Deficiency of Complement C3a and C5a receptors Does Not Prevent Angiotensin II-Induced Hypertension and Hypertensive End-Organ Damage

BACKGROUND

Complement may drive the pathology of hypertension through effects on innate and adaptive immune responses. Recently an injurious role for the anaphylatoxin receptors C3aR (complement component 3a receptor) and C5aR1 (complement component 5a receptor) in the development of hypertension was shown through downregulation of Foxp3+ (forkhead box protein 3) regulatory T cells. Here, we deepen our understanding of the therapeutic potential of targeting both receptors in hypertension.

METHODS

Data from the European Renal cDNA Bank, single cell sequencing and immunohistochemistry were examined in hypertensive patients. The effect of C3aR or C3aR/C5aR1 double deficiency was assessed in two models of Ang II (angiotensin II)-induced hypertension in knockout mice.

RESULTS

We found increased expression of C3aR, C5aR1 and Foxp3 cells in kidney biopsies of patients with hypertensive nephropathy. Expression of both receptors was mainly found in myeloid cells. No differences in blood pressure, renal injury (albuminuria, glomerular filtration rate, glomerular and tubulointerstitial injury, inflammation) or cardiac injury (cardiac fibrosis, heart weight, gene expression) between control and mutant mice was discerned in C3aR-/- as well as C3aR/C5aR1-/- double knockout mice. The number of renal Tregs was not decreased in Ang II as well as in DOCA salt induced hypertension.

CONCLUSIONS

Hypertensive nephropathy in mice and men is characterized by an increase of renal regulatory T cells and enhanced expression of anaphylatoxin receptors. Our investigations do not corroborate a role for C3aR/C5aR1 axis in Ang II-induced hypertension hence challenging the concept of anaphylatoxin receptor targeting in the treatment of hypertensive disease.

Increased blood pressure after nonsevere COVID-19

BACKGROUND

Various sequelae have been described after nonsevere coronavirus disease 2019 (COVID-19), but knowledge on postacute effects on blood pressure is limited.

METHODS

This is a cross-sectional analysis of blood pressure profiles in individuals after nonsevere COVID-19 compared with matched population-based individuals without prior COVID-19. Data were derived from the ongoing and prospective Hamburg City Health Study, a population-based study in Hamburg, Germany, and its associated COVID-19 program, which included individuals at least 4 months after COVID-19. Matching was performed by age, sex, education, and preexisting hypertension in a 1 : 4 ratio.

RESULTS

Four hundred and thirty-two individuals after COVID-19 (mean age 56.1 years) were matched to 1728 controls without prior COVID-19 (56.2 years). About 92.8% of COVID-19 courses were mild or moderate, only 7.2% were hospitalized, and no individual had been treated on an intensive care unit. Even after adjustment for relevant competing risk factors, DBP [+4.7 mmHg, 95% confidence interval (95% CI) 3.97-5.7, P  < 0.001] was significantly higher in individuals after COVID-19. For SBP, a trend towards increased values was observed (+1.4 mmHg, 95% CI -0.4 to 3.2, P  = 0.120). Hypertensive blood pressures at least 130/80 mmHg (according to the ACC/AHA guideline) and at least 140/90 mmHg (ESC/ESH guideline) occurred significantly more often in individuals after COVID-19 than matched controls (odds ratio 2.0, 95% CI 1.5-2.7, P  < 0.001 and odds ratio 1.6, 95% CI 1.3-2.0, P  < 0.001, respectively), mainly driven by changes in DBP.

CONCLUSION

Blood pressure is higher in individuals after nonsevere COVID-19 compared with uninfected individuals suggesting a significant hypertensive sequela.

Left ventricular myocardial strain responding to chronic pressure overload in patients with resistant hypertension evaluated by feature-tracking CMR

OBJECTIVES

The study aimed to investigate the alterations of myocardial deformation responding to long-standing pressure overload and the effects of focal myocardial fibrosis using feature-tracking cardiac magnetic resonance (FT-CMR) in patients with resistant hypertension (RH).

METHODS

Consecutive RH patients were prospectively recruited and underwent CMR at a single institution. FT-CMR analyses based on cine images were applied to measure left ventricular (LV) peak systolic global longitudinal (GLS), radial (GRS), and circumferential strain (GCS). Functional and morphological CMR variables, and late gadolinium enhancement (LGE) imaging were also obtained.

RESULTS

A total of 50 RH patients (63 ± 12 years, 32 men) and 18 normotensive controls (57 ± 8 years, 12 men) were studied. RH patients had a higher average systolic blood pressure than controls (166 ± 21 mmHg vs. 116 ± 8 mmHg, p < 0.001) with the intake of 5 ± 1 antihypertensive drugs. RH patients showed increased LV mass index (78 ± 15 g/m2 vs. 61 ± 9 g/m2, p < 0.001), decreased GLS (- 16 ± 3% vs. - 19 ± 2%, p = 0.001) and GRS (41 ± 12% vs. 48 ± 8%, p = 0.037), and GCS was reduced by trend (- 17 ± 4% vs. - 19 ± 4%, p = 0.078). Twenty-one (42%) RH patients demonstrated a LV focal myocardial fibrosis (LGE +). LGE + RH patients had higher LV mass index (85 ± 14 g/m2 vs. 73 ± 15 g/m2, p = 0.007) and attenuated GRS (37 ± 12% vs. 44 ± 12%, p = 0.048) compared to LGE - RH patients, whereas GLS (p = 0.146) and GCS (p = 0.961) were similar.

CONCLUSION

Attenuation of LV GLS and GRS, and GCS decline by tendency, might be adaptative changes responding to chronic pressure overload. There is a high incidence of focal myocardial fibrosis in RH patients, which is associated with reduced LV GRS.

CLINICAL RELEVANCE STATEMENT

Feature-tracking CMR-derived myocardial strain offers insights into the influence of long-standing pressure overload and of a myocardial fibrotic process on cardiac deformation in patients with resistant hypertension.

KEY POINTS

• Variations of left ventricular strain are attributable to the degree of myocardial impairment in resistant hypertensive patients. • Focal myocardial fibrosis of the left ventricle is associated with attenuated global radial strain. • Feature-tracking CMR provides additional information on the attenuation of myocardial deformation responding to long-standing high blood pressure.

Complement component C3 as a new target to lower albuminuria in hypertensive kidney disease

BACKGROUND AND PURPOSE

Complement activation may drive hypertension through its effects on immunity and tissue integrity.

EXPERIMENTAL APPROACH

We examined expression of C3, the central protein of the complement cascade, in hypertension.

KEY RESULTS

Increased C3 expression was found in kidney biopsies and micro-dissected glomeruli of patients with hypertensive nephropathy. Renal single cell RNA sequence data from normotensive and hypertensive patients confirmed expression of C3 in different cellular compartments of the kidney. In angiotensin II (Ang II) induced hypertension renal C3 expression was up-regulated. C3-/- mice revealed a significant lower albuminuria in the early phase of hypertension. However, no difference was found for blood pressure, renal injury (histology, glomerular filtration rate, inflammation) and cardiac injury (fibrosis, weight, gene expression) between C3-/- and wildtype mice after Ang II infusion. Also, in deoxycorticosterone acetate (DOCA) salt hypertension, a significantly lower albuminuria was found in the first weeks of hypertension in C3 deficient mice but no significant difference in renal and cardiac injury. Down-regulation of C3 by C3 targeting GalNAc (n-acetylgalactosamine) small interfering RNA (siRNA) conjugate decreased C3 in the liver by 96% and lowered albuminuria in the early phase but showed no effect on blood pressure and end-organ damage. Inhibition of complement C5 by siRNA showed no effect on albuminuria.

CONCLUSION AND IMPLICATIONS

Increased C3 expression is found in the kidneys of hypertensive mice and men. Genetic and therapeutic knockdown of C3 improved albuminuria in the early phase of hypertension but did not ameliorate arterial blood pressure nor renal and cardiac injury.

CD4+ T cells produce GM-CSF and drive immune-mediated glomerular disease by licensing monocyte-derived cells to produce MMP12

GM-CSF in glomerulonephritisDespite glomerulonephritis being an immune-mediated disease, the contributions of individual immune cell types are not clear. To address this gap in knowledge, Paust et al. characterized pathological immune cells in samples from patients with glomerulonephritis and in samples from mice with the disease. The authors found that CD4+ T cells producing granulocyte-macrophage colony-stimulating factor (GM-CSF) licensed monocytes to promote disease by producing matrix metalloproteinase 12 and disrupting the glomerular basement membrane. Targeting GM-CSF to inhibit this axis reduced disease severity in mice, implicating this cytokine as a potential therapeutic target for patients with glomerulonephritis. -CM.

Glucocorticoids target the CXCL9/CXCL10-CXCR3 axis and confer protection against immune-mediated kidney injury

Glucocorticoids remain a cornerstone of therapeutic regimes for autoimmune and chronic inflammatory diseases - for example, in different forms of crescentic glomerulonephritis - because of their rapid antiinflammatory effects, low cost, and wide availability. Despite their routine use for decades, the underlying cellular mechanisms by which steroids exert their therapeutic effects need to be fully elucidated. Here, we demonstrate that high-dose steroid treatment rapidly reduced the number of proinflammatory CXCR3+CD4+ T cells in the kidney by combining high-dimensional single-cell and morphological analyses of kidney biopsies from patients with antineutrophil cytoplasmic antibody-associated (ANCA-associated) crescentic glomerulonephritis. Using an experimental model of crescentic glomerulonephritis, we show that the steroid-induced decrease in renal CD4+ T cells is a consequence of reduced T cell recruitment, which is associated with an ameliorated disease course. Mechanistic in vivo and in vitro studies revealed that steroids act directly on renal tissue cells, such as tubular epithelial cells, but not on T cells, which resulted in an abolished renal expression of CXCL9 and CXCL10 as well as in the prevention of CXCR3+CD4+ T cell recruitment to the inflamed kidneys. Thus, we identified the CXCL9/CXCL10-CXCR3 axis as a previously unrecognized cellular and molecular target of glucocorticoids providing protection from immune-mediated pathology.

Mosaic theory revised: inflammation and salt play central roles in arterial hypertension

The mosaic theory of hypertension was advocated by Irvine Page ~80 years ago and suggested that hypertension resulted from the close interactions of different causes. Increasing evidence indicates that hypertension and hypertensive end-organ damage are not only mediated by the proposed mechanisms that result in hemodynamic injury. Inflammation plays an important role in the pathophysiology and contributes to the deleterious consequences of arterial hypertension. Sodium intake is indispensable for normal body function but can be detrimental when it exceeds dietary requirements. Recent data show that sodium levels also modulate the function of monocytes/macrophages, dendritic cells, and different T-cell subsets. Some of these effects are mediated by changes in the microbiome and metabolome due to high-salt intake. The purpose of this review is to propose a revised and extended version of the mosaic theory by summarizing and integrating recent advances in salt, immunity, and hypertension research. Salt and inflammation are placed in the middle of the mosaic because both factors influence each of the remaining pieces.

The role of the mineralocorticoid receptor in immune cells in in cardiovascular disease

Chronic low-grade inflammation and immune cell activation are important mechanisms in the pathophysiology of cardiovascular disease (CVD). Therefore, targeted immunosuppression is a promising novel therapy to lower cardiovascular risk. In this review, we identify the mineralocorticoid receptor (MR) on immune cells as a potential target to modulate inflammation. The MR is present in almost all cells of the cardiovascular system, including immune cells. Activation of the MR in innate and adaptive immune cells induces inflammation which can contribute to CVD, by inducing endothelial dysfunction and hypertension. Moreover, it accelerates atherosclerotic plaque formation and destabilization and impairs tissue regeneration after ischemic events. Identifying the molecular targets for these non-renal actions of the MR provide promising novel cardiovascular drug targets for mineralocorticoid receptor antagonists (MRAs), which are currently mainly applied in hypertension and heart failure.

The role of complement in arterial hypertension and hypertensive end organ damage

Increasing evidence indicates that hypertension and hypertensive end organ damage are not only mediated by haemodynamic injury but that inflammation also plays an important role. The complement system protects the host from a hostile microbial environment and maintains tissue and cell integrity through the elimination of altered or dead cells. As an important effector arm of innate immunity, it plays also central roles in the regulation of adaptive immunity. Thus, complement activation may drive the pathology of hypertension through its effects on innate and adaptive immune responses, aside from direct effects on the vasculature. Recent experimental data strongly support a role for complement in all stages of arterial hypertension. The remarkably similar clinical and histopathological features of malignant nephrosclerosis and atypical haemolytic uraemic syndrome suggest also a role for complement in the development of malignant nephrosclerosis. Here, we review the role of complement in hypertension and hypertensive end organ damage. LINKED ARTICLES: This article is part of a themed issue on Canonical and non-canonical functions of the complement system in health and disease. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.14/issuetoc.

Immune mechanisms in arterial hypertension. Recent advances

Increasing evidence indicates that hypertension and hypertensive end-organ damage are not only mediated by hemodynamic injury. Inflammation also plays an important role in the pathophysiology and contributes to the deleterious consequences of this disease. Cells of the innate immune system including monocyte/macrophages and dendritic cells can promote blood pressure elevation via effects mostly on kidney and vascular function. Moreover, convincing evidence shows that T and B cells from the adaptive immune system are involved in hypertension and hypertensive end-organ damage. Skin monocyte/macrophages, regulatory T cells, natural killer T cells, and myeloid-derived suppressor cells have been shown to exert blood pressure controlling effects. Sodium intake is undoubtedly indispensable for normal body function but can be detrimental when taken in excess of dietary requirements. Sodium levels also modulate the function of monocyte/macrophages, dendritic cells, and different T cell subsets. Some of these effects are mediated by changes in the microbiome and metabolome that can be found after high salt intake. Modulation of the immune response can reduce severity of blood pressure elevation and hypertensive end-organ damage in several animal models. The purpose of this review is to briefly summarize recent advances in immunity and hypertension as well as hypertensive end-organ damage.

B6.Rag1 Knockout Mice Generated at the Jackson Laboratory in 2009 Show a Robust Wild-Type Hypertensive Phenotype in Response to Ang II (Angiotensin II)

A key finding supporting a causal role of the immune system in the pathogenesis of hypertension is the observation that RAG1 knockout mice on a C57Bl/6J background (B6.Rag1^-/-), which lack functional B and T cells, develop a much milder hypertensive response to Ang II (angiotensin II) than control C57Bl/6J mice. Here, we report that we never observed any Ang II resistance of B6.Rag1^-/- mice purchased directly from the Jackson Laboratory as early as 2009. B6.Rag1^-/- mice displayed nearly identical blood pressure increases monitored via radiotelemetry and hypertensive end-organ damage in response to different doses of Ang II and different levels of salt intake (0.02%, 0.3%, and 3% NaCl diet). Similarly, restoration of T-cell immunity by adoptive cell transfer did not affect the blood pressure response to Ang II in B6.Rag1^-/- mice. Full development of the hypertension-resistant phenotype in B6.Rag1^-/- mice appears to depend on the action of yet unidentified nongenetic modifiers in addition to the absence of functional T cells.

Adaptive immunity and IL-17A are not involved in the progression of chronic kidney disease after 5/6 nephrectomy in mice

BACKGROUND AND PURPOSE

The adaptive immune response and IL-17A contribute to renal damage in several experimental models of renal injury.

EXPERIMENTAL APPROACH

To evaluate the role of the adaptive immune response, 5/6 nephrectomy was performed in wildtype DBA/1J mice and in recombination-activating gene-1 (RAG-1) deficient mice that lack B and T-cells. To assess the role of IL-17A, we carried out 5/6 nephrectomy in IL-17A deficient mice. Flow cytometric analysis, immunohistochemistry and RT-PCR were used.

KEY RESULTS

Infiltration of CD3⁺ T-cells in the remnant kidney was increased after 5/6 nephrectomy in wildtype mice, along with a robust induction of IL-17A production in CD4⁺ T and γδ T-cells. After 5/6 nephrectomy, wildtype mice developed albuminuria in the nephrotic range over 10 weeks. This was accompanied by severe glomerular sclerosis and tubulointerstitial injury, and as well as renal mRNA expression of markers of inflammation and fibrosis (the chemokine CCL2, plasminogen activator inhibitor-1; PAI-1 and neutrophil gelatinase-associated lipocalin; NGAL). Unexpectedly, RAG-1 deficient mice and IL-17A deficient mice developed renal injury, similar to that in wildtype mice. No differences were found for albuminuria, glomerular sclerosis, tubulointerstitial injury and mRNA expression of CCL2, PAI-1 and NGAL. Mortality did not differ between the three groups.

CONCLUSIONS AND IMPLICATIONS

Numbers of CD3⁺ T-cells and IL-17A⁺ lymphocytes infiltrating the kidney were increased after 5/6 nephrectomy. In contrast to other experimental models of renal injury, genetic deficiency of the adaptive immune system or of IL-17A did not attenuate induction or progression of chronic kidney disease after 5/6 nephrectomy.

LINKED ARTICLES

This article is part of a themed section on Immune Targets in Hypertension. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.12/issuetoc.

The chemokine receptor CX3CR1 reduces renal injury in mice with angiotensin II-induced hypertension

The role of CX₃CR1, also known as fractalkine receptor, in hypertension is unknown. The present study determined the role of the fractalkine receptor CX₃CR1 in hypertensive renal and cardiac injury. Expression of CX₃CR1 was determined using CX₃CR1^GFP/+ mice that express a green fluorescent protein (GFP) reporter in CX₃CR1⁺ cells. FACS analysis of leukocytes isolated from the kidney showed that 34% of CD45⁺ cells expressed CX₃CR1. Dendritic cells were the majority of positive cells (67%) followed by macrophages (10%), NK cells (6%), and T cells (10%). With the use of confocal microscopy, the receptor was detected in the kidney only on infiltrating cells but not on resident renal cells. To evaluate the role of CX₃CR1 in hypertensive end-organ injury, an aggravated model of hypertension was used. Unilateral nephrectomy was performed followed by infusion of angiotensin II (ANG II, 1.5 ng·g^-1·min^-1) and a high-salt diet in wild-type ( n = 15) and CX₃CR1-deficient mice ( n = 18). CX₃CR1 deficiency reduced the number of renal dendritic cells and increased the numbers of renal CD11b/F4/80⁺ macrophages and CD11b/Ly6G⁺ neutrophils in ANG II-infused mice. Surprisingly, CX₃CR1-deficient mice exhibited increased albuminuria, glomerular injury, and reduced podocyte density in spite of similar levels of arterial hypertension. In contrast, cardiac damage as assessed by increased heart weight, cardiac fibrosis, and expression of fetal genes, and matrix components were not different between both genotypes. Our findings suggest that CX₃CR1 exerts protective properties by modulating the invasion of inflammatory cells in hypertensive renal injury. CX₃CR1 inhibition should be avoided in hypertension because it may promote hypertensive renal injury.

Salt, inflammation, IL-17 and hypertension

Traditionally, arterial hypertension and subsequent end-organ damage have been attributed to haemodynamic 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 microorganisms 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. Over the past few years, important findings have revolutionized hypertension research. Firstly, in 2007, a seminal paper showed that adaptive immunity is involved in the pathogenesis of hypertension. Secondly, salt storage in the skin and its consequences for cardiovascular physiology were discovered. Thirdly, after the discovery that salt promotes the differentiation of CD4⁺ T cells into T_H 17 cells, it was demonstrated that salt directly changes several cells of the innate and adaptive immune system and aggravates autoimmune disease but may improve antimicrobial defence. Herein, we will review pathways of activation of immune cells by salt in hypertension as the framework for understanding the multiple roles of salt and immunity in arterial hypertension and autoimmune disease. LINKED ARTICLES: This article is part of a themed section on Immune Targets in Hypertension. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.12/issuetoc.

Autoimmune Renal Disease Is Exacerbated by S1P-Receptor-1-Dependent Intestinal Th17 Cell Migration to the Kidney

Th17 cells are most abundant in the gut, where their presence depends on the intestinal microbiota. Here, we examined whether intestinal Th17 cells contribute to extra-intestinal Th17 responses in autoimmune kidney disease. We found high frequencies of Th17 cells in the kidneys of patients with antineutrophil cytoplasmatic antibody (ANCA)-associated glomerulonephritis. We utilized photoconversion of intestinal cells in Kaede mice to track intestinal T cell mobilization upon glomerulonephritis induction, and we found that Th17 cells egress from the gut in a S1P-receptor-1-dependent fashion and subsequently migrate to the kidney via the CCL20/CCR6 axis. Depletion of intestinal Th17 cells in germ-free and antibiotic-treated mice ameliorated renal disease, whereas expansion of these cells upon Citrobacter rodentium infection exacerbated pathology. Thus, in some autoimmune settings, intestinal Th17 cells migrate into target organs, where they contribute to pathology. Targeting the intestinal Th17 cell "reservoir" may present a therapeutic strategy for these autoimmune disorders.

A pathogenic role of complement in arterial hypertension and hypertensive end organ damage

The self-amplifying cascade of messenger and effector molecules of the complement system serves as a powerful danger-sensing system that protects the host from a hostile microbial environment, while maintaining proper tissue and organ function through effective clearance of altered or dying cells. As an important effector arm of innate immunity, it also plays important roles in the regulation of adaptive immunity. Innate and adaptive immune responses have been identified as crucial players in the pathogenesis of arterial hypertension and hypertensive end organ damage. In line with this view, complement activation may drive the pathology of hypertension and hypertensive injury through its impact on innate and adaptive immune responses. It is well known that complement activation can cause tissue inflammation and injury and complement-inhibitory drugs are effective treatments for several inflammatory diseases. In addition to these proinflammatory properties, complement cleavage fragments of C3 and C5 can exert anti-inflammatory effects that dampen the inflammatory response to injury. Recent experimental data strongly support a role for complement in arterial hypertension. The remarkably similar clinical and histopathological features of malignant nephrosclerosis and atypical hemolytic uremic syndrome, which is driven by complement activation, suggest a role for complement also in the development of malignant nephrosclerosis. Herein, we will review canonical and noncanonical pathways of complement activation as the framework to understand the multiple roles of complement in arterial hypertension and hypertensive end organ damage.

The complement receptor C5aR1 contributes to renal damage but protects the heart in angiotensin II-induced hypertension

Adaptive and innate immune responses contribute to hypertension and hypertensive end-organ damage. Here, we determined the role of anaphylatoxin C5a, a major inflammatory effector of the innate immune system that is generated in response to complement activation, in hypertensive end-organ damage. For this purpose, we assessed the phenotype of C5a receptor 1 (C5aR1)-deficient mice in ANG II-induced renal and cardiac injury. Expression of C5aR1 on infiltrating and resident renal as well as cardiac cells was determined using a green fluorescent protein (GFP)-C5aR1 reporter knockin mouse. Flow cytometric analysis of leukocytes isolated from the kidney of GFP-C5aR1 reporter mice showed that 28% of CD45-positive cells expressed C5aR1. Dendritic cells were identified as the major C5aR1-expressing population (88.5%) followed by macrophages and neutrophils. Using confocal microscopy, we detected C5aR1 in the kidney mainly on infiltrating cells. In the heart, only infiltrating cells stained C5aR1 positive. To evaluate the role of C5aR1 deficiency in hypertensive injury, an aggravated model of hypertension was used. Unilateral nephrectomy was performed followed by infusion of ANG II (1.5 ng·g(-1)·min(-1)) and salt in wild-type (n = 34) and C5aR1-deficient mice (n = 32). C5aR1-deficient mice exhibited less renal injury, as evidenced by significantly reduced albuminuria. In contrast, cardiac injury was accelerated with significantly increased cardiac fibrosis and heart weight in C5aR1-deficient mice after ANG II infusion. No effect was found on blood pressure. In summary, the C5a:C5aR1 axis drives end-organ damage in the kidney but protects from the development of cardiac fibrosis and hypertrophy in experimental ANG II-induced hypertension.

Deficiency of the interleukin 17/23 axis accelerates renal injury in mice with deoxycorticosterone acetate+angiotensin ii-induced hypertension

T cells participate in angiotensin II (Ang II)-induced hypertension. However, the specific subsets of T cells that are important in the end-organ damage are unknown. T-helper 17 cells are a recently identified subset that produces interleukin 17 (IL-17) and requires interleukin 23 (IL-23) for expansion. To evaluate the role of the T-helper 17 immune response in hypertensive renal and cardiac end-organ damage, hypertension was induced with deoxycorticosterone acetate (DOCA)+Ang II in wild-type (n=39) and IL-17-deficient (n=31) mice. The injury was evaluated at day 4 and day 14. To inactivate the IL-17/IL-23 axis at a different point, DOCA+Ang II hypertension was also induced in IL-23p19-deficient mice. Renal infiltration by T-helper 17 cells was increased in hypertensive wild-type mice. Systolic blood pressure did not differ between hypertensive IL-17-deficient and wild-type mice. Three days after induction of hypertension, a significantly higher albuminuria was found in IL-17-deficient than in wild-type mice (196±64 versus 58±16 mg/mg albumin/creatinine). Histology revealed significantly more glomerular injury (1.04±0.06 versus 0.67±0.05) and renal infiltration of γδ T cells in IL-17-deficient than in wild-type mice after 14 days. Similarly, significantly higher albuminuria, glomerular injury, and γδ T cell infiltration were found in IL-23p19-deficient mice with DOCA+Ang II-induced hypertension. DOCA+Ang II also induced cardiac damage as assessed by heart weight, cardiac fibrosis, as well as expression of fetal genes and matrix components, but no significant differences were found among IL-17(-/-), IL-23p19(-/-), and wild-type mice. IL-17/IL-23 deficiency accelerates DOCA+Ang II-induced albuminuria and hypertensive renal but not cardiac end-organ damage.

CCR5 deficiency does not reduce hypertensive end-organ damage in mice

BACKGROUND

CCR5 is expressed on infiltrating T cells in hypertensive mice and CCR5 antagonists reduce hypertension making CCR5 an interesting target in treatment of hypertension.

METHODS

To evaluate the role of CCR5 in hypertensive renal and cardiac end-organ damage, we induced hypertension with desoxycorticosterone acetate (DOCA) and angiotensin II (Ang II) in wild-type (WT) and CCR5-deficient mice.

RESULTS

CCR5 expression was increased in renal cortex and cardiac tissue as measured by quantitative PCR. Systolic blood pressure and renal function did not differ between hypertensive CCR5(-/-) and WT mice. DOCA + Ang II induced massive albuminuria and glomerular injury but no difference was found between CCR5(-/-) and WT mice. In addition, no difference was found for renal inflammation as measured by infiltrating T cells, macrophages, and CCL2 expression. The renal expression of the CCR5 ligands, CCL3, and CCL5 was increased in the kidney of hypertensive mice. For CCL3 the increase was significantly higher in CCR5(-/-) than in WT mice. DOCA + Ang II induced cardiac damage as assessed by heart weight, cardiac fibrosis as well as expression of fetal and matrix components but no significant difference was found between CCR5(-/-) and WT mice.

CONCLUSIONS

CCR5 deficiency does not influence hypertensive renal and cardiac end-organ damage. Cells that infiltrate by expression of CCR5 are either not pathogenic or CCR5-positive leukocytes can migrate via alternative chemokine receptors. Beneficial effects of CCR5 antagonists in hypertension are most likely due to unspecific effects of the antagonists. Possibly, other chemokine receptors in concert with CCR5 are important for hypertensive injury.

Rho kinase inhibition attenuates LPS-induced renal failure in mice in part by attenuation of NF-kappaB p65 signaling

Rho kinase signaling regulates inflammatory cell migration and chemokine production. We therefore investigated the mechanisms of Rho-kinase-dependent inflammation in lipopolysaccharide (LPS)-induced renal failure. C57/BL6 mice received intraperitoneal LPS with or without daily treatment with specific Rho kinase inhibitors (Y-27632 or HA-1077; 5 mg/kg). Rho kinase inhibitors were applied in a preventive (12 or 1 h before LPS) or a therapeutic (6 h after LPS) scheme. Both protected renal function and decreased tubular injury in LPS-treated mice. Enhanced Rho kinase activity was inhibited by HA-1077 in capillary endothelial cells, inflammatory cells, and tubuli by analysis of Rho kinase substrate phosphorylation. Early neutrophil influx was reduced by HA-1077 without reduction of the proinflammatory cytokine TNFalpha. In contrast, HA-1077 decreased the influx of monocytes/macrophages coinciding with reduced expression of the NF-kappaB-regulated chemokines CCL5 and CCL2. We therefore examined NF-kappaB signal transduction and found that NF-kappaB p65 phosphorylation and nuclear translocation were reduced by Rho kinase inhibition. IkappaBalpha degradation was not altered during the first 6 h but was reduced by HA-1077 at later time points. NF-kappaB p50-deficient mice were similarly protected from renal injury by Rho kinase inhibition further supporting the prominent role for p65 in Rho kinase inhibition. Together, these data suggest that Rho kinase inhibition by preventive or therapeutic treatment effectively reduced endotoxic kidney injury in part by attenuation of NF-kappaB p65 activation.

A pitfall of glomerular sieving: profibrotic and matrix proteins derive from the Bowman's capsule and not the glomerular tuft in rats with renovascular hypertension

BACKGROUND

The glomeruli in the non-clipped kidney of rats with 2-kidney, 1-clip hypertension are a classical model for studying the mechanisms of glomerular injury.

METHODS

In the present study, we compared the glomerular expression of PAI-1 and collagen I alpha1 mRNA from glomeruli isolated by the classic technique of sieving with the recently developed technique of tissue laser microdissection. For quantification of mRNA from both methods, real-time PCR was used.

RESULTS

Real-time PCR revealed a 9.0 +/- 1.3- and a 7.1 +/- 0.2-fold induction of PAI-1 and collagen I alpha 1, respectively, in the glomeruli from hypertensive rats isolated by sieving. However, in situ hybridization and microdissection revealed that expression of both mRNAs was mainly from the Bowman's capsule and not from the glomerular tuft (10.7 +/- 1.3- and 7.2 +/- 0.6-fold higher induction in whole glomeruli compared with tuft alone).

CONCLUSION

This emphasizes that studies focusing on processes in the mesangium, endothelial cells or podocytes should not rely on glomeruli obtained by sieving. Rather, a technique like the laser microdissection or in situ hybridization should be applied which allows the clear separation of different glomerular and periglomerular compartments.

Treatment of arterial hypertension in obese patients

The prevalence of obesity is steadily increasing. Hypertension is one of the most common co-morbidities of obesity and significantly contributes to morbidity and mortality. Most obese hypertensive patients require antihypertensive drug treatment. However, current guidelines do not give specific recommendations for antihypertensive therapy of obese hypertensive patient. Some antihypertensive agents may have unwanted effects on the metabolic and hemodynamic abnormalities that link obesity and hypertension. Due to the lack of guidelines, this chapter provides recommendations for or against each class of antihypertensive agents mostly based on subjective criteria and pathophysiologic assumptions. Diuretics and betablockers are reported to reduce insulin sensitivity and increase lipid levels, whereas calcium antagonists are metabolically neutral and ACE-inhibitors as well as angiotensin receptor blockers increase insulin sensitivity. Sodium retention plays a central role in the development of obesity-related hypertension. Therefore, treatment with an ACE-inhibitors or a diuretic should be considered as first-line antihypertensive drug therapy in obesity-hypertension.

Statin therapy in patients with chronic kidney disease: to use or not to use

Dyslipdemia is a common complication of chronic kidney disease (CKD) and contributes to high cardiovascular morbidity and mortality of CKD patients. Experimental studies have demonstrated that lipids induce glomerular and tubulointerstitial injury and that lipid-lowering treatments ameliorate renal injury. Therapy with statins not only has the potential to lower cardiovascular morbidity and mortality in patients with CKD but also to slow progression of renal disease. Whereas the guidelines for treatment of hyperlipidaemia in nonrenal patients are based on prospective, randomized, placebo-controlled mega-trials, such data are not available for CKD patients. This review outlines the limited information currently available on the effect of statins among patients with CKD and summarizes the ongoing randomized trials designed to address this question.

Angiotensin II upregulates toll-like receptor 4 on mesangial cells

Angiotensin II (AngII) mediates proinflammatory properties by activating NF-kappaB transcription factor nuclear translocation and inducing the expression of chemokines. For examination of whether AngII modulates the expression of Toll-like receptor 4 (TLR4), a key element of the innate immune system that senses LPS, mouse mesangial cells (MMC) were treated with AngII. AngII upregulated TLR4 mRNA and protein in MMC, and this effect was mediated through AngII type 1 receptors. Reporter gene experiments indicate that an activating protein-1 (AP-1) as well as an E-26 specific sequence (Ets) binding site in the TLR4 promoter are responsible for the AngII-stimulated transcriptional activity of the TLR4 gene. Preincubation of MMC with AngII enhanced LPS-induced NF-kappaB activation and chemokine expression. Immunohistochemical analyses revealed that double-transgenic rats that overexpressed human renin and angiotensinogen expressed higher levels of glomerular TLR4 compared with normal Sprague-Dawley rats. In vivo, infusion with AngII but not with norepinephrine into rats for 7 d also enhanced glomerular NF-kappaB activation after systemic application of LPS, suggesting that the effects are independent of concomitantly induced hypertension. Together, these observations suggest that AngII leads to an activation of the innate immune system by a novel mechanism involving the upregulation of TLR4. Our data contribute to a better understanding of how exogenous infections may trigger renal autoimmune processes, particularly in pathophysiologic situations with high renal AngII concentrations. Because TLR4 binds endogenous ligands (e.g., extracellular matrix components) in addition to microbial products, AngII-mediated upregulation of TLR4 also could be relevant for the development of inflammation in many noninfectious renal diseases.

Angiotensin II and Cell Cycle Regulation

Angiotensin II has emerged as an important growth factor for vascular, cardiac, and renal cells. Depending on the specific cell type and presence of other growth factors, angiotensin II induces proliferation (replication of DNA with subsequent successful division of cells), hypertrophy (increase in cell size, cell protein, and mRNA content without DNA replication), apoptosis (programmed cell death), or differentiation. Such angiotensin II-mediated modulation of growth process may underlie various pathophysiological processes such as atherosclerosis, vascular and cardiac remodeling, and progression of chronic renal disease. Clearly, angiotensin II-induced proliferation requires complete cell progression through the various steps of the cell cycle. In contrast, cells undergoing angiotensin II-mediated hypertrophy are arrested in the G1-phase. Upregulation of cell cycle-dependent kinase inhibitors (eg, p27Kip1) plays an important role in this process. Although accumulating evidence suggests that apoptosis is cell cycle-dependent, only few data are currently available concerning the interaction of angiotensin II with the cell cycle machinery in apoptosis. We review the various angiotensin II-mediated growth processes and their relationship to events governing cell cycle regulation.

Beneficial and adverse renal and vascular effects of the vasopeptidase inhibitor omapatrilat in renovascular hypertensive rats

BACKGROUND

Vasopeptidase inhibitors are a new class of compounds that inhibit both angiotensin-converting enzyme (ACE) and neutral endopeptidase. This study determined whether treatment with the vasopeptidase inhibitor omapatrilat (OMA) produced different effects on renal and cardiovascular structure compared with inhibition of ACE by enalapril (ENP) in rats with two-kidney, one clip hypertension (2K1C).

METHODS

Hypertensive 2K1C rats were randomized into four groups and studied for another 8 weeks: no treatment, OMA, ENP or ENP combined with the diuretic hydrochlorothiazide (ENP + HCTZ). Albuminuria, vascular and renal histology as well as glomerular expression of transforming growth factor-beta (TGF-beta) were determined at the end of the experiment.

RESULTS

OMA decreased blood pressure slightly better than ENP. However, combination of ENP with a diuretic lowered blood pressure equally effective as OMA. OMA was numerically more efficient in reducing cardiovascular and renal hypertensive changes compared with ENP. In contrast, the combination of ENP + HCTZ was as efficient as OMA. However, OMA lowered overexpression of TGF-beta in the non-clipped kidney better than ENP or ENP +HCTZ. Antihypertensive therapy surprisingly decreased renal function as shown by increased plasma creatinine and urea and decreased creatinine clearance.

CONCLUSION

OMA is marginally more potent compared with ENP alone in lowering blood pressure and preventing cardiovascular and renal injury. This effect may be due to slightly better blood pressure reduction because addition of HCTZ enhances the cardio- and nephroprotective capacity of ENP. In contrast, OMA reduces TGF-beta overexpression in the non-clipped kidney better than ENP or ENP + HCTZ. Therefore, vasopeptidase inhibition is not superior to ACE inhibition in the prevention of cardiovascular and renal damage Goldblatt hypertension.

The renin-angiotensin system and progression of renal disease: from hemodynamics to cell biology

The renal community is faced with an ever increasing number of patients reaching end-stage renal failure. Clinical studies have provided clear evidence that angiotensin-converting enzyme (ACE) inhibitors, and probably also AT1 receptor antagonists, at least in patients suffering from type 2 diabetes, slow disease progression to end-stage renal failure. This protective effect of drugs interfering with the renin-angiotensin system (RAS) are in part independent of reduction in systemic blood pressure, but involve normalization of glomerular hyperperfusion and hyperfiltration, restoration of altered glomerular barrier function, and reduction of stimulated tubular fluid reabsorption. Angiotensin II (ANG II) has emerged in the last decade as a multifunctional cytokine exhibiting many non-hemodynamic properties such as acting as a growth factor and profibrogenic cytokine, and even having proinflammatory properties. This review tries to bridge the classical hemodynamic actions of ANG II in the kidney with the more recently characterized effects of this vasopeptide. Finally, clinical implications are suggested based on data from clinical studies. A thorough understanding of the RAS is important to recognize the potential of nephroprotective strategies through inhibition of its components.

Chronic anti-Thy-1 nephritis is aggravated in the nonclipped but not in the clipped kidney of Goldblatt hypertensive rats

BACKGROUND

We have previously shown that renovascular hypertension does not inhibit healing of the acute Thy-1 nephritis. To test whether a chronic model of the Thy-1 nephritis is more susceptible to high blood pressure, the repetitive hit model was evaluated in rats with 2-kidney, 1-clip Goldblatt hypertension.

METHODS

Six weeks after initiation of 2-kidney, 1-clip hypertension, chronic Thy-1 glomerulonephritis was induced in hypertensive rats by four consecutive injections of rabbit antiserum in weekly intervals. Renal structure and function were examined two weeks after the last injection. Glomerular binding of rabbit IgG as well as expression of transforming growth factor-beta (TGF-beta), alpha-smooth muscle actin (alpha-SMA) and cyclooxygenase (COX)-1 and -2 were evaluated by Western blotting.

RESULTS

Similar glomerular deposition of rabbit IgG was detected in normotensive rats and in both kidneys of Goldblatt hypertensive rats indicating similar delivery and binding of the heterologous antibody. Induction of the repetitive Thy-1 model significantly enhanced glomerular damage in the nonclipped kidney and increased albuminuria. Surprisingly, no glomerular damage developed in the clipped kidney of nephritic hypertensive rats. In contrast, increased glomerular volume and increased expression of TGF-beta, alpha-SMA as well as COX-1 and COX-2 were found in normotensive nephritic rats and in both kidneys of nephritic hypertensive rats.

CONCLUSION

Glomerular and tubulointerstitial damage of the chronic Thy-1 model is dramatically enhanced in the nonclipped kidneys of Goldblatt hypertensive rats. In contrast, the clipped kidney is completely protected from this immunological injury despite similar activation of glomerular cells, induction of TGF-beta, COX-1 and COX-2 and glomerular hypertrophy.

Angiotensin II infusion ameliorates the early phase of a mesangioproliferative glomerulonephritis

BACKGROUND

Inhibition of the renin-angiotensin system slows the progression of chronic renal disease.

METHODS

To test whether angiotensin II (Ang II) infusion aggravates or ameliorates an acute glomerulonephritis, the peptide was infused (200 ng/min by osmotic minipump) in rats with an anti-thymocyte antibody-induced glomerulonephritis (ATS).

RESULTS

Ang II significantly increased blood pressure. Following injection of the antibody, similar glomerular binding of rabbit IgG and rat complement C3 was detected in ATS and Ang II+ATS rats, indicating no differences in delivery and binding of the antibody. Ang II infusion, however, induced a significant reduction in glomerular monocyte infiltration, cell proliferation and matrix expansion in nephritic rats compared to rats with nephritis without Ang II. The antiproliferative effect of Ang II was inhibited by the Ang II type 1 (AT1) receptor blocker irbesartan, but not by the AT2 receptor blocker PD 123319, indicating that this effect was likely transduced by AT1 receptors. Norepinephrine infusion (600 ng/min) produced a similar degree of hypertension, but did not affect glomerular proliferation in nephritic rats. Ang II induced the glomerular expression of the cell cycle inhibitor p27KIP1 and of transforming growth factor-beta (TGF-beta) and inhibited expression of monocyte chemotactic protein 1 (MCP-1).

CONCLUSION

Ang II surprisingly ameliorates glomerular monocyte infiltration, proliferation and matrix expansion in ATS nephritis. Ang II-mediated induction of cyclin kinase inhibitors and TGF-beta may contribute to the protection of the glomerulus from inflammatory injury by inducing cell cycle arrest and attenuating activation of local and recruited cells. Alternatively, Ang II might protect the kidney at least in part by less inflow of disease activators due to reduction of renal blood flow. Therefore, activation of the renin-angiotensin system may have protective effects in certain pathophysiological situations.

Agonist-specific regulation of monocyte chemoattractant protein-1 expression by cyclooxygenase metabolites in hepatic stellate cells

Activated hepatic stellate cells (HSC) regulate the liver "wound-healing" response through expression of chemokines, including monocyte chemoattractant protein-1 (MCP-1), which participate in the formation of the inflammatory infiltrate during liver injury. Cyclooxygenase (COX) catalyzes the conversion of arachidonic acid into prostaglandins, which may contribute to the inflammatory response. In this study, we investigated the effects of COX inhibitors on the expression of MCP-1 in cultured HSC. Pretreatment of HSC with nonspecific COX inhibitors such as indomethacin or ibuprofen markedly reduced the expression of MCP-1 caused by exposure to tumor necrosis factor alpha (TNF-alpha) or interleukin-1alpha (IL-1alpha). NS-398, a specific COX-2 inhibitor, also resulted in a dose-dependent inhibition of MCP-1 gene and protein expression. These effects were dependent on reduced MCP-1 transcription, as established using a reporter plasmid. In contrast, the up-regulation of MCP-1 expression caused by interferon gamma (IFN-gamma) was not sensitive to COX inhibitors. Quiescent HSC did not show detectable expression of COX-2, which became evident after activation in culture, and while TNF-alpha and IL-1alpha markedly increased the expression of COX-2, IFN-gamma did not have any effects. Pretreatment of HSC with the stable cyclic adenosine monophosphate (cAMP) analog, 8-bromo cAMP, reverted the effects of the COX-2 inhibitor, but not of a nuclear factor-kappaB (NF-kappaB) inhibitor, demonstrating that prostaglandins modulate MCP-1 expression via production of cAMP. On the other hand, the action of NF-kappaB inhibitors was negligible in IFN-gamma-stimulated cells. These findings indicate that cross-talk between cytokines and a prostaglandin-cAMP pathway differentially regulates the proinflammatory potential of HSC, contributing to the modulation of liver tissue inflammation.

Renovascular hypertension does not influence repair of glomerular lesions induced by anti-thymocyte glomerulonephritis

BACKGROUND

Systemic hypertension is a risk factor for progression of renal disease. However, it is not clear whether hypertension has an effect on healing or regression of immune-mediated glomerular damage. To evaluate this effect, we applied a model of glomerulonephritis in rats with two-kidney, one-clip hypertension and studied the effect of hypertension on the healing process of this nephritis.

METHODS

The anti-thymocyte serum (ATS) glomerulonephritis was induced in rats six weeks after initiation of two-kidney, one-clip hypertension, when blood pressure was already increased. Renal structure and function were examined six weeks later. Glomerular expression of alpha smooth muscle actin, the cell cycle inhibitor p27Kip1, and transforming growth factor-beta (TGF-beta) was evaluated by Western blotting. Glomerular proliferation, monocyte infiltration, and fibronectin were examined by immunohistochemistry.

RESULTS

Decreased survival, an increase of proteinuria, as well as increased glomerular and tubulointerstitial damage, were found in hypertensive rats compared with normotensive rats. Expression of fibronectin, alpha-smooth muscle actin, TGF-beta, and p27Kip1 was increased in the nonclipped kidney. Complete healing of the glomerular changes associated with the nephritis occurred in normotensive nephritic rats. Surprisingly, complete healing of the nephritis was also found in the clipped as well as nonclipped kidneys of renovascular hypertensive rats. No significant differences could be found for survival, proteinuria, glomerular size, proliferation, monocyte/macrophage infiltration, sclerosis, tubulointerstitial damage, as well as expression of alpha-smooth muscle actin, TGF-beta, fibronectin, and p27Kip1 between hypertensive rats with and without nephritis.

CONCLUSION

These data demonstrate that renovascular hypertension does not influence healing of the glomerular lesions in the anti-thymocyte serum nephritis. This is a rather surprising observation and leaves the question open of which role, in fact, blood pressure may have on the reparative phase of an acute glomerulonephritis, or whether its role depends on the type of glomerulonephritis.

Effect of renovascular hypertension on experimental glomerulonephritis in rats

Systemic hypertension is a major risk factor that determines the rate of progression of kidney disease. The underlying mechanisms, however, are incompletely understood. To gain insight into these mechanisms, the present study was undertaken to characterize the effects of renovascular hypertension on the course of anti-thymocyte antibody-induced glomerulonephritis. Glomerulonephritis was induced in rats 6 weeks after the initiation of two-kidney, one-clip hypertension, when blood pressure was already increased. Structure and function of the clipped and the nonclipped kidney were examined 5 days later. Glomerular filtration rate (GFR) was measured by inulin clearance. The induction of nephritis did not alter the blood pressure in either hypertensive rats or normotensive controls. Albuminuria increased slightly in normotensive rats after the induction of nephritis, whereas no significant differences were found between hypertensive rats with or without nephritis. No significant differences were found for the GFR values of normotensive controls and nephritic animals or for values in the clipped kidney with or without nephritis. However, the GFR of the nonclipped kidney was significantly reduced in nephritic animals as compared with all other groups. Morphologic evaluation revealed that hypertensive rats with nephritis exhibited a combination of characteristics of nephritis and hypertensive glomerular injury. Histologic findings of nephritis, such as glomerular binding of rabbit IgG and glomerular proliferation and mesangial matrix expansion, were similar after the induction of nephritis in controls and in the clipped and nonclipped kidneys of hypertensive animals. However, intraglomerular microaneurysms were significantly more often found in the non-clipped kidneys after the induction of nephritis. Hypertension-induced deterioration of glomerular function was not associated with marked morphologic deterioration but rather with a combination of the characteristics of nephritis and hypertensive glomerular injury.

Expression of monocyte chemotactic protein-1 precedes monocyte recruitment in a rat model of acute liver injury, and is modulated by vitamin E

BACKGROUND

Increased expression of monocyte chemotactic protein-1 (MCP-1) has been indicated as a mechanism underlying leukocyte recruitment after liver injury. In this study we examined the temporal relationship between MCP-1 expression and the appearance of monocyte infiltration during acute liver injury. In addition, we tested the effects of vitamin E, a well known antioxidant, on these parameters. Rats were intoxicated with a single intragastric administration of CCl4 with or without pretreatment with vitamin E (atocopherol).

METHODS

Monocyte chemotactic protein-1 expression was analyzed by northern blotting and in situ hybridization and monocyte infiltration was determined by ED-1 immunostaining. The results were quantitated by computerized image analysis. Expression of MCP-1 mRNA was significantly increased as early as 12 hours following injury, and progressively increased thereafter. In contrast, a significant increase in the number of ED-1 positive cells, an index of monocyte infiltration, was observed only 24 and 48 hours after injury.

RESULTS

Vitamin E markedly reduced MCP-1 expression at the mRNA and protein levels, and caused a significant reduction in the number of monocyte/macrophages, indicating a role for oxidative stress in the induction of MCP-1 expression in vivo. Accordingly, in cultured hepatic stellate cells, different oxidative stress-related molecules increased MCP-1 mRNA.

CONCLUSIONS

These data suggest the existence of a direct relationship between MCP-1 expression and monocyte infiltration after acute liver injury, and that preventing the generation of oxidative stress-related molecules results in decreased expression and release of this chemokine.

Chemokines, renal disease, and HIV infection

Renal disease is characterized by the influx of leukocytes into the injured tissue. Before leukocytes can exert their effects on renal damage or repair, they have to reach the site of injury. To recruit specific populations of leukocytes during inflammation is the role of a family of cytokines called chemokines. The characterization of this family has emerged within the past years, yet chemokines have already been the subject of thousands of scientific reports and promise to have many clinical applications. There is good evidence that chemokines contribute to leukocyte infiltration in glomeruli and interstitium and that they play a pivotal role in various renal diseases. The fact that there exist so many chemokines suggests the biological need for redundancy to effect recruitment of immune cells. Although they were originally defined as host defense proteins, chemokines clearly have other functions that extend well beyond the regulation of leukocyte migration. The recent suggestion that chemokines may contribute to a slow progression of the human immunodeficiency virus (HIV) infection and the very recent identification of chemokine receptors as docking molecules for HIV infection add another aspect to chemokine research. The speed at which researchers are exploring the HIV-chemokine connection is evident in the large number of publications on this topic as well as the rapid translation of publications into possible therapeutic applications. Delineating a precise role for chemokines in mediating pathologic changes is an area of fruitful investigation.

A Complex Element Regulates IFN-γ-Stimulated Monocyte Chemoattractant Protein-1 Gene Transcription

Monocyte chemoattractant protein-1 (MCP-1) is induced in chronic osseous inflammation, and is temporally and spatially correlated with monocyte recruitment. We investigated the mechanism of MCP-1 regulation in a human osteoblastic cell line in response to IFN-γ, a potent mediator of the immune inflammatory response. Nuclear run-on and stability studies demonstrated that IFN-γ stimulated MCP-1 transcription and did not enhance mRNA stabilization. Using MCP-1 promoter/reporter gene constructs, we determined that IFN-γ-enhanced MCP-1 transcription is regulated by a 29-bp element located at −227 relative to the ATG start codon. This element contains a 13-bp CT-rich sequence (GCTTCCCTTTCCT) adjacent to a IFN-γ activation site (GAS). Since deletion of the CT sequence enhanced both the magnitude and duration of IFN-γ-stimulated, GAS-mediated transcription, we have termed it the IFN response-inhibitory sequence (IRIS). The combined IRIS/GAS sequence is highly conserved in mouse, rat, and bovine MCP-1 genes. In gel-shift assays, nuclear extracts from IFN-γ-stimulated osteoblastic cells formed two specific inducible bands with labeled IRIS/GAS DNA. Both bands were supershifted by anti-STAT1 Abs, but not by Abs to STAT2, p48(ISGF-3γ), IFN-regulatory factor-1, or IFN-regulatory factor-2. Formation of one of the bands required the presence of the IRIS moiety. IRIS/GAS DNA also formed a number of specific complexes with constitutively expressed factors, none of which were affected by the above Abs. These studies establish a mechanism for IFN-γ-stimulated MCP-1 expression and identify a complex element that regulates MCP-1 gene transcription.

A complex element regulates IFN-gamma-stimulated monocyte chemoattractant protein-1 gene transcription

Monocyte chemoattractant protein-1 (MCP-1) is induced in chronic osseous inflammation, and is temporally and spatially correlated with monocyte recruitment. We investigated the mechanism of MCP-1 regulation in a human osteoblastic cell line in response to IFN-gamma, a potent mediator of the immune inflammatory response. Nuclear run-on and stability studies demonstrated that IFN-gamma stimulated MCP-1 transcription and did not enhance mRNA stabilization. Using MCP-1 promoter/reporter gene constructs, we determined that IFN-gamma-enhanced MCP-1 transcription is regulated by a 29-bp element located at -227 relative to the ATG start codon. This element contains a 13-bp CT-rich sequence (GCTTCCCTTTCCT) adjacent to a IFN-gamma activation site (GAS). Since deletion of the CT sequence enhanced both the magnitude and duration of IFN-gamma-stimulated, GAS-mediated transcription, we have termed it the IFN response-inhibitory sequence (IRIS). The combined IRIS/GAS sequence is highly conserved in mouse, rat, and bovine MCP-1 genes. In gel-shift assays, nuclear extracts from IFN-gamma-stimulated osteoblastic cells formed two specific inducible bands with labeled IRIS/GAS DNA. Both bands were supershifted by anti-STAT1 Abs, but not by Abs to STAT2, p48(ISGF-3y), IFN-regulatory factor-1, or IFN-regulatory factor-2. Formation of one of the bands required the presence of the IRIS moiety. IRIS/GAS DNA also formed a number of specific complexes with constitutively expressed factors, none of which were affected by the above Abs. These studies establish a mechanism for IFN-gamma-stimulated MCP-1 expression and identify a complex element that regulates MCP-1 gene transcription.

[Diagnostic and therapeutic procedures by doctors for patients in a hypertensive crisis. An inquiry in 56 internal medicine clinics]

BACKGROUND AND OBJECTIVE

Despite official guidelines on the diagnosis and treatment of hypertensive crisis, the extent to which they are being followed in routine medical practice is unknown. This study was undertaken to discover how hospital doctors were handling cases of hypertensive crisis (HC).

MATERIALS AND METHODS

Physicians were requested to participate in a multiple-choice questionnaire study, relating to the diagnosis of HC, any emergency diagnosis and choice of antihypertensive drugs, these questionnaires to be distributed among the medical staff. Ultimately 463 questionnaires (one per doctor) were sent out and 325 were completed (response rate of 70%).

RESULTS

The most frequently mentioned blood pressure values characteristics for HC were > 200 systolic and > 120 diastolic. 160/90 was given most often as the therapeutic goal, which most doctors wanted to reach in an HC within 30 to 60 min. The calcium-antagonist nifedipine was the drug of first choice for almost all clinical presentations. Second was intravenously urapidil, an alpha-agonist. Nitroglycerin was named as first choice only for pulmonary oedema or myocardial infarction. In everyone of the stated conditions most doctors were eager to avoid using beta-blockers. As for the drug of first choice in associated myocardial infarction, 111 doctors named nifedipine, 28 wanted to avoid it and 45 considered it contraindicated.

CONCLUSION

These data show a marked discrepancy between recommended guidelines and actual practice in the management of hypertensive crisis.

Chemokines and renal disease

Chemokines are low molecular weight inflammatory cytokines with chemoattractant properties as their major biologic effect. They are classified into at least two families. C-X-C chemokines (alpha subfamily) act primarily on neutrophils, while C-C chemokines act preferentially on monocytes. Chemokine receptors are G protein-coupled receptors that form a family of structurally and functionally related proteins. Chemokines are induced in cells and tissue in response to proinflammatory cytokines. They are produced by glomerular, tubular interstitial, and blood vessel cells. There is good evidence that chemokines contribute to neutrophil and mononuclear cell infiltration in glomeruli and interstitium. Their expression is increased in renal disease, and neutralization studies using antibodies in vivo demonstrated a role for certain chemokines in mediating renal pathology and proteinuria. Interleukin-8, RANTES, and monocyte chemotactic peptide are the best-studied chemokines in the kidney. Development of specific antibodies and receptor antagonists should help establish the precise role of these mediators in renal disease. Important therapeutic implications may result from this work.

PKC alpha regulates thrombin-induced PDGF-B chain gene expression in mesangial cells

Thrombin is a potent mitogen for mesangial cells and stimulates PDGF B-chain gene expression in these cells. It also activates phospholipase C (PLC) resulting in an increase in cytosolic Ca2+ and diacylglycerol (DAG) that are the physiological activators of protein kinase C (PKC). Immunoprecipitation of specific PKC isotypes from thrombin-stimulated mesangial cells with subsequent measurement of their enzymatic activity shows activation of Ca(2+)-dependent PKC alpha and Ca(2+)-independent PKC zeta in a time dependent manner. Optimum activation of both of these isozymes was obtained at 60 minutes. PKC alpha activity increased 83% over basal while activity of PKC zeta increased 104%. Prolonged exposure of mesangial cells to phorbol myristate acetic acid (PMA) inhibited the enzymatic activity of PKC alpha but not PKC zeta. This inhibition of PKC alpha had no effect on thrombin-induced DNA synthesis but abolished PDGF B-chain gene expression induced by thrombin. These data provide the first evidence that PKC alpha activation is necessary for thrombin-induced PDGF B-chain gene expression but not for thrombin-induced DNA synthesis.

Thrombin regulates expression of monocyte chemoattractant protein-1 in vascular smooth muscle cells

Thrombin, a serine protease generated at sites of vascular injury, plays a role in the pathogenesis of atherosclerosis and restenosis after angioplasty. Adherence of monocytes to the endothelium and migration into the subendothelial space is an important early event in the pathogenesis of atherosclerosis. Monocyte chemoattractant protein 1 (MCP-1) may be an important mediator of monocyte recruitment to the tissue in this and other diseases. We have characterized the expression of MCP-1 in vascular smooth muscle cells (VSMCs) isolated from human renal artery and studied its regulation by thrombin. Serum-deprived cells release monocyte chemotactic activity that is neutralized (80%) by an MCP-1 antibody. The antibody recognized a 13- and 15-kD protein in smooth muscle cell-conditioned medium. Thrombin stimulates MCP-1 gene expression in a concentration- and time-dependent manner. An increase over basal levels was observed with concentrations of thrombin as low as 0.05 U/mL. The maximal effect occurred at 5 U/mL. The stimulatory effect was detected within 1 hour, reached a maximum at 3 hours, and was still present at 8 to 24 hours after the addition of thrombin. A concentration- and time-dependent effect of thrombin on MCP-1 gene expression was also found in rat VSMCs. The thrombin protease inhibitor hirudin blocked thrombin-induced MCP-1 expression. Thrombin stimulated the release of MCP-1 protein in conditioned medium of human VSMCs as measured by radioimmunoassay and chemotactic assay. Thrombin also increased monocyte chemotactic activity in short-term organ cultures of rat aortic rings and in first passage cells.(ABSTRACT TRUNCATED AT 250 WORDS)

A nuclear protein in mesangial cells that binds to the promoter region of the platelet-derived growth factor-A chain gene. Induction by phorbol ester

Mesangial cells predominantly express platelet-derived growth factor (PDGF)-A chain mRNA and release PDGF. Mesangial cell PDGF-A chain mRNA abundance is regulated by several agents including phorbol esters. We have recently demonstrated that induction of PDGF-A chain mRNA abundance in response to phorbol 12-myristate 13-acetate is primarily due to gene transcription. We have now analyzed the 5'-flanking region of the PDGF-A chain promoter to identify DNA binding protein(s) which have the potential to regulate PDGF-A chain gene transcription in human mesangial cells. DNase I footprint analysis of the 5'-flanking region of the PDGF-A chain promoter identifies a DNase I protected region at the location -82 to -102 corresponding to the sequence 5'-GGCCCGGAATCCGGGGGAGGC-3'. Therefore, nuclear extracts from human mesangial cells contain a protein, PDGF-A-BP-1, that binds to a DNA sequence (-82 to -102) in the promoter region of the PDGF-A chain gene. Gel mobility shift analysis using labeled oligomer corresponding to the binding site for PDGF-A-BP-1 indicates that PDGF-A-BP-1 is induced by phorbol ester in mesangial cells as well as fat-storing cells (> 20 fold). Egr-1 protein does not bind to labeled PDGF-A-BP-1 oligomer and does not compete with the binding of PDGF-A-BP-1. In addition, SP-1 binding sequence does not compete with the binding sequence of the mesangial cell protein. PDGF-A-BP-1 appears to represent a novel protein which is induced by phorbol ester and thus has the potential for an important role in the transcriptional regulation of the PDGF-A chain gene in mesangial cells and other vascular pericytes.

Activation of mesangial cells by the phosphatase inhibitor vanadate. Potential implications for diabetic nephropathy

The metalion vanadate has insulin-like effects and has been advocated for use in humans as a therapeutic modality for diabetes mellitus. However, since vanadate is a tyrosine phosphatase inhibitor, it may result in undesirable activation of target cells. We studied the effect of vanadate on human mesangial cells, an important target in diabetic nephropathy. Vanadate stimulated DNA synthesis and PDGF B chain gene expression. Vanadate also inhibited total tyrosine phosphatase activity and stimulated tyrosine phosphorylation of a set of cellular proteins. Two chemically and mechanistically dissimilar tyrosine kinase inhibitors, genistein and herbimycin A, blocked DNA synthesis induced by vanadate. Vanadate also stimulated phospholipase C and protein kinase C. Downregulation of protein kinase C abolished vanadate-induced DNA synthesis. Thus, vanadate-induced mitogenesis is dependent on tyrosine kinases and protein kinase C activation. The most likely mechanism for the effect of vanadate on these diverse processes involves the inhibition of cellular phosphotyrosine phosphatases. These studies demonstrating that vanadate activates mesangial cells may have major implications for the therapeutic potential of vanadate administration in diabetes. Although vanadate exerts beneficial insulin-like effects and potentiates the effect of insulin in sensitive tissue, it may result in undesirable activation of other target cells, such as mesangial cells.