p53 Convergence and Immunity

Renewed interest in Bradykinin and its inactivation, by Angiotensin Converting Enzyme (ACE), during Covid infection reconfirmed RAS and KKS (Kallikrein-Kinin, Bradykinin) as the major systems of vasodilation and constriction contributing to blood pressure and disease. ACE2, a molecule of focus in Covid, reduces the Bradykinin product des-Arg9 bradykinin to inactive metabolites.

In pre-eclampsia reduced Kallikrein (KLK) generation and Bradykinin's activation, via its BK1 and BK2 receptor, modulates stress response through NF-κB and p53 pathways. These are the major cellular stress response pathways that promote or oppose apoptosis and influence cell fate. Two functionally divergent p53-responsive elements were discovered in the rat BK2 receptor promoter, which interact with ACE, play a significant role regulating vascular tone and blood pressure and in the cross-talk between RAS and KKS. 

In uterine immune cells RAS proteins AT1, AT2, and ANP are expressed and ANP co-localizes to uterine Natural Killer (uNK) cells between pregnancy day 10 and 12, immediately before spiral arterial modification. In mice this suggested that uNK contributes to the physiological changes in blood pressure between days 5 and 12.

During the first trimester the uNK cells dramatically increase, from around 15% to 70% of immune cells in the Decidua of the Uterus. Expressed RAS-KKS proteins during this time may be solely responsible for amplified stimulation of the plasma contact system at least via p53-mediated transcription and activation of the BK2 promoter.

In myocytes stretch-mediated release of angiotensin II (AngII) induced apoptosis by activating p53 that enhanced local RAS and decreased the Bcl-2-to-Bax protein ratio in the cell. In endothelial cells mechanical stretch interconnected innate and adaptive immune response in hypertension. This suggests that mechanical forces, such as those experienced in hypertension, can influence the immune system and contribute to inflammation, vascular damage associated with high blood pressure and vascular remodeling.

MYADAM and PRPF31 were the only genes from a meta-analysis that linked diastolic, systolic blood pressure and hypertension. These are located on Chromosome 19 between 50-55,000,000 bps, which includes all Killer immunoglobulin like receptors (KIR's), Kallikrein related peptidases (KLK's) and c19MC MiRNA's, in a region characterized by a 2X background deletion rate. During different trimesters it was found that NK cells, in pre-eclampsia, directly incorporate c19MC MiRNA's that are important to placental development and their deregulation could lead to the development of pre-eclampsia. 

It adds up that the massively disproportionate uNK activity in pregnancy and its impact on the mechanics of blood pressure could amplify sensitivities for p53 mediated stress response. It’s known that uNK cells contribute to the remodeling of spiral arteries and regulation of blood pressure, which are critical for fetal development. Similarly, on a cellular scale, abnormal cell growth and expansion of NK cells, may also amplify conditions that direct NK education and licensing to support growth, as in solid tumors and micro-vascular remodeling, or trigger inflammation, through cytokine expression and/or granulocyte killing of expanded missing-self cells.