Interleukin-1 gene cluster polymorphisms predict risk of ESRD

Novel Perspectives in Chronic Kidney Disease-Specific Cardiovascular Disease

Chronic kidney disease (CKD) affects > 10% of the global adult population and significantly increases the risk of cardiovascular disease (CVD), which remains the leading cause of death in this population. The development and progression of CVD-compared to the general population-is premature and accelerated, manifesting as coronary artery disease, heart failure, arrhythmias, and sudden cardiac death. CKD and CV disease combine to cause multimorbid cardiorenal syndrome (CRS) due to contributions from shared risk factors, including systolic hypertension, diabetes mellitus, obesity, and dyslipidemia. Additional neurohormonal activation, innate immunity, and inflammation contribute to progressive cardiac and renal deterioration, reflecting the strong bidirectional interaction between these organ systems. A shared molecular pathophysiology-including inflammation, oxidative stress, senescence, and hemodynamic fluctuations characterise all types of CRS. This review highlights the evolving paradigm and recent advances in our understanding of the molecular biology of CRS, outlining the potential for disease-specific therapies and biomarker disease detection.

Leukocyte-endothelial interaction in CKD

Chronic kidney disease (CKD) represents an independent risk factor for cardiovascular diseases (CVD). Accordingly, CKD patients show a substantial increased risk of cardiovascular mortality. Inflammation represents an important link between CKD and CVD. The interaction between endothelial cells and effector cells of the innate immune system plays a central role in the development and progression of inflammation. Vascular injury causes endothelial dysfunction, leading to augmented oxidative stress, increased expression of leukocyte adhesion molecules and chronic inflammation. CKD induces numerous metabolic changes, creating a uremic milieu resulting in the accumulation of various uremic toxins. These toxins lead to vascular injury, endothelial dysfunction and activation of the innate immune system. Recent studies describe CKD-dependent changes in monocytes that promote endothelial dysfunction and thus CKD progression and CKD-associated CVD. The NLR family pyrin domain containing 3-interleukin-1β-interleukin-6 (NLRP3-IL-1β-IL-6) signaling pathway plays a pivotal role in the development and progression of CVD and CKD alike. Several clinical trials are investigating targeted inhibition of this pathway indicating that anti-inflammatory therapeutic strategies may emerge as novel approaches in patients at high cardiovascular risk and nonresolving inflammation. CKD patients in particular would benefit from targeted anti-inflammatory therapy, since conventional therapeutic regimens have limited efficacy in this population.

Anti-Inflammatory Effects of Peripheral Dopamine

Dopamine is synthesized in the nervous system where it acts as a neurotransmitter. Dopamine is also synthesized in a number of peripheral organs as well as in several types of cells and has organ-specific functions and, as demonstrated more recently, is involved in the regulation of the immune response and inflammatory reaction. In particular, the renal dopaminergic system is very important in the regulation of sodium transport and blood pressure and is particularly sensitive to stimuli that cause oxidative stress and inflammation. This review is focused on how dopamine is synthesized in organs and tissues and the mechanisms by which dopamine and its receptors exert their effects on the inflammatory response.

Innate Immunity System in Patients With Cardiovascular and Kidney Disease

With a global burden of 844 million, chronic kidney disease (CKD) is now considered a public health priority. Cardiovascular risk is pervasive in this population, and low-grade systemic inflammation is an established driver of adverse cardiovascular outcomes in these patients. Accelerated cellular senescence, gut microbiota-dependent immune activation, posttranslational lipoprotein modifications, neuroimmune interactions, osmotic and nonosmotic sodium accumulation, acute kidney injury, and precipitation of crystals in the kidney and the vascular system all concur in determining the unique severity of inflammation in CKD. Cohort studies documented a strong link between various biomarkers of inflammation and the risk of progression to kidney failure and cardiovascular events in patients with CKD. Interventions targeting diverse steps of the innate immune response may reduce the risk of cardiovascular and kidney disease. Among these, inhibition of IL-1β (interleukin-1 beta) signaling by canakinumab reduced the risk for cardiovascular events in patients with coronary heart disease, and this protection was equally strong in patients with and without CKD. Several old (colchicine) and new drugs targeting the innate immune system, like the IL-6 (interleukin 6) antagonist ziltivekimab, are being tested in large randomized clinical trials to thoroughly test the hypothesis that mitigating inflammation may translate into better cardiovascular and kidney outcomes in patients with CKD.

Targeting innate immunity-driven inflammation in CKD and cardiovascular disease

Mortality among patients with chronic kidney disease (CKD) is largely a consequence of cardiovascular disease (CVD) and is a particular concern given the increasing prevalence of CKD. Sterile inflammation triggered by activation of the innate immune system is an important driver of both CKD and associated CVD. Several endogenous mediators, including lipoproteins, crystals such as silica, urate and cholesterol crystals, or compounds released from dying cells interact with pattern recognition receptors expressed on a variety of different cell types, leading to the release of pro-inflammatory cytokines. Disturbed regulation of the haematopoietic system by damage-associated molecular patterns, or as a consequence of clonal haematopoiesis or trained innate immunity, also contributes to the development of inflammation. In observational and genetic association studies, inflammation is linked to the progression of CKD and cardiovascular events. In 2017, the CANTOS trial of canakinumab provided evidence that inhibiting inflammation driven by NLRP3-IL-1-IL-6-mediated signalling significantly reduced cardiovascular event rates in individuals with and without CKD. Other approaches to target innate immune pathways are now under investigation for their ability to reduce cardiovascular events and slow disease progression among patients with atherosclerosis and stage 3 and 4 CKD. This Review summarizes current understanding of the role of inflammation in the pathogenesis of CKD and its associated CVD, and how this knowledge may translate into novel therapeutics.

Association of Interleukin-1 Beta and Interleukin-1 Receptor Antagonist Gene Polymorphisms and Plasma Levels with Diabetic Nephropathy

Objective

We investigated the relationships between interleukin- (IL-) 1β and IL-1 receptor antagonist (IL-1Ra) gene polymorphism and plasma levels in patients with diabetic nephropathy (DN).

Methods

The genotype and allele frequency distribution of IL-1β and IL-1Ra in 61 patients with DN and 48 healthy controls (HCs) were determined by kompetitive allele-specific PCR (KASP), and the plasma concentrations of IL-1β and IL-1Ra in DN patients and HCs were measured by enzyme-linked immunosorbent assays (ELISA).

Results

Significant differences were detected in the distribution of IL-1β (−511C/T) genotype and allele frequencies between the DN and HC groups (P < 0.05), with the T genotype being more frequent in DN patients than HCs (OR = 2.84, 95% CI: 1.489–5.416). The IL-1β (+3953C/T) and IL-1Ra (+8006C/T) genotypes and allele frequencies were not significantly different between the two groups (P > 0.05). The plasma IL-1β level was significantly higher (P < 0.01), while the plasma IL-1Ra concentration was significantly lower in the DN group than the HC group (P < 0.05). Furthermore, the plasma IL-1β level was significantly different between IL-1β (−511C/T) locus variants (P < 0.05).

Conclusion

The IL-1β (−511C/T) gene polymorphism was significantly associated with DN risk in the population of northern Guangxi, China, and the T allele maybe responsible for genetic susceptibility to DN.

Mechanisms of Renal Fibrosis

Tubulointerstitial fibrosis is a chronic and progressive process affecting kidneys during aging and in chronic kidney disease (CKD), regardless of cause. CKD and renal fibrosis affect half of adults above age 70 and 10% of the world's population. Although no targeted therapy yet exists to slow renal fibrosis, a number of important recent advances have clarified the cellular and molecular mechanisms underlying the disease. In this review, I highlight these advances with a focus on cells and pathways that may be amenable to therapeutic targeting. I discuss pathologic changes regulating interstitial myofibroblast activation, including profibrotic and proinflammatory paracrine signals secreted by epithelial cells after either acute or chronic injury. I conclude by highlighting novel therapeutic targets and approaches with particular promise for development of new treatments for patients with fibrotic kidney disease.

What can target kidney fibrosis?

Fibrosis, a characteristic of all chronic kidney diseases, is now recognized to be an independent predictor of disease progression. Deposition of pathological matrix in the walls of glomerular capillaries, the interstitial space and around arterioles both predicts and contributes to functional demise of the nephron and its surrounding vasculature. Recent identification of the major cell populations of fibroblast precursors in the kidney interstitium as pericytes and tissue-resident mesenchymal stem cells, and in the glomerulus as podocytes, parietal epithelial and mesangial cells, has enabled the study of the fibrogenic process in much greater depth directly in the fibroblast precursors. These cells are not only matrix-producing cells, but are also important innate immune surveillance cells that regulate the inflammatory process, exacerbate tissue damage by release of radicals and cytokines, and contribute to parenchymal and microvascular dysfunction by aberrant wound-healing responses. Innate immune signaling in fibroblasts and their precursors is intimately intertwined with the process of fibrogenesis. In addition, genomic and genetic studies also point to defective responses in loci close to genes involved in solute transport, metabolism, autophagy, protein handling and vascular homeostasis, principally in the epithelium and endothelium, as upstream drivers of the fibrotic process, indicating that cellular crosstalk is vital for development of fibrosis. As we move beyond TGFβ inhibition as a central target for fibrosis, targeting innate immune signaling and metabolic dysfunction appear increasingly tenable alternative targets for novel therapies.

Pericyte MyD88 and IRAK4 control inflammatory and fibrotic responses to tissue injury

Fibrotic disease is associated with matrix deposition that results in the loss of organ function. Pericytes, the precursors of myofibroblasts, are a source of pathological matrix collagens and may be promising targets for treating fibrogenesis. Here, we have shown that pericytes activate a TLR2/4- and MyD88-dependent proinflammatory program in response to tissue injury. Similarly to classic immune cells, pericytes activate the NLRP3 inflammasome, leading to IL-1β and IL-18 secretion. Released IL-1β signals through pericyte MyD88 to amplify this response. Unexpectedly, we found that MyD88 and its downstream effector kinase IRAK4 intrinsically control pericyte migration and conversion to myofibroblasts. Specific ablation of MyD88 in pericytes or pharmacological inhibition of MyD88 signaling by an IRAK4 inhibitor in vivo protected against kidney injury by profoundly attenuating tissue injury, activation, and differentiation of myofibroblasts. Our data show that in pericytes, MyD88 and IRAK4 are key regulators of 2 major injury responses: inflammatory and fibrogenic. Moreover, these findings suggest that disruption of this MyD88-dependent pathway in pericytes might be a potential therapeutic approach to inhibit fibrogenesis and promote regeneration.

Of Inflammasomes and Alarmins: IL-1β and IL-1α in Kidney Disease

Kidney injury implies danger signaling and a response by the immune system. The inflammasome is a central danger recognition platform that triggers local and systemic inflammation. In immune cells, inflammasome activation causes the release of mature IL-1β and of the alarmin IL-1α Dying cells release IL-1α also, independently of the inflammasome. Both IL-1α and IL-1β ligate the same IL-1 receptor (IL-1R) that is present on nearly all cells inside and outside the kidney, further amplifying cytokine and chemokine release. Thus, the inflammasome-IL-1α/IL-β-IL-1R system is a central element of kidney inflammation and the systemic consequences. Seminal discoveries of recent years have expanded this central paradigm of inflammation. This review gives an overview of arising concepts of inflammasome and IL-1α/β regulation in renal cells and in experimental kidney disease models. There is a pipeline of compounds that can interfere with the inflammasome-IL-1α/IL-β-IL-1R system, ranging from recently described small molecule inhibitors of NLRP3, a component of the inflammasome complex, to regulatory agency-approved IL-1-neutralizing biologic drugs. Based on strong theoretic and experimental rationale, the potential therapeutic benefits of using such compounds to block the inflammasome-IL-1α/IL-β-IL-1R system in kidney disease should be further explored.

A20 regulates IL-1-induced tolerant production of CXC chemokines in human mesangial cells via inhibition of MAPK signaling

Chemokines and chemokine receptors are involved in the resolution or progression of renal diseases. Locally secreted chemokines mediated leukocyte recruitment during the initiation and amplification phase of renal inflammation. However, the regulation of chemokine induction is not fully understood. In this study, we found that IL-1 induced a significant up-regulation of CXC chemokines CXCL1, 2, and 8 at both mRNA and protein levels in human mesangial cells. The induction of chemokines was tolerant, as the pre-treatment of HMC with IL-1 down-regulated the induction of chemokines induced by IL-1 re-stimulation. IL-1 up-regulated the ubiquintin-editing enzyme A20. A20 over-expression down-regulated IL-1-induced up-regulation of chemokines, and A20 down-regulation reversed chemokine inhibition induced by IL-1 pre-treatment, suggested that A20 played important roles in the tolerant production of chemokines. Unexpectedly, A20 over- expression inhibited the activation of ERK, JNK, and P38, but did not inhibit the activation of NF-κB. In addition, both IL-1 treatment and A20 over-expression induced the degradation of IRAK1, an important adaptor for IL-1R1 signaling, and A20 inhibition by RNA interference partly reversed the degradation of IRAK1. Taken together, IL-1-induced A20 negatively regulated chemokine production, suggesting that A20 may be an important target for the prevention and control of kidney inflammation.

Oxidative stress and its association with TNF-α-308 G/C and IL-1α-889 C/T gene polymorphisms in patients with diabetes and diabetic nephropathy

Diabetic nephropathy is one of the major complications of type 2 diabetes and it is currently the leading cause of end-stage renal disease. The stimulus for the increase in inflammation in diabetes is still under investigation; however, reactive oxygen species might be a primary source. This study was conducted in four groups in West Indian population: control (235), type 2 diabetes (DM) (214), nephropathy with diabetes (DN) (188) and nephropathy without diabetes (NDN) (196). Oxidative stress markers such as malondialdehyde (MDA), glutathione (GSH), superoxide dismutase and catalase were measured in all the groups. TNF-α-308 G/C and IL-1α-889 C/T polymorphisms were analyzed using PCR-RFLP method. Correlations between genotype frequency and the level of oxidative stress markers were examined. MDA was significantly increased in the patient group in comparison to control group. GSH and SOD were significantly decreased in the patient group in comparison to control group. There was no significant difference observed in genotype frequency of TNF-α in the patient group compared with control group. IL-1α-889 C/T polymorphism may be associated with diabetic nephropathy. Moreover there was no association of TNF-α-308 G/C polymorphism with diabetic nephropathy in West Indian population. The higher serum levels of oxidative stress markers in diabetic patients with nephropathy suggest the possible role of oxidative stress.

Interleukin-1 gene cluster variants in hemodialysis patients with end stage renal disease: An association and meta-analysis

We evaluated whether polymorphisms in interleukin (IL-1) gene cluster (IL-1 alpha [IL-1A], IL-1 beta [IL-1B], and IL-1 receptor antagonist [IL-1RN]) are associated with end stage renal disease (ESRD). A total of 258 ESRD patients and 569 ethnicity matched controls were examined for IL-1 gene cluster. These were genotyped for five single-nucleotide gene polymorphisms in the IL-1A, IL-1B and IL-1RN genes and a variable number of tandem repeats (VNTR) in the IL-1RN. The IL-1B − 3953 and IL-1RN + 8006 polymorphism frequencies were significantly different between the two groups. At IL-1B, the T allele of − 3953C/T was increased among ESRD (P = 0.0001). A logistic regression model demonstrated that two repeat (240 base pair [bp]) of the IL-1Ra VNTR polymorphism was associated with ESRD (P = 0.0001). The C/C/C/C/C/1 haplotype was more prevalent in ESRD = 0.007). No linkage disequilibrium (LD) was observed between six loci of IL-1 gene. We further conducted a meta-analysis of existing studies and found that there is a strong association of IL-1 RN VNTR 86 bp repeat polymorphism with susceptibility to ESRD (odds ratio = 2.04, 95% confidence interval = 1.48-2.82; P = 0.000). IL-1B − 5887, +8006 and the IL-1RN VNTR polymorphisms have been implicated as potential risk factors for ESRD. The meta-analysis showed a strong association of IL-1RN 86 bp VNTR polymorphism with susceptibility to ESRD.

Novel gene variants predict serum levels of the cytokines IL-18 and IL-1ra in older adults

Activation of inflammatory pathways measured by serum inflammatory markers such as interleukin-18 (IL-18) and interleukin-1 receptor antagonist (IL-1ra) is strongly associated with the progression of chronic disease states in older adults. Given that these serum cytokine levels are in part a heritable trait, genetic variation may predict increased serum levels. Using the Cardiovascular Health Study and InCHIANTI cohorts, a genome-wide association study was performed to identify genetic variants that influence IL-18 and IL-1ra serum levels among older adults. Multiple linear regression models characterized the association between each SNP and log-transformed cytokine values. Tests for multiple independent signals within statistically significant loci were performed using haplotype analysis and regression models conditional on lead SNP in each region. Multiple SNPs were associated with these cytokines with genome-wide significance, including SNPs in the IL-18-BCO gene region of chromosome 2 for IL-18 (top SNP rs2250417, P=1.9×10(-32)) and in the IL-1 gene family region of chromosome 2 for IL-1ra (rs6743376, P=2.3×10(-26)). Haplotype tests and conditional linear regression models showed evidence of multiple independent signals in these regions. Serum IL-18 levels were also associated with a region on chromosome 2 containing the NLRC4 gene (rs12989936, P=2.7×10(-19)). These data characterize multiple robust genetic signals that influence IL-18 and IL-1ra cytokine production. In particular, the signal for serum IL-18 located on chromosome two is novel and potentially important in inflammasome triggered chronic activation of inflammation in older adults. Replication in independent cohorts is an important next step, as well as molecular studies to better understand the role of NLRC4.

Association of genetic variants with chronic kidney disease in Japanese individuals with or without hypertension or diabetes mellitus

Hypertension and diabetes mellitus are important risk factors for chronic kidney disease (CKD). The purpose of the present study was to identify genetic variants that confer susceptibility to CKD in individuals with or without hypertension or diabetes mellitus, thereby contributing to the personalized prevention of CKD in such individuals separately. The study population comprised 5835 unrelated Japanese individuals, including 1763 subjects with CKD and 4072 controls. The 150 polymorphisms were selected by genome-wide association studies of ischemic stroke and myocardial infarction with the use of the GeneChip Human Mapping 500K Array Set (Affymetrix). The genotypes for these polymorphisms were determined by a method that combines polymerase chain reaction and sequence-specific oligonucleotide probes with suspension array technology. The χ(2) test, multivariable logistic regression analysis with adjustment for covariates, as well as a stepwise forward selection procedure revealed that two different polymorphisms were significantly (P<0.005) associated with the prevalence of CKD in individuals with or without hypertension or diabetes mellitus: the A→G (Lys625Arg) polymorphism of CDH4 (rs6142884) in individuals without diabetes mellitus, and the C→T polymorphism of PTPRN2 (rs1638021) in individuals with hypertension and diabetes mellitus. No polymorphism was significantly associated with CKD in individuals with or without hypertension, in those with diabetes mellitus, or in those without hypertension or diabetes mellitus. Stratification of subjects based on hypertension or diabetes mellitus may thus be fundamental to achieving the personalized prevention of CKD with the use of genetic information.

Association of genetic variants with chronic kidney disease in Japanese individuals

BACKGROUND AND OBJECTIVES

Although genetic linkage analyses and association studies have implicated several loci and candidate genes in predisposition to chronic kidney disease (CKD), the genes that underlie genetic susceptibility to this condition have remained uncharacterized. The purpose of the present study was to identify genetic variants that confer susceptibility to CKD in Japanese individuals.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The study population comprised 5217 Japanese individuals (2955 men, 2262 women), including 778 subjects (480 men, 298 women) with CKD [estimated GFR (eGFR), <50 ml min(-1) 1.73 m(-2)] and 4439 controls (2475 men, 1964 women; eGFR, > or =60 ml min(-1) 1.73 m(-2)). The genotypes for 40 polymorphisms of 32 candidate genes were determined.

RESULTS

The chi-square test and multivariable logistic regression analysis with adjustment for covariates revealed that the -219G-->T polymorphism of APOE, the -519A-->G of MMP1, the -866G-->A of UCP2, the -1607/1G-->2G of MMP1, the A-->G (Lys45Glu) of MMP3, the G-->A (Ala163Thr) of AGTR1, the G-->A (Gly670Arg) of PECAM1, and the -55C-->T of UCP3 were significantly (false discovery rate <0.05) associated with CKD. Comparison of allele frequencies of these polymorphisms by the chi-square test between subgroups of CKD and control subjects individually matched for covariates revealed that the -519A-->G of MMP1 and the -866G-->A of UCP2 were significantly (P < 0.05) associated with CKD.

CONCLUSIONS

MMP1 and UCP2 may be susceptibility loci for CKD in Japanese individuals. Determination of genotypes for these polymorphisms may prove informative for prediction of genetic risk for CKD.

Associations of interleukin-6, C-reactive protein and serum amyloid A with mortality in haemodialysis patients

BACKGROUND

Individuals with end-stage renal disease (ESRD) manifest a chronic inflammatory state. Serum albumin, C-reactive protein (CRP), interleukin-6 (IL-6) and serum amyloid A (SAA) have been associated with mortality in ESRD, although reports vary as to whether they are true independent markers of mortality. We undertook a prospective study to determine whether these markers could predict mortality in ESRD.

METHODS

A cohort of individuals on haemodialysis was followed prospectively for a mean of 2.1 years. Albumin, CRP, IL-6 and SAA were drawn at enrollment. Association between mortality and serum markers was assessed using Cox proportional hazards regression. A trend analysis was undertaken to establish the functional form of the association between serum markers and outcome.

RESULTS

After multivariable adjustment, IL-6 was most strongly associated with mortality, followed closely by albumin (P = 0.0002 and P = 0.0005, respectively). CRP was marginally associated with mortality (P = 0.046), and SAA was not independently associated with mortality. In the final model adjusting for the effects of both IL-6 and albumin simultaneously, both markers remained associated with mortality (P = 0.003 and P = 0.011).

CONCLUSION

IL-6 had the strongest independent association with mortality, followed closely by albumin. CRP and SAA were not associated with mortality when measured at single time points. Increasing levels of IL-6 and decreasing levels of albumin were associated with increased mortality. IL-6 and albumin may be capturing different aspects of the inflammatory burden observed in haemodialysis patients.

Interleukin-1beta, but not interleukin-6, enhances renal and systemic endothelin production in vivo

The inflammatory cytokines IL-1beta and IL-6 have been shown to stimulate production of endothelin-1 (ET-1) by several cell types in vitro, but their effects on renal ET-1 production in vivo are not known. To test whether IL-1beta and IL-6 stimulate renal ET-1 production and release in vivo, urine was collected from male C57BL/6 mice over 24-h periods at baseline and on days 7 and 14 of a 14-day subcutaneous infusion of IL-1beta (10 ng/h), IL-6 (16 ng/h), or vehicle. By day 14, plasma ET-1 was significantly increased by IL-1beta infusion (1.7 +/- 0.1 vs. 0.8 +/- 0.1 pg/ml for vehicle, P < 0.001). Compared with vehicle infusion, IL-1beta infusion induced significant increases in urinary ET-1 excretion rate and urine flow but did not affect conscious mean arterial pressure (telemetry). IL-1beta infusion significantly increased renal cortical and medullary IL-1beta content (ELISA) and prepro-ET-1 mRNA expression (quantitative real-time PCR). In contrast, 14 days of IL-6 infusion had no significant effect on plasma ET-1 or urinary ET-1 excretion rate. To determine whether IL-1beta stimulates ET-1 release via activation of NF-kappaB, inner medullary collecting duct (IMCD-3) cells were incubated for 24 h with IL-1beta, and ET-1 release and NF-kappaB activation were measured (ELISA). IL-1beta activated NF-kappaB and increased ET-1 release in a concentration-dependent manner. The effect of IL-1beta on ET-1 release could be partially inhibited by pretreatment of IMCD-3 cells with an inhibitor of NF-kappaB activation (BAY 11-7082). These results indicate that IL-1beta stimulates renal and systemic ET-1 production in vivo, providing further evidence that ET-1 participates in inflammatory responses.

Arterial calcification: a tumor necrosis factor-alpha mediated vascular Wnt-opathy

Arterial calcification is common in patients with type 2 diabetes mellitus (DM), chronic kidney disease (CKD), and other chronic inflammatory disorders. Arterial calcification is associated with significant morbidity and increased early mortality. The molecular signature of vascular calcification in diabetes is strikingly similar to that of CKD. Low-grade arterial inflammation is common to both conditions, and increased levels of tumor necrosis factor-alpha (TNF-alpha) have been reported in both DM and CKD. Recently, we described a novel TNF-alpha regulated Msx2-Wnt osteogenic program that regulates arterial calcification in an animal model of type 2 DM. TNF-alpha induces the osteogenic bone morphogenetic protein-2 (BMP-2), Msx2, Wnt3a, and Wnt7a mRNAs and leads to increased aortic calcium accumulation. Treatment with the TNF-alpha neutralizing antibody infliximab abrogates aortic BMP-2-Msx2-Wnt3a and Wnt7a signaling and attenuates aortic calcium accumulation significantly. Mice with vascular TNF-alpha augmented by the SM22-TNF-alpha transgene upregulate the aortic Msx2-Wnt3a/Wnt7a axis. Furthermore, SM22-TNF-alphaTg;TOPGAL mice exhibit greater beta-galactosidase reporter staining versus TOPGAL siblings in the aorta and coronaries, which indicates enhanced mural Wnt signaling in response to TNF-alpha. Thus, inflammatory TNF-alpha signals promote aortic osteogenic Msx2-Wnt programs in type 2 DM, and arterial calcification in this model is a TNF-alpha-driven Wnt-opathy. Having established the role of TNF-alpha in diabetic vascular calcification, an unmet need exists to evaluate the role of TNF-alpha and Msx2-Wnt signals in CKD-related calcification models. If validated in these models, then these findings will have significant therapeutic applications.

Genetic polymorphisms of the RAS-cytokine pathway and chronic kidney disease

Chronic kidney disease (CKD) in children is irreversible. It is associated with renal failure progression and atherosclerotic cardiovascular (CV) abnormalities. Nearly 60% of children with CKD are affected since birth with congenital or inherited kidney disorders. Preliminary evidence primarily from adult CKD studies indicates common genetic risk factors for CKD and atherosclerotic CV disease. Although multiple physiologic pathways share common genes for CKD and CV disease, substantial evidence supports our attention to the renin angiotensin system (RAS) and the interlinked inflammatory cascade because they modulate the progressions of renal and CV disease. Gene polymorphisms in the RAS-cytokine pathway, through altered gene expression of inflammatory cytokines, are potential factors that modulate the rate of CKD progression and CV abnormalities in patients with CKD. For studying such hypotheses, the cooperative efforts among scientific groups and the availability of robust and affordable technologies to genotype thousands of single nucleotide polymorphisms (SNPs) across the genome make genome-wide association studies an attractive paradigm for studying polygenic diseases such as CKD. Although attractive, such studies should be interpreted carefully, with a fundamental understanding of their potential weaknesses. Nevertheless, whole-genome association studies for diabetic nephropathy and future studies pertaining to other types of CKD will offer further insight for the development of targeted interventions to treat CKD and associated atherosclerotic CV abnormalities in the pediatric CKD population.

Interleukin-1 receptor antagonist gene polymorphism affects the progression of chronic renal failure

End-stage renal disease (ESRD) involves an inflammatory process. Interleukin-1 receptor antagonist (IL-1Ra) and interleukin-1beta gene polymorphisms affect susceptibility to the disease in several inflammatory diseases. We investigated whether these polymorphisms are involved in ESRD by genotyping DNA from 602 dialyzed patients and 433 controls with polymerase chain reaction and digestion with restriction endonuclease. Allele 2 of the IL-1Ra VNTR polymorphism was associated with ESRD (OR=1.46, 95% CI 1.19-1.78). We also found a strong association between this allele and recurrent peritonitis in peritoneal dialysis patients. Odds ratio for the risk allele was higher compared to entire ESRD group (OR=3.6, 95% CI 1.70-7.44). The homozygosity for the allele 2 was associated with disease progression, especially in patients with diabetic nephropathy and glomerulonephritis. For the patients from these two subgroups having 2.2 genotype, the mean time from disease onset to ESRD was 1.5 and 2.2 years, respectively, compared to 6.4 and 9.8 years for those with 1.1 genotype. The IL-1Ra allele 2 is associated with ESRD in our dialyzed patients. Our results demonstrate for the first time the association of the IL-1Ra allele 2 with faster progression to ESRD. If confirmed in other populations, it might be a predictor of faster disease progression.

Interleukin-1beta and receptor antagonist (IL-1Ra) gene polymorphisms and the prediction of the risk of end-stage renal disease

Cytokines play an important role in the pathogenesis of kidney disease and its progression to end-stage renal disease (ESRD). Inflammation is regulated by the genes of the interleukin 1 (IL-1) gene cluster. Therefore, it was hypothesized that a polymorphism in this gene cluster may be associated with the risk of ESRD. Polymorphisms in the IL-1 gene cluster were examined in a cohort of 222 ESRD patients and 206 controls of similar ethnicity. These individuals were genotyped for IL-1 beta (promoter -511 and exon-5 +3953) genes and a variable number of tandem repeats (VNTR) in the IL-1 receptor antagonist gene (IL-1Ra). There was significant difference in genotype frequencies between ESRD patients and control group for IL-1beta (promoter region and exon-5) and IL-1Ra gene polymorphism (p < 0.001, 0.006 and < 0.001, respectively). A significant difference was observed in IL-1Ra for 1/1 (410/410) and 1/2 (410/240) genotypes, and the risk for ESRD was higher in those carrying the 1/1 genotype (p = 0.014, OR = 1.692, and p < 0.001, OR = 0.163). Also identified was a novel, rare allele of a single copy of 86 bp in ESRD patients as compared with the controls. The haplotype 'T-E2-1' frequency distribution between patients and controls revealed greater than threefold risk (p = 0.001, OR = 3.572, 95% CI = 1.589-8.032). Genetic linkage between the IL-1beta promoter region and exon-5 and between the IL-1beta promoter and IL-1Ra of IL-1 gene demonstrated a strong association among the variants in controls (D' = 0.42, p < 0.001, and D' = 0.39, p=0.001). Thus, the three polymorphisms within the IL-1 cluster are associated with ESRD. This finding is perhaps one of the strongest associations between genotype and ESRD reported, and it suggests that the IL-1 gene cluster affects the risk of development of ESRD.

Genetic association of interleukin-1β and receptor antagonist (IL-1Ra) gene polymorphism with allograft function in renal transplant patients

Cytokines are known to be important mediators during renal graft outcome. The present study was therefore, conducted to determine the impact of IL-1beta and its receptor antagonist polymorphism on allograft outcome. We evaluated single nucleotide polymorphism (SNPs) in interleukin-1 gene cluster, IL-1beta (promoter region -511 and exon-5 +3954) and IL-1Ra (86-bp VNTR) in 136 renal transplant recipients and 150 normal healthy controls by polymerase chain restriction based (PCR-RFLP) analysis. Recipients were HLA matched and clinically characterized including delayed graft function (DGF), rejection episode (RE) and stable graft function (SGF). Haplotypes and linkage disequilibrium (LD) were determined using SNPAnalyzer software. Significant difference was observed for the frequency distribution of the three sites of IL-1 gene among patients and controls (p<0.001, 0.022 and <0.001 respectively). When RE and DGF were compared to SGF, only IL-1Ra showed significant differences among RE and SGF (p=0.014) and DGF and SGF (p=0.020). The presence of 1/2 genotype showed 18 folds risk in RE and 10 folds in DGF (OR=18.000 and OR=10.667 respectively). The majority of recipients with SGF had 1-4 HLA mismatch whereas RE had 5-8 mismatches. Risk for rejection increased >6 folds (OR=6.571; p<0.01) for 5-8 mismatches. Haplotypes constructed with the combination of three polymorphisms in IL-1 gene cluster showed significant difference between RE and SGF group. LD value for IL-1beta (promoter region) and IL-1Ra and IL-1beta promoter and exon-5 gene in the control group indicated strong association among the variants (D'=0.37, p<0.0001 and D'=0.29, p=0.002). Our study demonstrate that genetically determined low production of IL-1Ra may be a risk factor for RE and DGF and that IL-1beta/IL-1Ra haplotype influences the impact of allograft outcome. These findings may significantly abet in better perception of the survival of the graft.

Differential regulation of endothelial cell activation by complement and interleukin 1alpha

Activation of complement on endothelium triggers physiological changes that promote coagulation, thrombosis, and inflammation. Unlike agonists such as cytokines and endotoxin that induce these changes through transcription of many genes, complement, particularly the membrane attack complex, primarily induces release of IL-1alpha by the endothelial cells; the cytokine may then be removed by normal blood flow or may promote activation of the full range of endothelial cell responses in an autocrine or paracrine manner. We studied the intracellular signaling pathways used by complement to activate interleukin (IL)-1alpha transcription in cultured endothelial cells. The membrane attack complex and other pore-forming proteins stimulated calcineurin and activated selective transcription of the IL-1alpha gene. In contrast, the action of cytokines such as IL-1alpha was not selective and not dependent on calcineurin activity. Transcription of IL-1alpha, whether stimulated by complement and calcineurin or by "conventional agonists," such as IL-1alpha independent of calcineurin, proceeded via binding of nuclear factor kappaB transcriptional activators to the IL-1alpha gene promoter. These findings define a molecular mechanism through which complement regulates IL-1alpha production by endothelial cells and explain how blood flow may determine the extent of complement-stimulated inflammation.