Resistant Hypertension in the Elderly

Experimental TET2 Clonal Hematopoiesis Predisposes to Renal Hypertension Through an Inflammasome-Mediated Mechanism

BACKGROUND

Hypertension incidence increases with age and represents one of the most prevalent risk factors for cardiovascular disease. Clonal events in the hematopoietic system resulting from somatic mutations in driver genes are prevalent in elderly individuals who lack overt hematologic disorders. This condition is referred to as age-related clonal hematopoiesis (CH), and it is a newly recognized risk factor for cardiovascular disease. It is not known whether CH and hypertension in the elderly are causally related and, if so, what are the mechanistic features.

METHODS

A murine model of adoptive bone marrow transplantation was employed to examine the interplay between Tet2 (ten-eleven translocation methylcytosine dioxygenase 2) clonal hematopoiesis and hypertension.

RESULTS

In this model, a subpressor dose of Ang II (angiotensin II) resulted in elevated systolic and diastolic blood pressure as early as 1 day after challenge. These conditions led to the expansion of Tet2-deficient proinflammatory monocytes and bone marrow progenitor populations. Tet2 deficiency promoted renal CCL5 (C-C motif ligand 5) chemokine expression and macrophage infiltration into the kidney. Consistent with macrophage involvement, Tet2 deficiency in myeloid cells promoted hypertension when mice were treated with a subpressor dose of Ang II. The hematopoietic Tet2-/- condition led to sodium retention, renal inflammasome activation, and elevated levels of IL (interleukin)-1β and IL-18. Analysis of the sodium transporters indicated NCC (sodium-chloride symporter) and NKCC2 (Na+-K+-Cl- cotransporter 2) activation at residues Thr53 and Ser105, respectively. Administration of the NLRP3 (NLR family pyrin domain containing 3) inflammasome inhibitor MCC950 reversed the hypertensive state, sodium retention, and renal transporter activation.

CONCLUSIONS

Tet2-mediated CH sensitizes mice to a hypertensive stimulus. Mechanistically, the expansion of hematopoietic Tet2-deficient cells promotes hypertension due to elevated renal immune cell infiltration and activation of the NLRP3 inflammasome, with consequences on sodium retention. These data indicate that carriers of TET2 CH could be at elevated risk for the development of hypertension and that immune modulators could be useful in treating hypertension in this patient population.

Blood pressure targets, medication consideration and unique concerns in elderly hypertension IV: Focus on frailty, orthostatic hypotension, and resistant hypertension

Hypertension increases the risk of cardiovascular disease in the elderly. Although treating hypertension can reduce the risk of cardiovascular disease and its related mortality, it is also challenging because these patients could have frailty, orthostatic hypotension (OH) and resistant hypertension (RHTN), which makes them more susceptible to treatment-related adverse events. Identifying such patients and tailoring the choice of drugs and blood pressure targets is crucial to balance the harms and benefits. The Clinical Frailty Scale is recommended to assess elderly patients with hypertension and frailty. For very frail patients, unnecessary medications should be deprescribed to avoid adverse events. Hypertension and OH frequently co-occur in the elderly, and recognizing and managing OH is essential to prevent falls and adverse events. The management of blood pressure in elderly patients with frailty, OH, and RHTN is complex, requiring the patients, their family and caregivers to be involved in decision-making to ensure that treatment plans are well-informed and aligned with the patient's needs.

Exposure to ambient air pollution and metabolic kidney diseases: evidence from the Northeast China Biobank

BACKGROUND

At present, there is no epidemiological evidence of the association between metabolic kidney diseases (MKD) and exposure to air pollution.

METHODS

We investigated the association between exposure to long-term air pollution and the risk of developing MKD using samples from the Northeast China Biobank.

RESULTS

Data from 29 191 participants were analyzed. MKD prevalence was 3.23%. Every standard deviation increment in PM2.5 increased the risk of MKD [odds ratio (OR) = 1.37, 95% confidence interval (CI) 1.19-1.58), diabetic kidney disease (DKD) (OR = 2.03, 95% CI 1.52-2.73), hypertensive kidney disease (BKD) (OR = 1.31, 95% CI 1.11-1.56), hyperlipidemic kidney disease (PKD) (OR = 1.39, 95% CI 1.19-1.63) and obese kidney disease (OKD) (OR = 1.34, 95% CI 1.00-1.81). PM10 increased the risk of MKD (OR = 1.42, 95% CI 1.20-1.67), DKD (OR = 1.38, 95% CI 1.03-1.85), BKD (OR = 1.30, 95% CI 1.07-1.58) and PKD (OR = 1.50, 95% CI 1.26-1.80). Sulfur dioxide increased the risk of MKD (OR = 1.57, 95% CI 1.34-1.85), DKD (OR = 1.81, 95% CI 1.36-2.40), BKD (OR = 1.44, 95% CI 1.19-1.74) and PKD (OR = 1.72, 95% CI 1.44-2.04). Ozone decreased the risk of PKD (OR = 0.83, 95% CI 0.70-0.99). Age, ethnicity and air pollution interacted to affect the risk of MKD, BKD and PKD. Associations between air pollution and CKD or metabolic disease were weaker than those with MKD. The association between air pollution and MKD became stronger when compared with participants with non-metabolic disease.

CONCLUSIONS

Air pollution may cause MKD or facilitate the progression from metabolic disease to renal failure.

Inflammation in Salt-Sensitive Hypertension and Renal Damage

PURPOSE OF REVIEW

Low-grade inflammation drives elevations in blood pressure (BP) and consequent target organ damage in diverse experimental models of hypertension. Here, we discuss recent advances elucidating immune-mediated mechanisms of BP elevation and associated target organ damage.

RECENT FINDINGS

Inflammatory mediators produced by immune cells or target organs act on the kidney, vasculature, skin, and nervous system to modulate hypertension. For example, cells of the innate immune system, including monocytes, neutrophils, and dendritic cells (DCs), can all promote BP elevation via actions in the vasculature and kidney. Macrophages expressing VEGF-C impact non-osmotic sodium storage in the skin that in turn regulates salt sensitivity. Within the adaptive immune system, activated T cells can secrete tumor necrosis factor-alpha (TNF-α), interleukin-17a (IL-17a), and interferon-gamma (IFN-γ), each of which has augmented BP and renal damage in pre-clinical models. Inversely, deficiency of IL-17a in mice blunts the hypertensive response and attenuates renal sodium retention via a serum- and glucocorticoid-regulated kinase 1 (SGK1)-dependent pathway. Linking innate and adaptive immune responses, dendritic cells activated by augmented extracellular sodium concentrations stimulate T lymphocytes to produce pro-hypertensive cytokines. By contrast, regulatory T cells (Tregs) can protect against hypertension and associated kidney injury. Rodent studies reveal diverse mechanisms via which cells of the innate and adaptive immune systems drive blood pressure elevation by altering the inflammatory milieu in the kidney, vasculature, and brain.

Hypertension and aging

Hypertension is a highly prevalent condition with numerous health risks, and the incidence of hypertension is greatest among older adults. Traditional discussions of hypertension have largely focused on the risks for cardiovascular disease and associated events. However, there are a number of collateral effects, including risks for dementia, physical disability, and falls/fractures which are increasingly garnering attention in the hypertension literature. Several key mechanisms--including inflammation, oxidative stress, and endothelial dysfunction--are common to biologic aging and hypertension development and appear to have key mechanistic roles in the development of the cardiovascular and collateral risks of late-life hypertension. The objective of the present review is to highlight the multi-dimensional risks of hypertension among older adults and discuss potential strategies for treatment and future areas of research for improving overall care for older adults with hypertension.

Roles of inflammation, oxidative stress, and vascular dysfunction in hypertension

Hypertension is a complex condition and is the most common cardiovascular risk factor, contributing to widespread morbidity and mortality. Approximately 90% of hypertension cases are classified as essential hypertension, where the precise cause is unknown. Hypertension is associated with inflammation; however, whether inflammation is a cause or effect of hypertension is not well understood. The purpose of this review is to describe evidence from human and animal studies that inflammation leads to the development of hypertension, as well as the evidence for involvement of oxidative stress and endothelial dysfunction--both thought to be key steps in the development of hypertension. Other potential proinflammatory conditions that contribute to hypertension-such as activation of the sympathetic nervous system, aging, and elevated aldosterone--are also discussed. Finally, we consider the potential benefit of anti-inflammatory drugs and statins for antihypertensive therapy. The evidence reviewed suggests that inflammation can lead to the development of hypertension and that oxidative stress and endothelial dysfunction are involved in the inflammatory cascade. Aging and aldosterone may also both be involved in inflammation and hypertension. Hence, in the absence of serious side effects, anti-inflammatory drugs could potentially be used to treat hypertension in the future.