and adaptive immune cells involved in hypertension, the current understanding of how the immune system gets activated, and examine the recently discovered mechanisms involved in several forms of experimental hypertension.

Autoimmune therapeutic chloroquine lowers blood pressure and improves endothelial function in spontaneously hypertensive rats

It has been suggested that hypertension results from a loss of immunological tolerance and the resulting autoimmunity may be an important underlying factor of its pathogenesis. This stems from the observations that many of the features involved in autoimmunity are also implicated in hypertension. Furthermore, the underlying presence of hypertension and cardiovascular disease are frequently observed in patients with autoimmune diseases. Antimalarial agents such as chloroquine are generally among the first line treatment options for patients with autoimmune diseases; however, whether they can improve a hypertensive phenotype in a genetic model of essential hypertension remains to be clarified. Therefore, we hypothesized that chloroquine treatment would improve endothelial function and lower blood pressure in spontaneously hypertensive rats (SHR). We treated adult SHR and Wistar-Kyoto rats (12 weeks old), as well as a group of young SHR (5 weeks old), with chloroquine (40mg/kg/day via intraperitoneal injection) for 21 days. Chloroquine lowered blood pressure in adult SHR, but did not impede the development of high blood pressure in young SHR. In isolated mesenteric resistance arteries from SHR of both ages, chloroquine treatment inhibited cyclooxygenase-dependent contraction to acetylcholine, lowered vascular and systemic generation of reactive oxygen species, and improved nitric oxide bioavailability. Overall, these data reveal the anti-hypertensive mechanisms of chloroquine in the vasculature, which may be important for lowering risk of cardiovascular disease in patients with autoimmune diseases. Furthermore, it adds to the growing body of evidence suggesting that autoimmunity underlies hypertension.