The long pentraxin PTX3 is synthesized in IgA glomerulonephritis and activates mesangial cells

Assessing the Inhibitory Potential of Pregnenolone Sulfate on Pentraxin 3 in Diabetic Kidney Disease: A Molecular Docking and Simulation Study

Diabetic Kidney Disease (DKD), a frequent consequence of diabetes, has substantial implications for both morbidity and mortality rates, prompting the exploration of new metabolic biomarkers due to limitations in current methods like creatinine and albumin measurements. Pentraxin 3 (PTX3) shows promise for assessing renal inflammation in DKD. This study investigates how DKD metabolites could influence PTX3 expression through molecular docking, ADMET profiling, and dynamic simulation. Network and pathway analyses were conducted to explore metabolite interactions with DKD genes and their contributions to DKD pathogenesis. Thirty-three DKD-associated metabolites were screened, using pentoxifylline (PEN) as a reference. The pharmacokinetic properties of these compounds were evaluated through molecular docking and ADMET profiling. Molecular dynamics simulations over 200 ns assessed the stability of PTX3 (apo), the PRE-PTX3 complex, and PEN-PTX3 across multiple parameters. Cytoscape identified 1082 nodes and 1381 edges linking metabolites with DKD genes. KEGG pathway analysis underscored PTX3's role in inflammation. Molecular docking revealed pregnenolone sulfate (PRE) with the highest binding affinity (-6.25 kcal/mol), followed by hydrocortisone (-6.03 kcal/mol) and 2-arachidonoylglycerol (-5.92 kcal/mol), compared to PEN (-5.35 kcal/mol). ADMET profiling selected PRE for dynamic simulation alongside PEN. Analysis of RMSD, RMSF, RG, SASA, H-bond, PCA, FEL, and MM-PBSA indicated stable complex behavior over time. Our findings suggest that increasing PRE levels could be beneficial in managing DKD, potentially through isolating PRE from fungal sources, synthesizing it as dietary supplements, or enhancing endogenous PRE synthesis within the body.

The pentraxin family in autoimmune disease

The pentraxins represent a family of multifunctional proteins composed of long and short pentamers. The latter includes serum amyloid P component (SAP) and C-reactive protein (CRP) whereas the former includes neuronal PTX1 and PTX2 (NPTX1 and NPTX2, respectively), PTX3 and PTX4. These serve as a bridge between adaptive immunity and innate immunity and a link between inflammation and immunity. Similarities and differences between long and short pentamers are examined and their roles in autoimmune disease are discussed. Increased CRP and PTX3 could indicate the activity of rheumatoid arthritis, systemic lupus erythematosus or other autoimmune diseases. Mechanistically, CRP and PTX3 may predict target organ injury, regulate bone metabolic immunity and maintain homeostasis as well as participate in vascular endothelial remodeling. Interestingly, PTX3 is pleiotropic, being involved in inflammation and tissue repair. Given the therapeutic potential of PTX3 and CRP, targeting these factors to exert a beneficial effect is the focus of research efforts. Unfortunately, studies on NPTX1, NPTX2, PTX4 and SAP are scarce and more research is clearly needed to elaborate their potential roles in autoimmune disease.

Pentraxin-3 - a potential biomarker in ANCA-associated vasculitis

OBJECTIVE

The aim of this study was to investigate pentraxin-3 (PTX3) as a potential biomarker of inflammatory activity in patients with anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) at baseline and 6 month follow-up in a longitudinal cohort.

METHOD

Plasma PTX3 levels were measured in 79 newly diagnosed or relapsing AAV patients at baseline and 6 month follow-up, and in 23 healthy controls. Urinary PTX3 levels were measured in 34 of the patients. C-reactive protein (CRP), creatinine, and albuminuria were measured and the cumulative glucocorticoid dose at inclusion was calculated. The Birmingham Vasculitis Activity Score (BVAS) was assessed at baseline and follow-up.

RESULTS

Plasma PTX3 levels were significantly higher at baseline than at 6 months (2.85 vs 1.23 ng/mL, p < 0.001). Plasma and urinary PTX3 levels correlated with BVAS at baseline (ρ = 0.45, p < 0.001, and ρ = 0.49, p = 0.008, respectively). A significant correlation between both plasma and urinary PTX3 levels and estimated glomerular filtration rate and albuminuria was found. However, there was no correlation between plasma and urinary PTX3 levels. At baseline, plasma and urinary PTX3 levels were significantly higher in patients with kidney involvement. PTX3 levels did not correlate with CRP, nor was there a correlation between CRP levels and BVAS at baseline.

CONCLUSION

Plasma and urinary PTX3 seem to reflect disease activity in AAV better than the commonly used CRP. PTX3 may have a potential role as a biomarker in monitoring disease activity in AAV patients, particularly in patients with kidney involvement.

Periodontitis Exacerbates and Promotes the Progression of Chronic Kidney Disease Through Oral Flora, Cytokines, and Oxidative Stress

Periodontitis is a type of systemic immune inflammation that is caused by the complex infection of a variety of microorganisms in the subgingival plaque and the imbalance of the microbial ecological environment in the mouth. Periodontitis and chronic kidney disease (CKD) share many risk factors, such as obesity, smoking, and age. A growing body of data supports a strong correlation between periodontitis and kidney disease. Evidence supports the role of periodontal inflammation and elevated serum inflammatory mediators in renal atherosclerosis, renal deterioration, and end-stage renal disease (ESRD) development. Periodontitis is a risk factor for kidney disease. However, to our knowledge, there are few studies detailing the possible link between periodontitis and CKD. This review summarizes the possible mechanisms underlying periodontitis and CKD. More importantly, it highlights novel and potential pathogenic factors for CKD, including bacteria, pro-inflammatory mediators and oxidative stress. However, most research on the relationship between periodontitis and systemic disease has not determined causality, and these diseases are largely linked by bidirectional associations. Future research will focus on exploring these links to contribute to new treatments for CKD.

Empagliflozin Inhibits IL-1β-Mediated Inflammatory Response in Human Proximal Tubular Cells

SGLT2 inhibitor-related nephroprotection is—at least partially—mediated by anti-inflammatory drug effects, as previously demonstrated in diabetic animal and human studies, as well as hyperglycemic cell culture models. We recently presented first evidence for anti-inflammatory potential of empagliflozin (Empa) under normoglycemic conditions in human proximal tubular cells (HPTC) by demonstrating Empa-mediated inhibition of IL-1β-induced MCP-1/CCL2 and ET-1 expression on the mRNA and protein level. We now add corroborating evidence on a genome-wide level by demonstrating that Empa attenuates the expression of several inflammatory response genes in IL-1β-induced (10 ng/mL) normoglycemic HPTCs. Using microarray-hybridization analysis, 19 inflammatory response genes out of >30.000 human genes presented a consistent expression pattern, that is, inhibition of IL-1β (10 ng/mL)-stimulated gene expression by Empa (500 nM), in both HK-2 and RPTEC/TERT1 cells. Pathway enrichment analysis demonstrated statistically significant clustering of annotated pathways (enrichment score 3.64). Our transcriptomic approach reveals novel genes such as CXCL8/IL8, LOX, NOV, PTX3, and SGK1 that might be causally involved in glycemia-independent nephroprotection by SGLT2i.

Pentraxin 3: A promising therapeutic target for autoimmune diseases

Pentraxin 3 (PTX3) is a prototypic humoral soluble pattern recognition molecule that exerts a pivotal role in innate immune response and inflammation, as well as in tissue damage and remodeling. Recently, emerging evidence has revealed that PTX3 is involved in the occurrence and development of various autoimmune diseases, such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), ankylosing spondylitis (AS), systemic sclerosis (SSc), inflammatory bowel disease (IBD), multiple sclerosis (MS) and psoriasis, etc. In this review, we have succinctly summarized the complex immunological functions of PTX3 and mostly focused on recent findings of the pleiotropic activities played by PTX3 in the pathogenesis of autoimmune diseases, aiming at hopefully offering possible future therapeutic alternatives.

Is pentraxin 3 level an effective biomarker in disease activity in patients with rheumatoid arthritis?

INTRODUCTION

The aim of the current study was to identify whether serum pentraxin 3 (PTX3) level could be a marker of increased inflammation in rheumatoid arthritis (RA) patients.

MATERIAL AND METHODS

The study included 41 patients diagnosed with RA according to the American College of Rheumatology (ACR) 1990 diagnostic criteria. We compared the serum PTX3 levels between RA patients and a healthy control group, the relationship between PTX3 level and disease activity was also examined.

RESULTS

A statistically significant difference was determined between the RA patients and controls as regards PTX3, platelets, C-reactive protein, and mean platelet volume results (p = 0.042, p = 0.007, p = 0.017, p < 0.001, respectively). There was no statistically significant difference in terms of PTX3 level between anti-CCP-positive and -negative patients (p = 0.368). No statistically significant difference was determined in respect of PTX3 levels between RA patients with different disease activity scores (p = 0.346).

CONCLUSIONS

No relationship was determined between PTX3 and disease activity in RA patients, nor with traditional clinical and biochemical measurements of disease activity. However, the PTX3 levels of the RA patients were found to be high in comparison with the control group. Because, from these results, the role of PTX3 in the pathogenesis of RA cannot be ignored, there is a need for further studies to determine the potential role of PTX3 in RA pathogenesis.

Investigation of the Mechanism Underlying Calcium Dobesilate-Mediated Improvement of Endothelial Dysfunction and Inflammation Caused by High Glucose

Background/Aims

Diabetic kidney disease (DKD) is a leading cause of end-stage renal disease. Calcium dobesilate (CaD) is widely used to treat diabetic retinopathy. Recent studies have demonstrated that CaD exerts protective effects against diabetic nephropathy. The aim of this study was to elucidate the molecular and cellular mechanisms underlying the protective effects of CaD.

Methods

Human umbilical vein endothelial cells (HUVECs) were cultured with different D-glucose concentrations to determine the effects of high glucose on HUVEC gene expression. HUVECs were also incubated with CaD (25 μM, 50 μM, and 100 μM) for 3 days to determine the effects of CaD on HUVEC viability. db/db mice were treated with CaD. 2-[(Aminocarbonyl)amino]-5-(4-fluorophenyl)-3-thiophenecarboxamide (TPCA-1) blocked the nuclear factor-κB (NF-κB) pathway in HUVECs. A pentraxin 3 (PTX3) small interfering RNA (siRNA) intervention experiment was performed in the cells. An adenovirus-encapsulated PTX3 siRNA intervention experiment was performed in db/db mice. Western blot and real-time PCR analyses were used to detect PTX3, p-IKBa/IKBa (I-kappa-B-alpha), and p-eNOS/eNOS (endothelial nitric oxide synthase) expression in mice and HUVECs. Hematoxylin-eosin (HE) staining and periodic acid-Schiff (PAS) staining were used to observe renal tissue damage in mice. PTX3 expression was observed by immunohistochemical staining.

Results

CaD downregulated the expression of PTX3 and p-IKBa/IKBa and upregulated the expression of p-eNOS/eNOS in vitro. When TPCA-1 was used, high glucose induced high PTX3 expression, and the expression of p-eNOS/eNOS increased. After PTX3 gene silencing, the expression of p-eNOS/eNOS also increased. In vivo, CaD reduced the expression of PTX3 and p-IKBa/IKBa in the kidneys of db/db mice and increased the expression of p-eNOS/eNOS. After PTX3 gene silencing, the urine protein and renal function of db/db mice were ameliorated, the glomerular extracellular matrix was decreased, and the expression of p-eNOS/eNOS was increased.

Conclusions

Our results suggested that CaD may inhibit the expression of PTX3 by altering the IKK/IKB/NF-κB pathway, thereby improving endothelial dysfunction in HUVECs. PTX3 may be a potential therapeutic target for DKD.

Quercetin reduces TNF-α-induced mesangial cell proliferation and inhibits PTX3 production: Involvement of NF-κB signaling pathway

Lupus nephritis (LN) is an autoimmune disease caused by systemic lupus erythematosus. Excessive proliferation of mesangial cells is one of the most serious pathological manifestations of LN. In addition, the expression of PTX3 is elevated in the serum of patients with LN. Quercetin has good anti-inflammatory effects and immunomodulatory activities. In this study, the result of MTT indicated that quercetin treatment alleviated the excessive proliferation of mesangial cells. ELISA and immunofluorescence experiments showed that quercetin treatment inhibited the expression of PTX3. Three doses of quercetin (20, 40, and 80 μM) were selected for the experiment. It is noteworthy that the efficacy of quercetin at 80 μM was significantly better than that of other dose groups. And the effect in inhibiting PTX3 expression was comparable with that of the PDTC (80 μM) positive control. Western blot and qRT-PCR analysis revealed that quercetin treatment reduced the expression of nuclear factor-κB p65 and IKKβ, increased the expression of IκBα, and inhibited the expression of PTX3. In conclusion, through inhibiting the activation of nuclear factor-κB signaling pathway, quercetin treatment could reduce the expression of PTX3 and inhibit the excessive proliferation of mesangial cells, suggesting that quercetin is a potential therapeutic drug for LN.

Pentraxin 3 deficiency exacerbates lipopolysaccharide-induced inflammation in adipose tissue

BACKGROUND/OBJECTIVES

Pentraxin 3 (PTX3) has been characterized as a soluble and multifunctional pattern recognition protein in the regulation of innate immune response. However, little is known about its role in adipose tissue inflammation and obesity. Herein, we investigated the role of PTX3 in the regulation of lipopolysaccharide (LPS)-induced inflammation in adipocytes and adipose tissue, as well as high-fat diet (HFD)-induced metabolic inflammation in obesity.

METHODS

Ptx3 knockdown 3T3-L1 Cells were generated using shRNA for Ptx3 gene and treated with different inflammatory stimuli. For the in vivo studies, Ptx3 knockout mice were treated with 0.3 mg/kg of LPS for 6 h. Adipose tissues were collected for gene and protein expression by qPCR and western blotting, respectively. Ptx3 knockout mice were fed with HFD for 12 week since 6 week of age.

RESULTS

We observed that the expression of PTX3 in adipose tissue and serum PTX3 were markedly increased in response to LPS administration. Knocking down Ptx3 in 3T3-L1 cells reduced adipogenesis and caused a more profound and sustained upregulation of proinflammatory gene expression and signaling pathway activation during LPS-stimulated inflammation in 3T3-L1 adipocytes. In vivo studies showed that PTX3 deficiency significantly exacerbated the LPS-induced upregulation of inflammatory genes and downregulation of adipogeneic genes in visceral and subcutaneous adipose tissue of mice. Accordingly, LPS stimulation elicited increased activation of nuclear factor-κB (NF-κB) and p44/42 MAPK (Erk1/2) signaling pathways in visceral and subcutaneous adipose tissue. The expression of PTX3 in adipose tissue was also induced by HFD, and PTX3 deficiency led to the upregulation of proinflammatory genes in visceral adipose tissue of HFD-induced obese mice.

CONCLUSIONS

Our results suggest a protective role of PTX3 in LPS- and HFD-induced sustained inflammation in adipose tissue.

Urinary excretion of pentraxin-3 correlates with the presence of renal scar following acute pyelonephritis in children

PURPOSE

Acute pyelonephritis is associated with considerable morbidity and potential for renal scarring. Pentraxin3 (PTX3) is a recently discovered mediator of inflammation. The objective of this study was to investigate the changes in serum and urine PTX3 levels in children who had a history of pyelonephritis and were diagnosed with renal parenchymal scar (RPS) and/or vesicoureteral reflux (VUR).

METHODS

The study included 88 children (31 males, 57 females) aged between 3 months and 18 years. The children included in the study were divided into four groups: VUR with RPS (Group 1), RPS without VUR (Group 2), VUR without RPS (Group 3), and healthy children without a history of hydronephrosis or UTI history (Group 4). After the initial evaluation, the participants were further divided into two more groups and re-evaluated: Children with RPS (Group 1 + 2), children without RPS (Group 3 + 4), children with VUR (Group 1 + 3), and children without VUR (Group 2 + 4).

RESULTS

We found that urine pentraxin 3 (uPTX3) and uPTX3/Creatinine levels were significantly higher in the groups with renal scar with or without VUR than the ones without RPS [mean uPTX3, 3.5 pg/ml (min-max 0.0022-12.3668) vs. 2.2 pg/ml (min-max 0.0022-18.5868) and uPTX3/creatinine, 10.5 pg/mg (min-max 0.0035-51.1) vs. 5.8 pg/mg (min-max 0.0004-78.7), p < 0.01]. uPTX3 levels were not different among the groups with and without VUR. In addition, serum PTX3 levels were not different among the groups.

CONCLUSIONS

We showed that urinary PTX3 increased only in patients with scarred kidneys. These results might be helpful to predict RPS due to past pyelonephritis.

Circulating Pentraxin3-Specific B Cells Are Decreased in Lupus Nephritis

Background: Pentraxin3 (PTX3) is overexpressed in kidneys of patients developing lupus nephritis (LN). Active LN is associated with reduced anti-PTX3 antibodies. However, abnormalities of B cell differentiation against PTX3 have not been characterized in systemic lupus erythematosus (SLE).

Objective: Characterization of PTX3-specific (PTX3⁺) B cells in peripheral blood of SLE patients with or without LN and healthy donors (HD).

Patients and Methods: SLE patients without LN, biopsy-proven LN and matched HD were analyzed. Active LN was defined as proteinuria>0.5 g/day or CrCl<60 ml/min/1.73 m² with active urinary sediment. Peripheral B cells were analyzed for direct PTX3 binding by flow cytometry using PTX3 labeled with cyanine 5 (Cy5) and phycoerythrin (PE).

Results: Initially, a flow cytometry based assay to identify PTX3⁺ B cells was developed by demonstrating simultaneous binding of PTX3-Cy5 and PTX3-PE. Specificity of B cells was validated by blocking experiments using unlabeled PTX3. We could identify circulating PTX3⁺ B-cells in HD and patients. Notably, LN patients showed a significantly diminished number of PTX3⁺ B cells (SLE vs. LN p = 0.033; HD vs. LN p = 0.008). This decrease was identified in naïve and memory B cell compartments (naïve: SLE vs. LN p = 0.028; HD vs. LN p = 0.0001; memory: SLE vs. LN p = 0.038, HD vs. LN p = 0.011).

Conclusions: Decreased PTX3⁺ B cells in LN within the naïve and memory compartment suggest their negative selection at early stages of B cell development potentially related to a decreased regulatory function. PTX3⁺ B cells could candidate for autoantigen-defined regulatory B cells as a striking abnormality of LN patients.

Exogenous pentraxin-3 inhibits the reactive oxygen species-mitochondrial and apoptosis pathway in acute kidney injury

Pentraxin-3 (PTX3) is a long-form member of the pentraxin family of proteins that has been studied in inflammatory diseases and in various organs. We found that PTX3 protects kidney cells during ischemia and proinflammatory acute kidney injury. The aim of this study was to develop an in vitro experimental model of acute kidney injury and to analyze the protective mechanism of exogenous recombinant PTX3. In this study, cells of the HK-2 renal tubular cell line were treated with a calcium ionophore (A23187), which induced injury by increasing intracellular calcium concentrations and inducing calpain activity and the generation of reactive oxygen species. Exposure of cells to PTX3 significantly attenuated these effects. In addition, the activity of caspase-3 and PARP-1 were decreased in ischemic cells exposed to exogenous recombinant PTX3. PTX3 stabilized the mitochondrial membrane potential and suppressed apoptosis, resulting in the protection of renal tubular cells from ischemic injury.

PTX3 in serum induces renal mesangial cell proliferation but has no effect on apoptosis

The present study aimed to investigate the effect of pentraxin 3 (PTX3) on the regulation of proliferation and apoptosis in human glomerular mesangial cells (HMCs). Small interfering (si)RNA was designed and synthesized to inhibit the expression of endogenous PTX3, and the effects on the proliferation and apoptosis of HMCs were detected by flow cytometry and an MTT assay. Western blot analysis was used to detect the activation of mitogen-activated protein kinase (MAPK) proteins in HMCs with PTX3 knockdown. Three siRNAs targeting PTX3 were individually transfected into HMCs for 48 h, and reverse-transcription quantitative PCR demonstrated that the relative mRNA expression of PTX3 was significantly decreased in all groups by up to 79.62% of that in the control group (P<0.05). Following transfection with PTX3-siRNA, the viability of an HMC line was significantly decreased in comparison with that of a control group transfected with scrambled siRNA. However, PTX3-siRNA did not significantly effect early and late apoptotic cell populations in HMCs compared with those in the control. Endogenous PTX3 interference was found to significantly decrease p38 MAPK, extracellular signal-regulated kinase 1/2 and c-Jun N-terminal kinase phosphorylation. In conclusion, silencing of PTX3, inhibited the proliferation of HMCs via MAPK pathways, but exerted no effect on the apoptosis of HMCs.

Study on Association of Pentraxin 3 and Diabetic Nephropathy in a Rat Model

Diabetic nephropathy (DN) is a serious microvascular complication of diabetes. Compared with other therapies for diabetic patients, islet transplantation can effectively prevent and reverse diabetes-induced microvascular disease, such as diabetic retinopathy and nephropathy. PTX3 is the only long pentraxin that can be detected in renal tissue. In this study, we investigated the expression of PTX3 when early DN was reversed after islet transplantation. Methods. Diabetes was induced in rats by injecting streptozotocin (STZ). Twelve weeks later, the diabetic rats were divided into 2 groups: the islet transplantation group (IT) and the diabetic nephropathy group (DN). Renal injury, renal function, and the expression of PTX3 in the plasma and the kidneys were assessed with urinalysis, immunohistochemical staining, and Western blot, respectively. Results. The expression of PTX3 in the kidney was significantly decreased in the DN group but increased in the IT group because of the reversal of DN. Conclusions. Our data showed that the level of PTX3 in renal tissue is closely related to renal injury in DN. This may be used to quantify the extent of renal injury in DN, provide a potential early indicator of renal tubular injury in early DN patients, and assess DN clinical progression.

Long pentraxin 3: A novel multifaceted player in cancer

Since its discovery in 1992, long pentraxin 3 (PTX3) has been characterized as soluble patter recognition receptor, a key player of the innate immunity arm with non-redundant functions in pathogen recognition and inflammatory responses. As a component of the extra-cellular matrix milieu, PTX3 has been implicated also in wound healing/tissue remodeling, cardiovascular diseases, fertility, and infectious diseases. Consequently, PTX3 levels in biological fluids have been proposed as a fluid-phase biomarker in different pathological conditions. In the last decade, experimental evidences have shown that PTX3 may exert a significant impact also on different aspects of cancer biology, including tumor onset, angiogenesis, metastatic dissemination and immune-modulation. However, it remains unclear whether PTX3 acts as a good cop or bad cop in cancer. In this review, we will summarize and discuss the scientific literature data focusing on the role of PTX3 in experimental and human tumors, including its putative translational implications.

Inhibitory Role of Pentraxin-3 in Esophageal Squamous Cell Carcinoma

BACKGROUND

Esophageal cancer is the sixth leading cause of cancer-related death worldwide. Pentraxin-3 (PTX3) is a member of the PTX superfamily. Here, we investigated the role of PTX3 in esophageal squamous cell carcinoma (ESCC).

METHODS

The effect of PTX3 on ESCC cell proliferation, colony formation, apoptosis, migration, and invasion was investigated using cell viability assays, colony formation assays, flow cytometry, and migration and invasion assays. The effect of PTX3 on the tumorigenicity of ESCC in vivo was investigated with xenograft studies in nude mice.

RESULTS

PTX3 overexpression in ESCC cells reduced cellular proliferation and colony formation (P < 0.05) and increased the rate of apoptosis (P < 0.05). PTX3 expression had no significant effect on the migratory or invasive potential of ESCC cells. In our mouse model of human ESCC, we achieved 100% successful tumor establishment. Compared with the control and empty vector-expressing groups, the PTX3-expressing group formed significantly smaller tumors (P < 0.05).

CONCLUSIONS

This study indicates that PTX3 might play an inhibitory role in ESCC.

Association of Pentraxin 3 Gene Polymorphisms with Susceptibility to Diabetic Nephropathy

BACKGROUND Diabetic nephropathy (DN) is a major microvascular complication of diabetes. Pentraxin 3 (PTX3) is a member of the acute-phase reactants superfamily and altered plasma levels of PTX3 are associated with DN. We performed a case-control study to analyze the relationship between single nucleotide polymorphisms (SNPs) in PTX3 and the risk for DN in patients with type 2 diabetes. MATERIAL AND METHODS The study included 135 DN patients, 155 non-diabetic nephropathy (NDN) patients, and 152 normal controls (NC) (N=442). We genotyped eight PTX3 SNPs (rs2305619, rs2120243, rs1456099, rs7634847, rs1840680, rs2316706, rs2316709, and rs7616177) using the ABI PRISM SNapshot method. RESULTS The genotype frequencies of rs2305619 and rs2120243 differed significantly between the DN and the NDN groups (p=0.017 and p=0.033, respectively). Patients with the GG variant of rs2305619 showed 4.078-fold higher susceptibility to DN than those with the AA variant (OR=4.078, 95% CI=1.370-12.135, p=0.012); patients with the AA variant of rs2120243 had a lower risk of developing DN (OR=0.213, 95% CI=0.055-0.826, p=0.025). Haplotype analysis showed an association between the CAGGG haplotype in block 1 with DN (p=0.0319). CONCLUSIONS Our findings suggested that PTX3 polymorphisms were associated with an increased risk for DN in Chinese patients with type 2 diabetes.

Tunicamycin-induced Endoplasmic Reticulum Stress Upregulates the Expression of Pentraxin 3 in Human Retinal Pigment Epithelial Cells

PURPOSE

To investigate the production of long pentraxin 3 (PTX3) in response to tunicamycin-induced endoplasmic reticulum (ER) stress and its role in ER stress-associated cell death, PTX3 expression was evaluated in the human retinal pigment epithelial cell line, ARPE-19.

METHODS

PTX3 production in ARPE-19 cells was analyzed in the absence or presence of tunicamycin treatment by enzyme-linked immunosorbent assay. PTX3 protein and mRNA levels were estimated using western blot analysis and real-time reverse transcription-polymerase chain reaction, respectively. Protein and mRNA levels of CCAAT-enhancer-binding protein homologous protein (CHOP) and ARPE-19 cell viability were measured in the presence of tunicamycin-induced ER stress in control or PTX3 small hairpin RNA (shRNA)-transfected ARPE-19 cells.

RESULTS

The protein and mRNA levels of PTX3 were found to be significantly increased by tunicamycin treatment. PTX3 production was significantly decreased in inositol-requiring enzyme 1α shRNA-transfected ARPE-19 cells compared to control shRNA-transfected cells. Furthermore, pretreatment with the NF-κB inhibitor abolished tunicamycin-induced PTX3 production. Decreased cell viability and prolonged protein and mRNA expression of CHOP were observed under tunicamycin-induced ER stress in PTX3 shRNA transfected ARPE-19 cells.

CONCLUSIONS

These results suggest that PTX3 production increased in the presence of tunicamycin-induced ER stress. Therefore, PTX3 could be an important protector of ER stress-induced cell death in human retinal pigment epithelial cells. Inositol-requiring enzyme 1α and the NF-κB signaling pathway may serve as potential targets for regulation of PTX3 expression in the retina. Therefore, their role in PTX3 expression needs to be further investigated.

PTX3, Anti-PTX3, and Anti-C1q Autoantibodies in Lupus Glomerulonephritis

Pentraxin 3 (PTX3) is an acute-phase protein involved in C1q clearance. The presence of anti-C1q and the absence of anti-PTX3 antibodies were associated with lupus glomerulonephritis (LGLN). Our aim was to assess soluble and kidney-expressed PTX3 and their relationships with anti-C1q and anti-PTX3 antibodies in LGLN. Serum PTX3, anti-C1q, anti-dsDNA, and anti-PTX3 antibodies were tested in 130 systemic lupus erythematosus (SLE) patients, 130 healthy and 127 disease controls. Twenty-nine renal biopsies from SLE patients were analyzed and PTX3 immunostaining was quantified by morphometric analysis. Parametric and nonparametric statistics were performed. PTX3 serum levels were lower in SLE versus controls, but they were correlated with proteinuria in LGLN patients (p = 0.001). LGLN patients had higher anti-C1q and lower anti-PTX3 antibody levels than those without (p < 0.0001). LGLN was more prevalent in anti-C1q(+)/anti-PTX3(-) than in anti-C1q(+)/anti-PTX3(+) patients (p < 0.001). No LGLN was observed in anti-C1q(-)/anti-PTX3(+) patients. PTX3 was expressed in glomeruli and renal interstitium. Renal PTX3 was correlated with proteinuria (p = 0.024) and interstitial fibrosis (p = 0.023). PTX3 staining and fibrosis were higher in anti-PTX3(-) than anti-PTX3(+) patients. In conclusion, PTX3 is expressed in glomeruli of LGLN patients, primarily in anti-PTX3(-) patients, where it is correlated with renal fibrosis. Anti-C1q/anti-PTX3 antibody profile seems to be useful in LGLN assessment.

Immunization with pentraxin 3 (PTX3) leads to anti-PTX3 antibody production and delayed lupus-like nephritis in NZB/NZW F1 mice

BACKGROUND

Anti-pentraxin 3 (PTX3) antibodies were associated with the absence of lupus glomerulonephritis in humans.

AIM

To explore the effects of anti-PTX3 antibodies in New Zealand Black/White (NZB/NZW F1) mice and their inherent mechanisms of action.

MATERIALS AND METHODS

30 NZB/NZW F1 mice were subdivided into 3 groups of 10 mice each and subcutaneously injected with PTX3, alum and PBS (group 1), alum and PBS (group 2) or PBS alone (group 3), 3 times 3 weeks apart, before development of renal disease. Mice were followed until natural death. Histological analysis and immunohistochemistry were performed on harvested kidneys. Effects of anti-PTX3 antibodies on C1q binding to immobilized PTX3-anti-PTX3 immune complexes were evaluated in vitro using human SLE sera. Qualitative characterization of human IgG anti-PTX3 was performed.

RESULTS

Only group 1 mice developed anti-PTX3 antibodies. Anti-dsDNA and anti-C1q antibodies appeared significantly later and at lower levels in group 1 mice vs. controls (p < 0.0001). Proteinuria-free and overall survival were significantly increased in group 1 mice vs. controls (p < 0.05 and p = 0.03, respectively). Histopathological analysis showed that glomerular and tubular PTX3 staining and renal lesions were increased in controls compared with immunized mice. Addition of human SLE sera positive for anti-PTX3 antibodies to C1q and fixed PTX3 interfered with C1q binding to PTX3-anti-PTX3 immune complexes. Qualitative characterization of human IgG anti-PTX3 showed an increased proportion of IgG4.

CONCLUSIONS

Anti-PTX3 antibodies delay lupus-like nephritis and prolong survival of NZB/NZW F1 mice. In vitro observations suggest anti-PTX3 antibodies may dampen complement activation via their Fc fragment, likely hindering renal inflammation.

Pentraxin 3 Is Closely Associated With Tubulointerstitial Injury in Lupus Nephritis: A Large Multicenter Cross-Sectional Study

Lupus nephritis always elicits immune inflammatory tissue damages in kidney. Pentraxin 3 (PTX3), mainly produced at inflammatory sites, is known to be involved in the regulation of the innate immunity system. The aim of this study was to investigate the serum and urine levels of PTX3, and the expression of PTX3 in renal tissues in lupus nephritis patients from a large Chinese cohort.The study used cross-sectional survey and 288 active lupus nephritis patients, including discovery cohort and validation cohort, 115 systemic lupus erythematosus (SLE) patients without clinical renal involvement and 46 healthy controls were enrolled. Serum and urine PTX3 were screened by enzyme-linked immunosorbent assay (ELISA). The renal deposition of PTX3 was detected by immunohistochemistry and immunofluorescence.The average level of serum PTX3 in the discovery cohort of lupus nephritis was significantly higher than that in nonrenal involvement SLE group and normal controls (P < 0.001, P < 0.001, respectively), which was confirmed by the validation cohort. Serum PTX3 levels of 15 lupus nephritis patients in remission decreased significantly compared with that in active phase. Serum PTX3 levels were significantly higher in patients with hematuria (P = 0.014), leucocyturia (P = 0.002), acute renal failure (P = 0.001), and nephrotic syndrome (P = 0.036). There were significant correlations between serum PTX3 levels and Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) scores, serum creatinine value, renal pathological activity indices, and serum complement 3 (C3) in active lupus nephritis patients. The urinary PTX3 levels were significantly higher in active lupus nephritis patients compared with patients in remission and normal controls (P = 0.011, P = 0.008, respectively). There were significant associations between urinary PTX3 levels and multiple indices of tubulointerstitial lesions, including urinary KIM-1 (r = 0.368, P = 0.016), neutrophil gelatinase-associated lipocalin (NGAL) (r = 0.320, P = 0.039), microalbumin (r = 0.621, P = 0.003), transferring (r = 0.451, P = 0.040) levels and renal pathological indices scores, especially interstitial inflammation (r = 0.349, P = 0.025) in active lupus nephritis patients. A significant correlation was found between serum and urine PTX3 levels (r = 0.431, P = 0.006). PTX3 staining was mainly observed in tubulointerstitial areas of patients with lupus nephritis, and immunofluorescence study showed that PTX3 could colocalize with fibroblast in interstitium.Circulating and local PTX3 levels were significantly increased in patients with active lupus nephritis and might be a biomarker for the disease progression, especially of tubulointerstitial injury.

Pentraxin-3 Is a TSH-Inducible Protein in Human Fibrocytes and Orbital Fibroblasts

CD34(+) fibrocytes are bone marrow-derived monocyte progenitor cells that traffic to sites of tissue injury and repair. They putatively infiltrate the orbit in thyroid-associated ophthalmopathy where they appear to transition into CD34(+) orbital fibroblasts (OFs) that interact with residential CD34(-) fibroblasts. A unique phenotypic attribute of fibrocytes and CD34(+) OFs is their expression of the functional thyrotropin receptor (TSHR) and other "thyroid-specific" proteins. When activated through TSHR, fibrocytes express a number of cytokines and other inflammatory genes. Here we sought to determine whether pentraxin-3 (PTX-3), an acute-phase protein involved in inflammation and autoimmunity, might be induced by TSH in fibrocytes and OFs. These cells were collected from patients with Graves disease and healthy individuals. PTX-3 mRNA levels were determined by real-time PCR, protein was determined by ELISA and Western blot, and PTX-3 gene promoter activity was assessed with reporter assays. PTX-3 expression was induced by TSH in both cell types, regardless of the health status of the donor and was a consequence of increased steady-state PTX-3 mRNA levels. M22, a TSHR-activating monoclonal antibody, also induced PTX-3. The induction could be attenuated by dexamethasone and by IGF-I receptor-blocking antibodies, teprotumumab and 1H7. TSH effects were mediated through phosphatidylinositol 3-kinase/AKT, mammalian target of rapamycin/p70(s6k), Janus tyrosine kinase 2 pathways, and enhanced PTX-3 mRNA stability. These findings indicate that PTX-3 is a TSH target gene, the expression of which can be induced in fibrocytes and OFs. They suggest that PTX-3 might represent a previously unidentified nexus between the thyroid axis and the mechanisms involved in tissue remodeling.

Could serum pentraxin 3 levels and IgM deposition in skin biopsies predict subsequent renal involvement in children with Henoch-Schönlein purpura?

BACKGROUND

The aim of this study was to evaluate the potential of serum pentraxin 3 (PTX3) values as an early predictor of subsequent renal involvement in patients with Henoch-Schönlein purpura (HSP) with no abnormalities on urinary examination and in renal function tests at disease onset.

METHODS

This was a prospective cohort study which included 60 pediatric patients with HSP (age range 3-15 years) who were diagnosed between February 2011 and October 2012 and 60 age- and sex-matched healthy controls. The patients were followed up for at least 18 months. Clinical findings were recorded for all patients at first examination, and blood samples for routine laboratory parameters and PTX3 value as well as skin biopsy specimens were obtained from each subject.

RESULTS

Of the 60 patients with HSP, 29 (48.3 %) developed subsequent renal involvement, of whom four underwent kidney biopsy. The mean serum PTX3 level of patients with subsequent renal involvement was significantly higher than those of patients without renal involvement and of the controls (2.20 ± 1.30 vs. 1.36 ± 0.85 and 1.03 ± 0.7 ng/ml, respectively; p = 0.004). Immunofluorescence evaluation of skin biopsy revealed that in addition to immunoglobulin A (IgA) deposition, the IgM deposition was significantly associated with subsequent renal involvement (p = 0.008).

CONCLUSIONS

A high PTX3 level and IgM staining in skin biopsies from HSP patients may be harbingers of subsequent renal involvement.

Advances in our understanding of the pathogenesis of Henoch-Schönlein purpura and the implications for improving its diagnosis

Henoch-Schönlein purpura (HSP) is a leukocytoclastic vasculitis classically characterized by palpable purpura, arthritis, abdominal pain and renal disease. In this article, we summarize our current understanding of the pathogenesis of HSP and the implications for improving its diagnosis. Although the pathogenesis of HSP is not fully understood yet, exciting new information has emerged in recent years, leading to a better understanding of its pathogenesis. Here, we discuss genetic predisposition, immunoglobulins with a particular emphasis on IgA1, activated complements, cytokines and chemokines, abnormal coagulation and autoantibodies in the underlying pathogenic mechanisms. Finally, diagnostic criteria for HSP developed by institutions such as the American College of Rheumatology and the European League against Rheumatism/Paediatric Rheumatology European Society were proposed to improve early detection and diagnosis.

Pentraxin 3 as a novel early biomarker for the prediction of Henoch-Schönlein purpura nephritis in children

We investigated the potential role of pentraxin 3 (PTX3) in Henoch-Schönlein purpura (HSP), a common multisystemic vasculitis affecting children, as a predictor of Henoch-Schönlein purpura nephritis (HSPN). A total of 108 cases consisting of 34 children with HSP, 37 children with HSPN, and 37 healthy control children were enrolled in this prospective study from March 2010 to February 2013. Blood and urine samples were collected to measure plasma PTX3, C-reactive protein (CRP), serum creatinine, blood urea nitrogen (BUN), urine microalbumin (MALB), and β2-microglobulin (β2-MG). Median plasma PTX3 concentrations were significantly higher in children with HSPN and HSP than in control subjects before treatment (6.99, 4.18-9.78 ng/ml; 3.19, 1.13-4.27 ng/ml; 1.24, 0.87-2.08 ng/ml, respectively; all p < 0.05). Median plasma PTX3 concentrations were also significantly higher in children with HSPN than in children with HSP before treatment (6.99, 4.18-9.78 vs. 3.19, 1.13-4.27 ng/ml; p < 0.05). After treatment, median plasma PTX3 concentrations significantly decreased in children with HSP (from 3.19, 1.13-4.27 to 1.08, 0.65-2.19 ng/ml; p < 0.05) and HSPN (from 6.99, 4.18-9.78 to 1.29, 1.01-2.26 ng/ml; p < 0.05). Plasma PTX3 concentration was positively correlated with CRP (rho = 0.532, p = 0.001), MALB (rho = 0.606, p < 0.001), β2-MG (rho = 0.490, p = 0.002), and 24-h urinary protein quantity (rho = 0.650, p < 0.001) in children with HSPN. Considering vasculitis, we found that PTX3 could be used as a more efficient potential predictor of HSPN than CRP as indicated by the area under the receiver operating characteristic (ROC) curve (AUCROC) of PTX3 (AUCROC = 0.837; p < 0.001) and CRP (AUCROC = 0.514; p = 0.845). The threshold PTX3 concentration with optimal sensitivity and specificity was 4.30 ng/ml (sensitivity 73.0 %, specificity 79.6 %).

CONCLUSION

PTX3 seems to have an important role in multisystemic vasculitis of HSP, may be involved in the development of HSPN, and used as an early biomarker to predict HSPN.

Pentraxin 3 is a marker of early joint inflammation in patients with juvenile idiopathic arthritis

Pentraxin 3 (PTX3) is an acute phase protein produced in different body tissues. The aims of this study were to characterize PTX3 secretion in synovial fluid (SF) of juvenile idiopathic arthritis (JIA) patients and to analyze the correlation of PTX3 levels in SF with clinical characteristics and the course of the disease. SF-PTX3 levels were measured in a cohort of 75 consecutive JIA patients followed in a single center. Patients' clinical characteristics, disease course, and therapies were analyzed for their correlation with SF-PTX3 levels. A synovial cell line was used to study the kinetics of PTX3 secretion by synoviocytes. SF-PTX3 levels varied over a wide range. Elevated SF-PTX3 levels were detected in patients who subsequently required treatment with disease-modifying antirheumatic drugs during the follow-up period. SF-PTX3 levels were found to be inversely correlated with the length of time from onset of joint swelling. No correlation was found between synovial and serum PTX3 or C-reactive protein (CRP). Following in vitro stimulation of synovial cell line with TNFa or IL1, the secretion of PTX3 increases transiently in the first 48-72 h. A similar increase was obtained in patients' synovial fluids but not with IL6. Higher SF-PTX3 levels were found when tested closer to arthritis exacerbation and 48-72 h after in vitro stimulation of cells from a synovial cell line, implying that PTX3 plays a role in early stages of inflammation. Higher SF-PTX3 levels were associated with several clinical features reflecting disease severity and prognostic data. Measuring SF-PTX3 levels may help in providing a more focused and patient-adjusted treatment.

Immunopathology of lupus nephritis

When patients with systemic lupus erythematosus (SLE) present with urinary abnormalities, a renal biopsy is usually needed to rule out or confirm lupus nephritis. Renal biopsy is also needed to define the type of renal manifestation as different entities are associated with different outcomes; hence, renal biopsy results shape lupus management. But why does lupus nephritis come in different shapes? Why do patients with SLE often show change over time in class of lupus nephritis or have mixed forms? How does autoimmunity in SLE evolve? Why does loss of tolerance against nuclear antigens preferentially affect the kidney? Why are immune complex deposits in different glomerular compartments associated with different outcomes? What determines crescent formation in lupus? In this review, we discuss these questions by linking the latest information on lupus pathogenesis into the context of the different classes of lupus nephritis. This should help the basic scientist, the pathologist, and the clinician to gain a more conceptual view on the immunopathology of lupus nephritis.

The pathogenesis of lupus nephritis

Lupus nephritis is an immune complex GN that develops as a frequent complication of SLE. The pathogenesis of lupus nephritis involves a variety of pathogenic mechanisms. The extrarenal etiology of systemic lupus is based on multiple combinations of genetic variants that compromise those mechanisms normally assuring immune tolerance to nuclear autoantigens. This loss of tolerance becomes clinically detectable by the presence of antinuclear antibodies. In addition, nucleic acids released from netting or apoptotic neutrophils activate innate and adaptive immunity via viral nucleic acid-specific Toll-like receptors. Therefore, many clinical manifestations of systemic lupus resemble those of viral infection. In lupus, endogenous nuclear particles trigger IFN-α signaling just like viral particles during viral infection. As such, dendritic cells, T helper cells, B cells, and plasma cells all contribute to the aberrant polyclonal autoimmunity. The intrarenal etiology of lupus nephritis involves antibody binding to multiple intrarenal autoantigens rather than the deposition of circulating immune complexes. Tertiary lymphoid tissue formation and local antibody production add to intrarenal complement activation as renal immunopathology progresses. Here we provide an update on the pathogenic mechanisms that lead to lupus nephritis and provide the rationale for the latest and novel treatment strategies.

Urinary C reactive protein levels in dogs with leishmaniasis at different stages of renal damage

The objectives of the study were to validate a time-resolved immunofluorometric assay for C reactive protein (CRP) quantification in urine of dogs and to investigate the influence that the presence of proteinuria and azotemia could have on serum and urinary CRP (uCRP) values in dogs with leishmaniasis. Samples obtained from dogs naturally infected with Leishmania infantum were classified into four groups on the basis of the results of urinary protein/creatinine ratio and serum creatinine (sCr). In addition, 7 dogs were monitored at initial diagnosis and after a follow up visit. The assay showed good analytical performance based on precision, accuracy and limit of detection results. Results of the study suggested that CRP is present in urine of dogs with leishmaniasis and renal damage since uCRP/creatinine ratio was significantly increased in dogs with proteinuria, being the highest values observed in dogs with proteinuria and elevated sCr, and that the measurement of uCRP could be a tool to detect and evaluate the possible kidney damage associated with this disease.

Elevated circulating levels and tissue expression of pentraxin 3 in uremia: a reflection of endothelial dysfunction

Elevated systemic pentraxin 3 (PTX3) levels appear to be a powerful marker of inflammatory status and a superior outcome predictor in patients with chronic kidney disease (CKD). As previous data imply that PTX3 is involved in vascular pathology and that adipose tissue mass may influence circulating PTX3 levels, we aimed to study the importance of adipose tissue expression of PTX3 in the uremic milieu and its relation to endothelial dysfunction parameters. Plasma PTX3 and abdominal subcutaneous adipose tissue (SAT) PTX3 mRNA levels were quantified in 56 stage 5 CKD patients (median age 57 [range 25-75] years, 30 males) and 40 age and gender matched controls (median age 58 [range 20-79] years, 27 males). Associations between PTX3 measures and an extensive panel of clinical parameters, including surrogate markers of endothelial function, were assessed. Functional ex vivo studies on endothelial status and immunohistochemical staining for PTX3 were conducted in resistance subcutaneous arteries isolated from SAT. SAT PTX3 mRNA expression correlated with plasma PTX3 concentrations (rho = 0.54, p = 0.0001) and was increased (3.7 [0.4-70.3] vs. 1.2 [0.2-49.3] RQ, p = 0.02) in CKD patients with cardiovascular disease (CVD), but was not significantly different between patients and controls. The association to CVD was lost after adjustments. SAT PTX3 mRNA levels were independently correlated to asymmetric dimethylarginine and basal resistance artery tone developed after inhibition with nitric oxide synthase and cyclooxygenase (rho = -0.58, p = 0.002). Apparent positive PTX3 immunoreactivity was observed in both patient and control arteries. In conclusion, fat PTX3 mRNA levels are associated with measures of endothelial cell function in patients with CKD. PTX3 may be involved in adipose tissue-orchestrated mechanisms that are restricted to the uremic milieu and modify inflammation and vascular complications in CKD patients.

Pentraxins in nephrology: C-reactive protein, serum amyloid P and pentraxin-3

Every clinician uses C-reactive protein (CRP) levels as a biomarker for systemic inflammation in acute disorders. Nephrologists also consider CRP levels as a predictor for overall mortality in patients with chronic kidney disease or end-stage renal disease. But what is the biological function of CRP? CRP is a member of the family of pentraxins, which are small pentameric innate immunity effector proteins. Pentraxins are absent or weakly expressed during homeostasis. However, the pro-inflammatory cytokines interleukin (IL)-1, IL-6 and tumour necrosis factor induce CRP and serum amyloid P (SAP) in hepatocytes, whereas the long pentraxins, such as pentraxin (PTX)-3, are produced in peripheral tissues and monocytic phagocytes. Pentraxins opsonize pathogens or other particles such as dead cells, for their phagocytic clearance or induce pathogen killing in extracellular compartments. In this review, we discuss the immunoregulatory properties of the different members of the pentraxin family. We discuss the evolving evidence demonstrating their roles in acute and chronic forms of kidney disease and the significance of SAP and PTX3 as additional biomarkers of innate immune activation and systemic inflammation.

Pentraxin 3, a sensitive early marker of hemodialysis-induced inflammation

BACKGROUND/AIMS

The purpose of this investigation was to determine if the long pentraxin 3 (PTX-3) may be a useful marker of intradialytic inflammation since it is rapidly released in the vasculature.

METHODS

PTX-3, interleukin-6, tumor necrosis factor-α and C-reactive protein were measured before and during a hemodialysis session in 22 patients and compared with healthy subjects. The effect of dialysis with low-flux, high-flux membranes and hemodiafiltration on the inflammatory response was compared in 11 patients.

RESULTS

C-reactive protein and interleukin-6 levels did not change, while a modest decrease in tumor necrosis factor-α was observed during hemodialysis. The plasma PTX-3 concentration was significantly increased (p < 0.001) after 60 min and peaked at 180 min during hemodialysis. There was no difference in the intradialytic increase in PTX-3 using different dialysis membranes and modalities.

CONCLUSION

PTX-3 stands out as a rapid and sensitive marker of hemodialysis-induced inflammation. Membrane flux and hemodiafiltration did not alter the inflammatory response.

Long pentraxin 3 (PTX3) in the light of its structure, mechanism of action and clinical implications

Pentraxins are a group of evolutionarily conserved ancient proteins. Depending on their structure, pentraxins are divided into short and long pentraxin families. Pentraxin 3 (PTX3) is the prototype of the long pentraxin group. PTX3 synthesis is stimulated by a variety of molecules involved in the inflammatory process. The inflammatory mediator is typically produced at inflammatory sites; however, it can also be released at the sites remote from the original inflammatory insult. Although mainly expressed by vascular endothelium and smooth muscle cells, PTX3 is also synthesized by myeloid dendritic cells, mononuclear macrophages/phagocytes, vascular endothelial and smooth muscle cells, fibroblasts, adipocytes, cumulus oophorus cells mesangial cells, synovial cells and chondrocytes. PTX3 binds to several ligands including complement component C1q, factor H, ficolin-1 (M-ficolin), mannose-binding lectin, fibroblast growth factor 2, P-selectin, matrix protein TSG6 and Klebsiella pneumoniae; it is also known to play a role in humoral innate immunity as well as in degenerated and apoptotic cells clearance. PTX3 acts as a modulator of inflammatory processes, modifies angiogenesis and atherosclerotic lesion development, and participates in extracellular matrix formation. Due to the fact of PTX3 being primarily produced and released by vascular wall cells, it might be used as a sensitive and independent inflammatory marker.

C-reactive protein concentrations in serum of dogs with naturally occurring renal disease

The current study was undertaken to investigate the relation between serum C-reactive protein (CRP) concentrations and parameters of renal function in dogs with naturally occurring renal disease. Dogs were assigned to groups according to plasma creatinine concentration, urinary protein-to-creatinine ratio (UP/UC), and exogenous plasma creatinine clearance (P-ClCr) rates. Group A (healthy control dogs; n = 8): non-azotemic (plasma creatinine <125 µmol/l) and nonproteinuric (UP/UC <0.2), with P-ClCr rates >90 ml/min/m2; group B (n = 11): non-azotemic, nonproteinuric dogs with reduced P-ClCr rates (50–89 ml/min/m2); group C (n = 7): azotemic, borderline proteinuric dogs (P-ClCr rates: 22–67 ml/min/m2); and group D (n = 6): uremic, proteinuric dogs (not tested for P-ClCr). The serum CRP concentrations were measured via commercial enzyme-linked immunosorbent assay. The CRP concentrations in the clinically healthy dogs (group A) ranged from 2.09 mg/l to 8.60 mg/l (median: 3.21 mg/l). In comparison with dogs of group A, median CRP concentrations were significantly ( P < 0.01) elevated in dogs of group B (17.6 mg/l, range: 17.0–19.2 mg/l), group C (24.8 mg/l, range: 18.0–32.5 mg/l), and group D (59.7 mg/l, range: 17.7–123 mg/l). Serum CRP was significantly related to P-ClCr ( r = –0.83; P < 0.001), plasma creatinine ( r = 0.81; P < 0.001), UP/UC ( r = 0.70; P < 0.001), and leukocytes ( r = 0.49; P < 0.01). The significant relations between serum CRP concentrations and biochemical parameters of kidney function in plasma and urine suggest that a stimulation of the acute phase response is implicated in the pathogenesis of canine renal disease.

Protective molecules and their cognate antibodies: new players in autoimmunity

Impairment of the clearance of apoptotic material seems to contribute to autoantigen exposure, which can initiate or maintain an autoimmune response in predisposed individuals. Complement component C1q, Creactive protein (CRP), serum amyloid P (SAP), mannose-binding lectin (MBL), apolipoprotein A-1 (Apo A-1) and long pentraxin 3 (PTX3) are molecules involved in the removal of apoptotic bodies and pathogens, and in other antiinflammatory pathways. For this reason they have been called "protective" molecules. C1q has a key role in the activation of the complement cascade and acts as a bridging molecule between apoptotic bodies and macrophages favouring phagocytosis. In addition to other functions, CRP, SAP and MBL bind to the surface of numerous pathogens as well as cellular debris and activate the complement cascade, thus stimulating their clearance by immune cells. The role of PTX3 is more controversial. In fact, PTX also promotes the clearance of microorganisms, but the activation of the complement cascade through C1q and removal of apoptotic material can be either stimulated or inhibited by this molecule. Antibodies against protective molecules have been recently reported in systemic lupus erythematosus and other autoimmune rheumatic diseases. Some of them seem to be pathogenetic and others protective. Thus, protective molecules and their cognate antibodies may constitute a regulatory network involved in autoimmunity. Dysregulation of this system might contribute to the development of autoimmune diseases in predisposed individuals.

Pathogenesis of Henoch-Schönlein purpura nephritis

The severity of renal involvement is the major factor determining the long-term outcome of children with Henoch-Schönlein purpura (HSP) nephritis (HSPN). Approximately 40% children with HSP develop nephritis, usually within 4 to 6 weeks after the initial onset of the typical purpuric rashes. Although the pathogenetic mechanisms are still not fully delineated, several studies suggest that galactose-deficient IgA1 (Gd-IgA1) is recognized by anti-glycan antibodies, leading to the formation of the circulating immune complexes and their mesangial deposition that induce renal injury in HSPN.

Binding of the long pentraxin PTX3 to factor H: interacting domains and function in the regulation of complement activation

The long pentraxin PTX3 is a multifunctional soluble molecule involved in inflammation and innate immunity. As an acute phase protein, PTX3 binds to the classical pathway complement protein C1q, limits tissue damage in inflammatory conditions by regulating apoptotic cell clearance, and plays a role in the phagocytosis of selected pathogens. This study was designed to investigate the interaction of PTX3 with factor H (FH), the main soluble alternative pathway regulatory protein. We report that PTX3 binds FH with an apparent K(d) of 1.1 x 10(-7) M, and define two binding sites for PTX3 on FH. The primary binding site is located on FH domains 19-20, which interact with the N-terminal domain of PTX3, while a secondary binding site on domain 7 binds the glycosylated PTX3 pentraxin domain. The FH Y402H polymorphism, which affects binding to the short pentraxin CRP, did not affect binding to PTX3. Surface-bound PTX3 enhances FH recruitment and iC3b deposition and PTX3-bound FH retains its activity as a cofactor for factor I-mediated C3b cleavage. Thus, our findings identify PTX3 as a unique FH ligand in that it can bind both of the two hot-spots of FH, namely SCR7 and SCR19-20 and indicate that PTX3 participates in the localization of functionally active FH.

The long pentraxin 3 and its role in autoimmunity

OBJECTIVES

To review the physiological and physiopathological roles of pentraxin 3 (PTX3), focusing on autoimmunity and vascular pathology.

METHODS

A systematic literature review using the keywords "pentraxin 3," "innate immunity," "apoptosis," "autoimmunity," and "endothelial dysfunction" from 1990 to 2007 was performed. All relevant articles and pertinent secondary references in English were reviewed.

RESULTS

PTX3 has a large number of multiple functions in different contexts. PTX3 plays an important role in innate immunity, inflammation, vascular integrity, fertility, pregnancy, and also in the central nervous system. In innate immunity, its normal function is to increase the immune response to selected pathogens while also exerting control over potential autoimmune reactions. It maintains a tightly homeostatic equilibrium in the local immune microenvironment by avoiding an exaggerated immune response and controlling peripheral tolerance to self-antigens. In contrast, in some autoimmune diseases, PTX3 appears to be involved in the development of autoimmune phenomena. A possible explanation for these apparent paradoxical functions may be related to the highly polymorphic PTX3 gene.

CONCLUSION

PTX3 is physiologically a protective molecule. However, in several autoimmune diseases PTX3 appears to facilitate the development of autoimmunity. The PTX3 gene could influence the development of autoimmune reactions and vascular involvement in human pathology.

Role of the soluble pattern recognition receptor PTX3 in vascular biology

Pentraxins act as soluble pattern recognition receptors with a wide range of functions in various pathophysiological conditions. The long-pentraxin PTX3 shares the C-terminal pentraxin-domain with short-pentraxins C-reactive protein and serum amyloid P component and possesses an unique N-terminal domain. These structural features suggest that PTX3 may have both overlapping and distinct biological/ligand recognition properties when compared to short-pentraxins. PTX3 serves as a mechanism of amplification of inflammation and innate immunity. Indeed, vessel wall elements produce high amounts of PTX3 during inflammation and the levels of circulating PTX3 increase in several pathological conditions affecting the cardiovascular system. PTX3 exists as a free or extracellular matrix-associated molecule and it binds the complement fraction C1q. PTX3 binds also apoptotic cells and selected pathogens, playing a role in innate immunity processes. In endothelial cells and macrophages, PTX3 upregulates tissue factor expression, suggesting its action as a regulator of endothelium during thrombogenesis and ischaemic vascular disease. Finally, PTX3 binds the angiogenic fibroblast growth factor-2, thus inhibiting its biological activity. Taken together, these properties point to a role for PTX3 during vascular damage, angiogenesis, atherosclerosis, and restenosis.

Plasma pentraxin 3 in patients with chronic kidney disease: associations with renal function, protein-energy wasting, cardiovascular disease, and mortality

BACKGROUND AND OBJECTIVES

Plasma protein pentraxin 3 concentrations are elevated in a wide range of diseased states. However, no study has evaluated protein pentraxin 3 in patients with chronic kidney disease.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Plasma protein pentraxin 3 concentrations were analyzed in relation to GFR, inflammation, cardiovascular disease, and protein-energy wasting in 71 patients with stages 3 to 4 chronic kidney disease, 276 patients with stage 5 chronic kidney disease, and 61 control subjects. Survival (5 yr) in patients with stage 5 chronic kidney disease was analyzed in relation to protein pentraxin 3 levels.

RESULTS

Both patient groups with chronic kidney disease had higher protein pentraxin 3 concentrations than control subjects, with the highest concentration in patients with stage 5 chronic kidney disease. In all patients with chronic kidney disease, protein pentraxin 3 correlated negatively with GFR and positively with inflammatory markers. Patients with protein-energy wasting, inflammation, and cardiovascular disease had higher concentrations of protein pentraxin 3 than their counterparts. Patients with high protein pentraxin 3 levels had higher all-cause and cardiovascular mortality. After adjustment for age, gender, C-reactive protein, and cardiovascular disease, all-cause mortality was still significantly higher in patients with high protein pentraxin 3. Finally, protein pentraxin 3 showed a predictive value of mortality similar to that of IL-6 and better than C-reactive protein.

CONCLUSION

Plasma protein pentraxin 3 increases as GFR declines and is associated with the presence of cardiovascular disease and protein-energy wasting. Furthermore, in patients with chronic kidney disease, elevated protein pentraxin 3 predicted all-cause mortality.

[The role of long pentraxin 3, a new inflammatory mediator in inflammatory responses]

Pentraxin 3 (PTX3) is suggested to play important roles in the innate resistance against pathogens, regulation of inflammatory reactions, and clearance of apoptotic cells. PTX3 is the first long pentraxin identified. Long pentraxin shares a C-terminal pentraxin domain with the classical short pentraxin (C-reactive protein, serum amyloid P), but holds an unrelated N-terminal domain that is unique to the long pentraxin. While the short pentraxin is produced only in the liver, PTX3 is made by diverse types of cells, prominently endothelial cells and macrophage, in response to inflammatory signals. Unlike the short pentraxin, the expression of PTX3 in multiple types of tissue cells implies a mechanism for local amplification of innate resistance at the site of infection and inflammation. PTX3 plasma levels are very low in normal subjects but are rapidly increased by inflammatory conditions resulting from a wide range of diseased states, from infection to autoimmune and degenerative disorders. Critically ill patients show elevated circulating levels of PTX3 which are determined by the severity of the disease. Clinical evidence has demonstrated that the elevated PTX3 levels might be a useful early and sensitive marker for severely ill patients. Further studies will definitely be needed to deepen our understanding of PTX3.

Nitric oxide and superoxide in rat mesangial cells: modulation by C-reactive protein

BACKGROUND

C-reactive protein (CRP) has been linked to cardiovascular and renal disease. We evaluated the effects of CRP on the production of nitric oxide (NO) and superoxide by rat mesangial cells (RMC) and the impact on cell function.

METHODS AND RESULTS

RMC were incubated with cytokines (IFN-gamma, IL-1beta, and LPS) and CRP (10-100 microg/ml) for 24-72 h. Exposure to CRP resulted in a time- and dose-dependent reduction in NO accumulation (p<0.05). Although inducible nitric oxide synthase (iNOS) protein expression was unaltered after 48 h, CRP stimulated expression of HSP90. Steady state abundance of iNOS mRNA increased nearly threefold after a 24-h exposure to CRP. Incubation with 100 microg/ml CRP for 60-120 min resulted in a 272% increase in superoxide production that was prevented by diphenyleneiodium chloride but not L-NAME (p<0.0001).

CONCLUSION

CRP enhances superoxide release in RMC, which in turn inactivates NO and reduces net production. The functional relevance of these CRP-induced changes is supported by increased expression of HSP90 in RMC exposed to the mediator. These findings suggest that systemic inflammation, which contributes to the pathogenesis of atherosclerosis, may play a role in the progression of kidney disease.

TNFalpha-induced long pentraxin PTX3 expression in human lung epithelial cells via JNK

Long pentraxin 3 (PTX3), an acute-phase protein, is a newly clarified mediator for innate immunity and inflammation. As a soluble pattern recognition receptor, it has a nonredundant role in antifungal infection. Overexpression of PTX3 worsens acute lung injury. The lung epithelium is a critical factor in defense against pulmonary pathogens; it is also involved in acute inflammatory responses related to tissue injury. However, very little is known about how PTX3 is regulated in the lung epithelium. In this study, we found that i.v. injection of LPS induced PTX3 expression in rat lung alveolar epithelium. Using human lung cell lines and primary epithelial cells, we found that PTX3 expression was significantly up-regulated by TNF-alpha in a time- and dose-dependent manner, but not by LPS. Pretreatment with either actinomycin D or cycloheximide abolished TNF-alpha-induced PTX3 expression, indicating the requirement for both transcriptional and translational regulation. The TNF-alpha-induced PTX3 expression was blocked by SP600125, a JNK-specific inhibitor, but not by the inhibitors against NF-kappaB, ERKs, or p38 MAPK. Knockdown of either JNK1 or JNK2 with small interfering RNA also significantly reduced the regulated PTX3 expression. Thus, lung epithelial cells appear to be a major local source for PTX3 production, which could be induced in vivo from these cells by LPS or other inflammatory stimuli, and may be an important mediator for host defense and tissue damage. The importance of the JNK pathway for the regulated PTX3 expression may be a potential target for its regulation in the lung.

Protective Molecules–C-Reactive Protein (CRP), Serum Amyloid P (SAP), Pentraxin3 (PTX3), Mannose-Binding Lectin (MBL), and Apolipoprotein A1 (Apo A1), and Their Autoantibodies: Prevalence and Clinical Significance in Autoimmunity

Apoptotic defects and impaired clearance of cellular debris are considered key events in the development of autoimmunity, as they can contribute to autoantigen overload, and may initiate an autoimmune response. The pentraxins are a group of highly conserved proteins including the short pentraxins, C-reactive protein (CRP) and serum amyloid-P (SAP), and the long pentraxin-3 (PTX3), which are all involved in innate immunity and in acute-phase responses. Mannan-binding lectin (MBL) is an activator of the complement system, and Apolipoprotein A-1 (Apo A-1) is pivotal in the cholesterol homeostasis and has anti-inflammatory properties. In addition to their role in innate immunity and inflammation, each of these five proteins participates in the removal of damaged and apoptotic cells. In this review, we discuss the clinical significance of different levels of these proteins, their role in the induction or protection from autoimmunity, and the presence of specific autoantibodies against them in the different autoimmune diseases.

Human renal epithelial cells produce the long pentraxin PTX3

BACKGROUND

Pentraxin 3 (PTX3) is a prototypic long pentraxin with structural similarities in the C-terminal domain to the classical short pentraxins C-reactive protein (CRP) and serum amyloid P component. PTX3 is suggested to play an important role in the innate resistance against pathogens, regulation of inflammatory reactions, and clearance of apoptotic cells. Unlike the classic pentraxins, PTX3 is mainly expressed extrahepatically. The present study was designed to investigate the expression of PTX3 by human proximal renal tubular epithelial cells (PTECs).

METHODS

PTECs were cultured in the presence or absence of inflammatory cytokines. PTX3 mRNA expression was measured by reverse transcription-polymerase chain reaction (RT-PCR) in human kidney and PTECs. PTX3 protein levels in PTEC cultures were quantified by enzyme-linked immunosorbent assay (ELISA).

RESULTS

PTX3 mRNA was shown to be constitutively expressed in human kidney. Constitutive expression and production of PTX3 was shown in primary mesangial cells, in primary PTECs, and in renal fibroblasts. Further analysis showed that interleukin (IL)-1 and tumor necrosis factor-alpha (TNF-alpha) stimulation strongly enhanced the expression and production of PTX3 in PTECs in a dose- and time-dependent manner. In addition, activation of PTECs with IL-17 and CD40L, respectively, but not with IL-6 or IL-4, resulted in strongly increased production of PTX3, whereas granulocyte macrophage-colony-stimulating factor (GM-CSF) inhibited IL-1-induced PTX3 production. PTX3 produced by PTEC is functionally active in binding C1q.

CONCLUSION

These results indicate that PTX3 is expressed and released by PTECs and that in proinflammatory conditions PTX3 production is up-regulated. Local expression of PTX3 may play a role in the innate immune response and inflammatory reactions in the kidney.