Opposite role of interferon-gamma and interleukin-4 on the regulation of blood pressure in mice

Immune cells and hypertension

Hypertension is one of the leading causes of death due to target organ injury from cardiovascular disease. Although there are many treatments, only one-sixth of hypertensive patients effectively control their blood pressure. Therefore, further understanding the pathogenesis of hypertension is essential for the treatment of hypertension. Much research shows that immune cells play an important role in the pathogenesis of hypertension. Here, we discuss the roles of different immune cells in hypertension. Many immune cells participate in innate and adaptive immune responses, such as monocytes/macrophages, neutrophils, dendritic cells, NK cells, and B and T lymphocytes. Immune cells infiltrate the blood vessels, kidneys, and hearts and cause damage. The mechanism is that immune cells secrete cytokines such as interleukin, interferon, and tumor necrosis factor, which affect the inflammatory reaction, oxidative stress, and kidney sodium water retention, and finally aggravate or reduce the dysfunction, remodeling, and fibrosis of the blood vessel, kidney, and heart to participate in blood pressure regulation. This article reviews the research progress on immune cells and hypertension.

The link between immunity and hypertension in the kidney and heart

Hypertension is the primary cause of cardiovascular disease, which is a leading killer worldwide. Despite the prevalence of this non-communicable disease, still between 90% and 95% of cases are of unknown or multivariate cause ("essential hypertension"). Current therapeutic options focus primarily on lowering blood pressure through decreasing peripheral resistance or reducing fluid volume, but fewer than half of hypertensive patients can reach blood pressure control. Hence, identifying unknown mechanisms causing essential hypertension and designing new treatment accordingly are critically needed for improving public health. In recent years, the immune system has been increasingly implicated in contributing to a plethora of cardiovascular diseases. Many studies have demonstrated the critical role of the immune system in the pathogenesis of hypertension, particularly through pro-inflammatory mechanisms within the kidney and heart, which, eventually, drive a myriad of renal and cardiovascular diseases. However, the precise mechanisms and potential therapeutic targets remain largely unknown. Therefore, identifying which immune players are contributing to local inflammation and characterizing pro-inflammatory molecules and mechanisms involved will provide promising new therapeutic targets that could lower blood pressure and prevent progression from hypertension into renal or cardiac dysfunction.

Interrelationship and Sequencing of Interleukins4, 13, 31, and 33 - An Integrated Systematic Review: Dermatological and Multidisciplinary Perspectives

The interrelations and sequencing of interleukins are complex (inter)actions where each interleukin can stimulate the secretion of its preceding interleukin. In this paper, we attempt to summarize the currently known roles of IL-4, IL-13, IL-31, and IL-33 from a multi-disciplinary perspective. In order to conduct a comprehensive review of the current literature, a search was conducted using PubMed, Google Scholar, Medscape, UpToDate, and Key Elsevier for keywords. The results were compiled from case reports, case series, letters, and literature review papers, and analyzed by a panel of multi-disciplinary specialist physicians for relevance. Based on 173 results, we compiled the following review of interleukin signaling and its clinical significance across a multitude of medical specialties. Interleukins are at the bed rock of a multitude of pathologies across different organ systems and understanding their role will likely lead to novel treatments and better outcomes for our patients. New interleukins are being described, and the role of this inflammatory cascade is still coming to light. We hope this multi-discipline review on the role interleukins play in current pathology assists in this scope.

Interleukin 4: Its Role in Hypertension, Atherosclerosis, Valvular, and Nonvalvular Cardiovascular Diseases

Hypertension is one of the major physiological risk factors for cardiovascular diseases, and it affects more than 1 billion adults worldwide, killing 9 million people every year according to World Health Organization. Also, hypertension is associated with increased risk of kidney disease and stroke. Studying the risk factors that contribute to the pathogenesis of hypertension is key to preventing and controlling hypertension. Numerous laboratories around to globe are very active pursuing research studies to delineate the factors, such as the role of immune system, which could contribute to hypertension. There are studies that were conducted on immune-deficient mice for which experimentally induced hypertension has been ameliorated. Thus, there are possibilities that immune reactivity could be associated with the development of certain type of hypertension. Furthermore, interleukin 4 has been associated with the development of pulmonary hypertension, which could lead to right ventricular remodeling. Also, the immune system is involved in valvular and nonvalvular cardiac remodeling. It has been demonstrated that there is a causative relationship between different interleukins and cardiac fibrosis.

Circulating Th1, Th2, and Th17 Levels in Hypertensive Patients

Background

Evidence from experimental studies showed that Th1, Th2, and Th17 play a pivotal role in hypertension and target organ damage. However, whether changes in the circulating Th1, Th2, and Th17 levels are associated with nondipper hypertension and carotid atherosclerotic plaque in hypertension has yet to be investigated.

Methods

Th1, Th2, and Th17 levels were detected using a flow cytometric analysis, and their related cytokines were measured by enzyme-linked immunosorbent assay in 45 hypertensive patients and 15 normotensive subjects.

Results

The frequencies of Th1 and Th17 in hypertensive patients, especially in nondipper patients and patients with carotid atherosclerotic plaque, were markedly higher than those in the control group; this was accompanied by higher IFN-γ and IL-17 levels. In contrast, the Th2 frequencies and IL-4 levels in hypertensive patients, especially in nondipper patients and patients with carotid atherosclerotic plaque, were significantly lower than those in the control group.

Conclusions

The changes in Th1, Th2, and Th17 activity are associated with the onset of the nondipper type and carotid atherosclerotic plaque in hypertensive patients.

Role of the Immune System in Hypertension

High blood pressure is present in more than one billion adults worldwide and is the most important modifiable risk factor of death resulting from cardiovascular disease. While many factors contribute to the pathogenesis of hypertension, a role of the immune system has been firmly established by a large number of investigations from many laboratories around the world. Immunosuppressive drugs and inhibition of individual cytokines prevent or ameliorate experimental hypertension, and studies in genetically-modified mouse strains have demonstrated that lymphocytes are necessary participants in the development of hypertension and in hypertensive organ injury. Furthermore, immune reactivity may be the driving force of hypertension in autoimmune diseases. Infiltration of immune cells, oxidative stress, and stimulation of the intrarenal angiotensin system are induced by activation of the innate and adaptive immunity. High blood pressure results from the combined effects of inflammation-induced impairment in the pressure natriuresis relationship, dysfunctional vascular relaxation, and overactivity of the sympathetic nervous system. Imbalances between proinflammatory effector responses and anti-inflammatory responses of regulatory T cells to a large extent determine the severity of inflammation. Experimental and human studies have uncovered autoantigens (isoketal-modified proteins and heat shock protein 70) of potential clinical relevance. Further investigations on the immune reactivity in hypertension may result in the identification of new strategies for the treatment of the disease.

Immune Mechanisms in Arterial Hypertension

Traditionally, arterial hypertension and subsequent end-organ damage have been attributed to hemodynamic factors, but increasing evidence indicates that inflammation also contributes to the deleterious consequences of this disease. The immune system has evolved to prevent invasion of foreign organisms and to promote tissue healing after injury. However, this beneficial activity comes at a cost of collateral damage when the immune system overreacts to internal injury, such as prehypertension. Renal inflammation results in injury and impaired urinary sodium excretion, and vascular inflammation leads to endothelial dysfunction, increased vascular resistance, and arterial remodeling and stiffening. Notably, modulation of the immune response can reduce the severity of BP elevation and hypertensive end-organ damage in several animal models. Indeed, recent studies have improved our understanding of how the immune response affects the pathogenesis of arterial hypertension, but the remarkable advances in basic immunology made during the last few years still await translation to the field of hypertension. This review briefly summarizes recent advances in immunity and hypertension as well as hypertensive end-organ damage.

Dual opposing roles of adaptive immunity in hypertension

Hypertension involves remodelling and inflammation of the arterial wall. Interactions between vascular and inflammatory cells play a critical role in disease initiation and progression. T effector and regulatory lymphocytes, members of the adaptive immune system, play contrasting roles in hypertension. Signals from the central nervous system and the innate immune system antigen-presenting cells activate T effector lymphocytes and promote their differentiation towards pro-inflammatory T helper (Th) 1 and Th17 phenotypes. Th1 and Th17 effector cells, via production of pro-inflammatory mediators, participate in the low-grade inflammation that leads to blood pressure elevation and end-organ damage. T regulatory lymphocytes, on the other hand, counteract hypertensive effects by suppressing innate and adaptive immune responses. The present review summarizes and discusses the adaptive immune mechanisms that participate in the pathophysiology in hypertension.

Tumor necrosis factor-alpha: a possible priming agent for the polymorphonuclear leukocyte-reduced nicotinamide-adenine dinucleotide phosphate oxidase in hypertension

In the Sabra rat, oxidative stress (OS) and inflammation precede the development of hypertension. Inhibition of the phagocytic NADPH oxidase attenuates the rise in blood pressure. The present study was set to identify possible priming agents for this enzyme and to test the hypothesis that the phagocytic NADPH oxidase contributes to OS and inflammation. Sabra salt-sensitive and Sabra salt-resistant rats were salt loaded or provided regular chow for 60 days with or without apocynin to inhibit NADPH oxidase. Levels of interleukin 6, tumor necrosis factor-alpha, and interferon-gamma served as indices of inflammation. Extracellular and intracellular levels of the polymorphonuclear leukocyte tumor necrosis factor-alpha receptors (p55 and p75) were assessed by flow cytometry in young and adult rats. NADPH oxidase activity and expression of p47phox were measured in polymorphonuclear leukocytes and aortic rings. Malondialdehyde and carbonylated fibrinogen served as indices of OS. Inflammatory and OS indices excluding interferon-gamma were higher in the hypertensive state and reduced by apocynin. Levels of malondialdehyde and tumor necrosis factor-alpha were elevated already in the prehypertensive state. No differences were found in the levels of p75. The extracellular expression of p55 was higher in adult Sabra salt-resistant compared with Sabra salt-sensitive rats (7.46+/-2.2% versus 2.1+/-0.5%; P<0.05), whereas levels of the intracellular p55 were higher in adult Sabra salt-sensitive rats (3.2+/-2% versus 1.1+/-0.5%; P<0.05). In young normotensive rats, the extracellular levels of p55 were higher in Sabra salt-sensitive compared with Sabra salt-resistant rats (10.6+/-5.2% versus 2.9+/-1.5%; P<0.01). Tumor necrosis factor-alpha plays a role in activation of the polymorphonuclear leukocyte NADPH oxidase, thereby contributing to systemic OS, inflammation, and the development of hypertension in this model.

Nonimmunologic complications and gene polymorphisms of immunoregulatory cytokines in long-term renal transplants

BACKGROUND

While the influence of cytokine gene polymorphisms on immunologic complications after organ transplantation is widely evaluated, little is known about predictive value of cytokine genotype for the development of nonimmunologic post-transplant complications: hypertension, dyslipoproteinemia, diabetes mellitus, hyperuricemia.

METHODS

The -1082IL-10, -308TNF-alpha, transforming growth factor-beta1 (TGF-beta1) (codon 10, 25), -174IL-6, +874IFN-gamma gene single nucleotide polymorphisms (SNP) were studied in 278 long-term renal transplants by polymerase chain reaction-sequence specific primer (PCR-SSP) with respect to nonimmunologic post-transplant complications.

RESULTS

Significant association of the TGF-beta (codon 25) GG genotype with hyperuricemia (P= 0.0013) and dyslipoproteinemia (P= 0.0171) was found. The TGF-beta1 (codon 25) CG genotype was detected more frequently in patients with normal uric acid levels. The +874IFN-gamma AA genotype was associated with type 2/steroid-induced diabetes (P= 0.0127). Frequency of the -1082IL-10 AG genotype was significantly higher in hyperuricemic patients versus controls (P= 0.0022). No associations of polymorphisms in the tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), TGF-beta codon 10 genes with hyperuricemia, dyslipoproteinemia, or diabetes were detected. We failed to observe significant differences in cytokine genotype distribution between hypertensive and normotensive patients.

CONCLUSION

We established an association of particular cytokine genotypes with nonimmunologic post-transplant complications. This supports an idea that assessment of cytokine SNPs may allow more accurate prediction of nonimmunologic complications and appropriate adjustment of pre-emptive treatments in long-term transplant patients.

An ACE inhibitor reduces Th2 cytokines and TGF-beta1 and TGF-beta2 isoforms in murine lupus nephritis

BACKGROUND

Angiotensin-converting enzyme (ACE) inhibitors, such as captopril, are used to control hypertension. In patients and animals with primary nephropathies, these agents improve renal function more than that would be expected from their control of hypertension. Here, we examine the effects of treatment with captopril on lupus nephritis and discuss the potential mechanism(s) by which this agent exerts its renoprotective effects.

METHODS

Lupus-prone, NZB/NZW F1 and MRL-lpr/lpr, mice were treated with captopril or with a control antihypertensive agent, verapamil. Mice were monitored for nephritis, and their sera and tissues analyzed for cytokine and transforming growth factor-beta (TGF-beta) expression.

RESULTS

Captopril treatment delayed the onset of proteinuria when administered to prenephritic mice, whereas verapamil did not. Captopril treatment also retarded disease progression when given to lupus mice that had early disease, and even reversed severe proteinuria in at least some older animals with advanced disease. It reduced chronic renal lesions, but had no effect on autoantibody production. The improvement in renal disease correlated with reduced TGF-beta expression, particularly of the TGF-beta1 and TGF-beta2 isoforms, in the kidneys. Interestingly, in vivo or in vitro exposure to captopril reduced splenic levels of type 2 cytokines, interleukin (IL)-4 and IL-10, suggesting a possible role of the immune system in captopril-mediated disease modulation.

CONCLUSION

Since type 2 cytokines are known to promote lupus glomerulosclerosis, decreased IL-4 and IL-10 production in captopril-treated mice may be related to this agent's renoprotective effects. We argue here that ACE inhibitors not only act as selective TGF-beta inhibitors, but also as selective immunomodulators, to improve lupus nephritis.