Immune modulation of resistance artery remodelling

Vascular remodelling in cardiovascular diseases: hypertension, oxidation, and inflammation

Optimal vascular structure and function are essential for maintaining the physiological functions of the cardiovascular system. Vascular remodelling involves changes in vessel structure, including its size, shape, cellular and molecular composition. These changes result from multiple risk factors and may be compensatory adaptations to sustain blood vessel function. They occur in diverse cardiovascular pathologies, from hypertension to heart failure and atherosclerosis. Dynamic changes in the endothelium, fibroblasts, smooth muscle cells, pericytes or other vascular wall cells underlie remodelling. In addition, immune cells, including macrophages and lymphocytes, may infiltrate vessels and initiate inflammatory signalling. They contribute to a dynamic interplay between cell proliferation, apoptosis, migration, inflammation, and extracellular matrix reorganisation, all critical mechanisms of vascular remodelling. Molecular pathways underlying these processes include growth factors (e.g., vascular endothelial growth factor and platelet-derived growth factor), inflammatory cytokines (e.g., interleukin-1β and tumour necrosis factor-α), reactive oxygen species, and signalling pathways, such as Rho/ROCK, MAPK, and TGF-β/Smad, related to nitric oxide and superoxide biology. MicroRNAs and long noncoding RNAs are crucial epigenetic regulators of gene expression in vascular remodelling. We evaluate these pathways for potential therapeutic targeting from a clinical translational perspective. In summary, vascular remodelling, a coordinated modification of vascular structure and function, is crucial in cardiovascular disease pathology.

Role of plasmacytoid dendritic cells in vascular dysfunction in mice with renovascular hypertension

Endothelial dysfunction and inflammation are clinically significant risk factors for cardiovascular diseases in hypertension. Although immune cells play a role in hypertension, the impact of plasmacytoid dendritic cells in established renovascular hypertension-induced cardiovascular complications is not fully understood. We investigated plasmacytoid dendritic cells' contribution to arterial endothelial dysfunction and inflammation in renovascular hypertension. A two-kidney one-clip (2K1C) model for four weeks in both male and female mice was used to induce renovascular hypertension. We treated mice with or without anti-PDCA-1 antibodies for one week to deplete the plasmacytoid dendritic cells. Renovascular hypertension causes cardiac hypertrophy, lung edema, and microvascular endothelial dysfunction associated with inflammation induction in mice. Moreover, renovascular hypertension affects the profile of immune cells, including dendritic cells and macrophages, with variations between male and female mice. Interestingly, the depletion of plasmacytoid dendritic cells significantly reduces blood pressure, cardiac hypertrophy, lung edema, inflammation, and oxidative stress and improves microvascular endothelial function via the endoplasmic reticulum (ER) stress, autophagy, and mTOR-dependent mechanisms. Plasmacytoid dendritic cells significantly contribute to the development of cardiovascular complications in renovascular hypertension by modulating immune cells, inflammation, oxidative stress, and ER stress.

Immune System and Microvascular Remodeling in Humans

Low-grade inflammatory processes and related oxidative stress may have a key role in the pathogenesis of hypertension and hypertension-mediated organ damage. Innate immune cells, such as neutrophils, dendritic cells, monocytes/macrophages, as well as unconventional T lymphocytes like γδ T cells contribute to hypertension and may trigger vascular inflammation. Adaptive immunity has been demonstrated to participate in elevation of blood pressure and in vascular and kidney injury. In particular, effector T lymphocytes (Th1, Th2, and Th17) may play a relevant role in promoting hypertension and microvascular remodeling, whereas T-regulatory lymphocytes may have a protective role. Effector cytokines produced by these immune cells lead to increased oxidative stress, endothelial dysfunction and contribute to target organ damage in hypertension. A possible role of immune cell subpopulations in the development and regression of microvascular remodeling has also been proposed in humans with hypertension. The present review summarizes the key immune mechanisms that may participate in the pathophysiology of hypertension-mediated inflammation and vascular remodeling; advances in this field may provide the basis for novel therapeutics for hypertension.

Targeting senescent cells for vascular aging and related diseases

Cardiovascular diseases are a serious threat to human health, especially in the elderly. Vascular aging makes people more susceptible to cardiovascular diseases due to significant dysfunction or senescence of vascular cells and maladaptation of vascular structure and function; moreover, vascular aging is currently viewed as a modifiable cardiovascular risk factor. To emphasize the relationship between senescent cells and vascular aging, we first summarize the roles of senescent vascular cells (endothelial cells, smooth muscle cells and immune cells) in the vascular aging process and inducers that contribute to cellular senescence. Then, we present potential strategies for directly targeting senescent cells (senotherapy) or preventively targeting senescence inducers (senoprevention) to delay vascular aging and the development of age-related vascular diseases. Finally, based on recent research, we note some important questions that still need to be addressed in the future.

New progress on the study of aortic stiffness in age-related hypertension

: Hypertension is a worldwide known cause of morbidity and mortality in the elderly and is a major risk factor for cardiovascular complications such as stroke, myocardial infarction, renal complications and heart failure. Although the mechanisms of hypertension remain largely unknown, a recent new concept is that aortic stiffening is a cause of hypertension in middle-aged and older individuals, which highlighted the importance of aortic stiffening in the development of age-related hypertension. Understanding the pathogenesis of aortic stiffness therefore became one of the important approaches to preventing and controlling hypertension. This review discusses the recent progress of the potential causes of aortic stiffening and its implication on the pathogenesis of hypertension, in terms of aging, inflammation, metabolic syndromes, neuroendocrine and the interaction among these causes.

Treg cells depletion is a mechanism that drives microvascular dysfunction in mice with established hypertension

BACKGROUND

Microvascular dysfunction is a major complication in hypertensive patients. We previously reported that CD4⁺CD25⁺ T regulatory cells (Treg) play an important preventive role in hypertension-induced vascular dysfunction. However, whether Treg cells therapy and autophagy inhibition could rescue Treg cells survival and microvascular function in established hypertension is an important question that remained unanswered.

METHODS & RESULTS

Here we showed that Treg cells from mice model of established hypertension displayed an enhanced apoptotic rate, which was rescued with Treg cells transfer and autophagy inhibition. We also showed increased autophagy in mesenteric resistance artery (MRA) in mice with established hypertension. Importantly, the inhibition of autophagy or one single transfer of Treg cells into mice with established hypertension improved the microvascular function independently of high blood pressure. The protection involves the modulation of interleukin-10 (IL-10), inflammation, endoplasmic reticulum (ER) stress, oxidative stress, Akt, and eNOS.

CONCLUSIONS

The present study suggests that Treg cells survival is regulated by autophagy. Also, Treg cells as a cellular therapy aimed at rescuing the microvascular function through an autophagy-dependent mechanism and independently of arterial blood pressure lowering effects. Because our mouse model of established hypertension mimics the clinical situation, our results have the potential for new therapeutic approaches that involve the manipulation of Treg cells and autophagy to overcome established hypertension-induced cardiovascular complications.

Vascular Smooth Muscle Cells and Arterial Stiffening: Relevance in Development, Aging, and Disease

The cushioning function of large arteries encompasses distension during systole and recoil during diastole which transforms pulsatile flow into a steady flow in the microcirculation. Arterial stiffness, the inverse of distensibility, has been implicated in various etiologies of chronic common and monogenic cardiovascular diseases and is a major cause of morbidity and mortality globally. The first components that contribute to arterial stiffening are extracellular matrix (ECM) proteins that support the mechanical load, while the second important components are vascular smooth muscle cells (VSMCs), which not only regulate actomyosin interactions for contraction but mediate also mechanotransduction in cell-ECM homeostasis. Eventually, VSMC plasticity and signaling in both conductance and resistance arteries are highly relevant to the physiology of normal and early vascular aging. This review summarizes current concepts of central pressure and tensile pulsatile circumferential stress as key mechanical determinants of arterial wall remodeling, cell-ECM interactions depending mainly on the architecture of cytoskeletal proteins and focal adhesion, the large/small arteries cross-talk that gives rise to target organ damage, and inflammatory pathways leading to calcification or atherosclerosis. We further speculate on the contribution of cellular stiffness along the arterial tree to vascular wall stiffness. In addition, this review provides the latest advances in the identification of gene variants affecting arterial stiffening. Now that important hemodynamic and molecular mechanisms of arterial stiffness have been elucidated, and the complex interplay between ECM, cells, and sensors identified, further research should study their potential to halt or to reverse the development of arterial stiffness.

Relationship between different subpopulations of circulating CD4+ T lymphocytes and microvascular or systemic oxidative stress in humans

BACKGROUND AND OBJECTIVE

Different components of the immune system, including innate and adaptive immunity (T effector lymphocytes and T regulatory lymphocytes - TREGs) may be involved in the development of hypertension, vascular injury and inflammation. However, no data are presently available in humans about possible relationships between T-lymphocyte subtypes and microvascular oxidative stress. Our objective was to investigate possible relationships between T-lymphocyte subtypes and systemic and microvascular oxidative stress in a population of normotensive subjects and hypertensive patients.

PATIENTS AND METHODS

In the present study we enrolled 24 normotensive subjects and 12 hypertensive patients undergoing an elective surgical intervention. No sign of local or systemic inflammation was present. All patients underwent a biopsy of subcutaneous fat during surgery. A peripheral blood sample was obtained before surgery for assessment of T lymphocyte subpopulations by flow cytometry and circulating indices of oxidative stress.

RESULTS

A significant direct correlation was observed between Th1 lymphocytes and reactive oxygen species (ROS) production (mainly in microvessels). Additionally, significant inverse correlations were observed between ROS and total TREGs, or TREGs subtypes. Significant correlations were detected between circulating indices of oxidative stress/inflammation and indices of microvascular morphology/Th1 and Th17 lymphocytes. In addition, a significant inverse correlation was detected between TREGs in subcutaneous small vessels and C reactive protein.

CONCLUSIONS

Our data suggest that TREG lymphocytes may be protective against microvascular damage, probably because of their anti-oxidant properties, while Th1-Th17 lymphocytes seem to exert an opposite effect, confirming an involvement of adaptive immune system in microvascular damage.

Relationship Between Different Subpopulations of Circulating CD4+ T-lymphocytes and Microvascular Structural Alterations in Humans

BACKGROUND

Different components of the immune system, including innate and adaptive immunity (T-effector lymphocytes and T-regulatory lymphocytes-TREGs) may be involved in the development of hypertension. In addition, it was demonstrated in animal models that TREGs may prevent angiotensin II-induced hypertension and vascular injury/inflammation. However, no data are presently available in humans about possible relationships between T-lymphocyte subtypes and microvascular structural alterations.

METHODS

For this purpose, in the present study, we enrolled 24 normotensive subjects and 12 hypertensive patients undergoing an elective surgical intervention. No sign of local or systemic inflammation was present. All patients underwent a biopsy of subcutaneous fat during surgery. Subcutaneous small resistance arteries were dissected and mounted on a wire myograph and the media to lumen ratio (M/L) was calculated. In addition, retinal arteriolar structure was evaluated noninvasively by scanning laser Doppler flowmetry. Capillary density in the nailfold, dorsum of the finger, and forearm were evaluated by videomicroscopy. A peripheral blood sample was obtained before surgery for assessment of T-lymphocyte subpopulations by flow cytometry.

RESULTS

Significant negative correlations were observed between indices of microvascular structure (M/L of subcutaneous small arteries and wall to lumen ratio of retinal arterioles) and circulating TREG lymphocytes. A direct correlation was observed between M/L of subcutaneous small arteries and circulating Th17 lymphocytes. In addition, total capillary density was correlated with a TREG effector memory subpopulation.

CONCLUSION

Our data suggest that some lymphocyte subpopulations may be related to microvascular remodeling, confirming previous animal data, and opening therapeutic possibilities.

Association Analysis of FOXO3 Longevity Variants With Blood Pressure and Essential Hypertension

BACKGROUND

The minor alleles of 3 FOXO3 single nucleotide polymorphisms (SNPs)- rs2802292 , rs2253310 , and rs2802288 -are associated with human longevity. The aim of the present study was to test these SNPs for association with blood pressure (BP) and essential hypertension (EHT).

METHODS

In a primary study involving Americans of Japanese ancestry drawn from the Family Blood Pressure Program II we genotyped 411 female and 432 male subjects aged 40-79 years and tested for statistical association by contingency table analysis and generalized linear models that included logistic regression adjusting for sibling correlation in the data set. Replication of rs2802292 with EHT was attempted in Japanese SONIC study subjects and of each SNP in a meta-analysis of genome-wide association studies of BP in individuals of European ancestry.

RESULTS

In Americans of Japanese ancestry, women homozygous for the longevity-associated (minor) allele of each FOXO3 SNP had 6mm Hg lower systolic BP and 3mm Hg lower diastolic BP compared with major allele homozygotes (Bonferroni corrected P < 0.05 and >0.05, respectively). Frequencies of minor allele homozygotes were 3.3-3.9% in women with EHT compared with 9.5-9.6% in normotensive women ( P = 0.03-0.04; haplotype analysis P = 0.0002). No association with BP or EHT was evident in males. An association with EHT was seen for the minor allele of rs2802292 in the Japanese SONIC cohort ( P = 0.03), while in European subjects the minor allele of each SNP was associated with higher systolic and diastolic BP.

CONCLUSION

Longevity-associated FOXO3 variants may be associated with lower BP and EHT in Japanese women.

The structural factor of hypertension: large and small artery alterations

Pathophysiological studies have extensively investigated the structural factor in hypertension, including large and small artery remodeling and functional changes. Here, we review the recent literature on the alterations in small and large arteries in hypertension. We discuss the possible mechanisms underlying these abnormalities and we explain how they accompany and often precede hypertension. Finally, we propose an integrated pathophysiological approach to better understand how the cross-talk between large and small artery changes interacts in pressure wave transmission, exaggerates cardiac, brain and kidney damage, and lead to cardiovascular and renal complications. We focus on patients with essential hypertension because this is the most prevalent form of hypertension, and describe other forms of hypertension only for contrasting their characteristics with those of uncomplicated essential hypertension.

Role of mineralocorticoid receptor antagonists in cardiovascular disease

Aldosterone exerts its best known sodium homeostasis actions by controlling sodium excretion at the level of the distal tubules via activation of the apical epithelial sodium channel and the basolateral Na(+)/K(+)ATPase pump. Recently, this mineralocorticoid hormone has been demonstrated to act on the heart and blood vessels. Excess release of aldosterone in relation to the salt status induces both genomic and nongenomic effects that by promoting endothelial dysfunction, and vascular and cardiorenal adverse remodeling, contribute to the target organ damage found in hypertension, heart failure, myocardial infarction, and chronic renal failure. Mineralocorticoid receptor blockers have been shown to be highly effective in resistant hypertension and to slow down heart failure progression, and in experimental animals, the development of atherosclerosis. Blockade of the action of aldosterone and potentially other mineralocorticoid steroids has been increasingly demonstrated to be an extremely beneficial therapy in different forms of cardiovascular disease. This review provides a summary of the knowledge that exists on aldosterone actions in the cardiovascular system and, in providing the translational impact of this knowledge to the clinical arena, illustrates how much more needs to be achieved in exploring the use of mineralocorticoid receptor blockers in less advanced stages of heart, renal, and vascular disease.

Mineralocorticoid receptors in immune cells: emerging role in cardiovascular disease

Mineralocorticoid receptors (MRs) contribute to the pathophysiology of hypertension and cardiovascular disease in humans. As such, MR antagonists improve cardiovascular outcomes but the molecular mechanisms remain unclear. The actions of the MR in the kidney to increase blood pressure are well known, but the recent identification of MRs in immune cells has led to novel discoveries in the pathogenesis of cardiovascular disease that are reviewed here. MR regulates macrophage activation to the pro-inflammatory M1 phenotype and this process contributes to the pathogenesis of cardiovascular fibrosis in response to hypertension and to outcomes in mouse models of stroke. T lymphocytes have recently been implicated in the development of hypertension and cardiovascular fibrosis in mouse models. MR activation in vivo promotes T lymphocyte differentiation to the pro-inflammatory Th1 and Th17 subsets while decreasing the number of anti-inflammatory T regulatory lymphocytes. The mechanism likely involves activation of MR in antigen presenting dendritic cells that subsequently regulate Th1/Th17 polarization by production of cytokines. Alteration of the balance between T helper and T regulatory lymphocytes contributes to the pathogenesis of hypertension and atherosclerosis and the associated complications. B lymphocytes also express the MR and specific B lymphocyte-derived antibodies modulate the progression of atherosclerosis. However, the role of MR in B lymphocyte function remains to be explored. Overall, recent studies of MR in immune cells have identified new mechanisms by which MR activation may contribute to the pathogenesis of organ damage in patients with cardiovascular risk factors. Conversely, inhibition of leukocyte MR may contribute to the protective effects of MR antagonist drugs in cardiovascular patients. Further understanding of the role of MR in leukocyte function could yield novel drug targets for cardiovascular disease.

Complete blood count and retinal vessel calibers

Objective

The influence of hematological indices such as complete blood count on microcirculation is poorly understood. Retinal microvasculature can be directly visualized and vessel calibers are associated with a range of ocular and systemic diseases. We examined the association of complete blood count with retinal vessel calibers.

Methods

Cross-sectional population-based Blue Mountains Eye Study, n = 3009, aged 49+ years. Complete blood count was measured from fasting blood samples taken at baseline examination, 1992–4. Retinal arteriolar and venular calibers were measured from digitized retinal photographs using a validated semi-automated computer program.

Results

All analyses adjusted for age, sex, systolic blood pressure, diabetes, smoking and fellow vessel caliber. Higher hematocrit, white cell count and platelet count were associated with narrower arteriolar caliber (p = 0.02, 0.03 and 0.001 respectively), while higher hemoglobin, hematocrit, red cell count, white cell count and platelet count were associated with wider venular caliber (p<0.0001 for all). Each quintile increase in hematocrit, white cell count and platelet count was associated with approximately 0.5 µm narrower arteriolar caliber; whereas each quintile increase in all of the complete blood count components was associated with approximately 1–2 µm wider venular caliber.

Conclusions

These associations show that elevated levels of hematological indices can have adverse effects on the microcirculation.