Multiple drug-resistant gene 1 in children with steroid-sensitive nephrotic syndrome

Assessment of the Link of ABCB1 and NR3C1 gene polymorphisms with the prednisolone resistance in pediatric nephrotic syndrome patients of Bangladesh: A genotype and haplotype approach

Introduction

Nephrotic syndrome is a common pediatric kidney disease. Investigations on several genetic polymorphisms revealed an inconsistent influence on the resistance of patients to steroids.

Objectives

This study aimed to identify the association of ABCB1 (1236C > T, 2677G > T, 3435C > T), NR3C1 (rs10482634, rs6877893), and CYP3A5 (CYP3A5*3) gene polymorphism as well as sociodemographic and clinicopathological parameters with the risk of developing prednisolone resistance in pediatric patients with nephrotic syndrome.

Methods

A case-control analysis was performed on 180 nephrotic syndrome patients. Among them, 30 patients were classified as prednisolone resistant group, and 150 were classified as prednisolone sensitive group. Genotyping was performed by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method.

Results

No significant association of 1236C > T polymorphism with the risk of prednisolone resistance (p > 0.05) was found. The GT heterozygous of 2677G > T was found to be significantly associated with the development of prednisolone resistance (OR = 3.9, p = 0.034). In the case of 3435C > T, a statistically significant association was observed in TC heterozygous and TT mutant homozygous genotypes (OR = 0.38, p = 0.047; OR = 3.06, p = 0.038, respectively) with prednisolone resistance. For rs10482634 polymorphism, the AG heterozygous and AG+GG genotypes were significantly linked with prednisolone resistance (OR = 2.40, p = 0.033; OR = 2.36, p = 0.034, respectively). We found no association with the risk of prednisolone resistance with rs6877893 and CYP3A5*3 polymorphism (p > 0.05). CTC and TGT haplotypes of ABCB1 and GA haplotype of NR3C1 were also associated with the increased risk of pediatric prednisolone resistance (OR = 4.47, p = 0.0003; OR = 2.71, p = 0.03; and OR = 4.22, p = 0.022, consecutively). We also observed the correlation of different sociodemographic and clinicopathological factors with prednisolone resistance in pediatric nephrotic syndrome.

Conclusion

Our findings showed a significant association of ABCB1 and NR3C1 gene polymorphisms with prednisolone resistant pediatric nephrotic syndrome.

Overexpression of P-glycoprotein and MRP-1 are pharmacogenomic biomarkers to determine steroid resistant phenotype in childhood idiopathic nephrotic syndrome

Steroid remains the keystone therapy for Idiopathic Nephrotic Syndrome (NS). Besides genetic factors and histological changes, pharmacogenomic factors also affect the steroid response. The upregulation of P-glycoprotein (P-gp) and Multidrug resistance-associated protein 1 (MRP-1) modulate the pharmacokinetics of steroids and may contribute to steroid resistance. Flow-cytometric analysis of P-gp, MRP-1 expression and functional activity on peripheral blood mononuclear cells (PBMCs) was carried out in steroid-sensitive nephrotic syndrome (SSNS) (n = 171, male 103, mean age = 8.54 ± 4.3); and steroid-resistant nephrotic syndrome (SRNS) (n = 83, male 43, mean age = 7.43 ± 4.6) patients. The genotypings of MDR-1 gene were carried out using PCR-RFLP. We observed that the percentage expression of P-gp (10.01 ± 2.09 and 3.79 ± 1.13, p < 0.001); and MRP-1 (15.91 ± 3.99 and 7.40 ± 2.33, p < 0.001) on lymphocyte gated population were significantly higher in SRNS than that of SSNS. The functional activity of P-gp and MRP-1 was also significantly escalated in SRNS as compared to SSNS (68.10 ± 13.35 and 28.93 ± 7.57, p < 0.001); (72.13 ± 8.34 and 31.56 ± 8.65, p < 0.001) respectively. AUC-ROC curve analysis revealed that P-gp and MRP-1 expression with a cut-off value of 7.13% and 9.62% predicted SRNS with the sensitivity of 90% and 80.7%; and specificity 90% and 80%, respectively. Moreover, MDR-1 homozygous mutant TT+AA for G2677T/A (rs2032582) was significantly associated with SRNS (p = 0.025, OR = 2.86 CI = 1.14-7.14). The expression of P-gp (9.68 ± 4.99 v/s 5.88 ± 3.38, p = 0.002) was significantly higher in the patients of homozygous mutant alleles compared to wildtype GG. The increased expression and functionality of P-gp and MRP-1 contribute to steroid resistance, and MDR-1 homozygous mutant G2677T/A promotes steroid resistance by inducing P-gp expression in NS.

Reciprocal Relationship Between HDAC2 and P-Glycoprotein/MRP-1 and Their Role in Steroid Resistance in Childhood Nephrotic Syndrome

Background: Reduced HDACs levels have been reported in steroid resistant chronic obstructive pulmonary disease and bronchial asthma patients. P-glycoprotein (P-gp) over expression in peripheral blood mononuclear cells (PBMCs) has been reported in patients with steroid resistant nephrotic syndrome (NS). Whether and how HDACs and P-gp are linked with each other is not clear, especially in NS patients. Aim: To evaluate mRNA expression of P-gp/MRP-1 and HDAC2 in PBMCs of steroid sensitive (SSNS) and steroid resistant nephrotic syndrome (SRNS) patients, and determine the relationship between expression of HDAC2 and P-gp/ MRP-1in NS patients. Methods: Twenty subjects (10 in each group), SSNS (mean age 7.54 ± 3.5 years), and SRNS (mean age 8.43 ± 3.8 years) were recruited. mRNA expression of HDAC2 and P-gp/MRP-1 was studied by quantitative real time PCR. PBMCs were treated with Theophylline, 1 μM, and Trichostatin A, 0.8 μM, for 48 h for induction and suppression of HDAC2, respectively. Results: At baseline, expression of P-gp (4.79 ± 0.10 vs. 2.13 ± 0.12, p < 0.0001) and MRP-1 (3.99 ± 0.08 vs. 1.99 ±0.11, p < 0.0001) on PBMCs were increased whereas, HDAC2 mRNA levels (2.97 ± 0.15 vs. 6.02 ± 0.13, p < 0.0001) were significantly decreased in SRNS as compared to that of SSNS patients. Compared to baseline, theophylline reduced mRNA expression of P-gp and MRP-1 (fold change 2.65 and 2.21, ^* p < 0.0001 in SRNS) (fold change 1.25, 1.24, ^* p < 0.0001 in SSNS), respectively. However, it increased the expression of HDAC2 (fold change 5.67, ^* p < 0.0001 in SRNS) (fold change 6.93, ^* p < 0.0001 in SSNS). Compared to baseline, TSA treatment increased mRNA levels of P-gp and MRP-1 (fold change 7.51, 7.31, ^* p < 0.0001 in SRNS) and (fold change 3.49, 3.35, ^* p < 0.0001 in SSNS), respectively. It significantly decreased the level of HDAC2 (fold change 1.50, ^* p < 0.0001 in SRNS) (fold change 2.53, ^* p < 0.0001 in SSNS) patients. Conclusion: Reduced HDAC2 and increased P-gp/MRP-1 activity may play a role in response to steroids in childhood NS. HDAC2 and P-gp/MRP-1 are in reciprocal relationship with each other.

A PRISMA-compliant meta-analysis of MDR1 polymorphisms and idiopathic nephrotic syndrome: Susceptibility and steroid responsiveness

BACKGROUND

Studies have investigated rs1128503, rs1045642, and rs2032582 in multidrug resistance protein 1 (MDR1) for association with susceptibility to idiopathic nephrotic syndrome (INS) and steroid resistance. However, because these findings were inconsistent, we performed a meta-analysis to determine whether there was evidence of a role of these MDR1 variants in INS.

METHODS

The PubMed, Embase, and Web of Science databases were systematically searched to identify studies that examined MDR1 polymorphisms with susceptibility to INS and/or to steroid resistance. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated by a fixed-effects or random-effects model based on heterogeneity.

RESULTS

We selected 9 case-control studies that included 928 patients with INS, of which steroid resistance data were available for 724 (236 were steroid resistant and 488 were steroid sensitive), and 879 healthy controls. All subjects were children. No significant relationships between these polymorphisms and INS susceptibility were identified. Significantly increased risk of steroid resistance was observed with rs1128503 allelic (OR = 1.49, 95% CI = 1.20-1.86) and genotypic (OR = 1.97, 95% CI = 1.18-3.30; OR = 2.03, 95% CI = 1.43-2.88) comparisons, and with allelic (OR = 1.56, 95% CI = 1.05-2.31) and genotypic (OR = 2.85, 95% CI = 1.15-7.07; OR = 2.21, 95% CI = 1.01-4.8) comparisons to rs2032582 in Caucasian populations. However, this association between rs2032582 and steroid resistance was not robust enough to withstand corrections for multiple comparisons. Similarly, we found that the rs1128503T-rs2032582G-rs1045642C (T-G-C) haplotype was associated with an increased risk of steroid resistance (OR = 2.02, 95% CI = 1.13-3.59), while the wild-type C-G-C haplotype was associated with a decreased risk (OR = 0.32, 95% CI = 0.12-0.88) in Caucasians; however, these findings were not significant following adjustments for multiple comparisons.

CONCLUSIONS

MDR1 rs1128503, rs1045642, and rs2032582 polymorphisms are not associated with INS susceptibility; however, there is evidence of an association between rs1128503 and increased risk of steroid resistance in children with INS, which indicates MDR1 may play a role in steroid resistance found in children with INS.

Genetic variation in the glucocorticoid pathway involved in interindividual differences in the glucocorticoid treatment

Glucocorticoids (GCs) are widely used for treating asthma, rheumatoid arthritis, nephrotic syndrome, acute lymphoblastic leukemia and other autoimmune diseases. However, in a subgroup of patients, failure to respond to GCs is known as GC resistance or GC insensitivity. This represents an important barrier to effective treatment and a clinical problem requiring an urgent solution. Genetic variation in the GC pathway is a significant factor in interindividual differences in GC treatment. This article reviews the pharmacogenetics of GCs in diverse diseases based on the GC pathway.

P-Glycoprotein Activity in Steroid-Responsive vs. Steroid-Resistant Nephrotic Syndrome

OBJECTIVES

To explore the expression of P-glycoprotein (P-gp) in the peripheral blood nucleated cells (PBNCs) of children with nephrotic syndrome in relation to their clinical response to glucocorticoid treatment.

METHODS

Thirty-six children with nephrotic syndrome (20 cases of steroid-responsive and 16 cases of steroid-resistant) were examined. All the participants were subjected to complete history taking, thorough clinical examination, laboratory investigations (24-h urinary protein, serum albumin, complete blood count with differential white blood cell count, serum cholesterol, serum urea, serum creatinine) and functional assay of P-gp using FACS Calibur flowcytometry. P-gp assay was done in both groups during remission.

RESULTS

P-gp activity was significantly higher in steroid-resistant than steroid-sensitive cases.

CONCLUSIONS

P-gp can be used as a predictor of outcome, as a part of laboratory evaluation of the cases before starting steroid therapy, so as to determine whether to use alternative line of therapy or use one of the P-gp inhibitors with steroid therapy.

Single Nucleotide Polymorphisms in Pediatric Idiopathic Nephrotic Syndrome

Polymorphic variants in several molecules involved in the glomerular function and drug metabolism have been implicated in the pathophysiology of pediatric idiopathic nephrotic syndrome (INS), but the results remain inconsistent. We analyzed the association of eleven allelic variants in eight genes (angiopoietin-like 4 (ANGPTL4), glypican 5 (GPC5), interleukin-13 (IL-13), macrophage migration inhibitory factor (MIF), neural nitric oxide synthetase (nNOS), multidrug resistance-1 (MDR1), glucocorticoid-induced transcript-1 (GLCCI1), and nuclear receptor subfamily-3 (NR3C1)) in 100 INS patients followed up till adulthood. We genotyped variants using PCR and direct sequencing and evaluated estimated haplotypes of MDR1 variants. The analysis revealed few differences in SNP genotype frequencies between patients and controls, or in clinical parameters among the patients. Genotype distribution of MDR1 SNPs rs1236, rs2677, and rs3435 showed significant (p < 0.05) association with different medication regimes (glucocorticoids only versus glucocorticoids plus additional immunosuppressives). Some marginal association was detected between ANGPTL4, GPC5, GLCCI1, and NR3C1 variants and different medication regimes, number of relapses, and age of onset. Conclusion. While MDR1 variant genotype distribution associated with different medication regimes, the other analyzed gene variants showed only little or marginal clinical relevance in INS.

Glucocorticoid pharmacogenetics in pediatric idiopathic nephrotic syndrome

Idiopathic nephrotic syndrome represents the most common type of primary glomerular disease in children: glucocorticoids (GCs) are the first-line therapy, even if considerable interindividual differences in their efficacy and side effects have been reported. Immunosuppressive and anti-inflammatory effects of these drugs are mainly due to the GC-mediated transcription regulation of pro- and anti-inflammatory genes. This mechanism of action is the result of a complex multistep pathway that involves the glucocorticoid receptor and several other proteins, encoded by polymorphic genes. Aim of this review is to highlight the current knowledge on genetic variants that could affect GC response, particularly focusing on children with idiopathic nephrotic syndrome.

Polymorphisms of the MDR1 and MIF genes in children with nephrotic syndrome

Oral steroid treatment is the first line of therapy for childhood nephrotic syndrome (NS). Nonetheless, some patients are resistant to this treatment. Many efforts have been made to explain the differences in the response to steroid treatment in patients with NS based on the genetic background. We have investigated single nucleotide polymorphisms of the MDR1 [C1236T (rs1128503), G2677T/A (rs2032582), and C3435T (rs1045642)] and MIF (G-173C, rs755622) genes in 170 children with NS. Of these children, 69 (40.6%) were initial steroid non-responders, and 23 (13.5% of total) developed chronic kidney disease. Renal biopsy findings, which were available for 101 patients, showed that 35 patients had minimal change lesion and 66 had focal segmental glomerulosclerosis. The frequencies of the MDR1 1236 CC (18.8 vs 7.2%) or TC (53.5 vs 43.5%) genotype and C allele (45.5 vs 29.0%) were significantly higher in the initial steroid responders than in the non-responders. Analysis of MDR1 three-marker haplotypes revealed that the frequency of the TGC haplotype was significantly lower in the initial steroid responders than in the non-responders (15.8 vs 29.0%). There was no association between the MIF G-173C polymorphism and clinical parameters, renal histological findings, and steroid responsiveness. These data suggest that the initial steroid response in children with NS may be influenced by genetic variations in the MDR1 gene.

Relationship between expression of Pad1 homologue and multidrug resistance of idiopathic nephrotic syndrome

BACKGROUND

Multidrug resistance is an occasionally seen phenomenon in children with idiopathic nephrotic syndrome (INS), but the mechanism of multidrug resistance is not clear as yet. The purpose of the present study was to investigated whether expression of Pad1 homologue (POH1) plays a role in the onset of multidrug resistance of INS.

METHODS

Comparison was done of the mRNA level of POH1 on real-time quantitative polymerase chain reaction in peripheral blood mononuclear cells among children with multidrug-resistant INS, children with steroid-sensitive INS and healthy controls.

RESULTS

The POH1 mRNA level of the onset INS group (5852.3 +/- 2676.4 copies/microg) was significantly lower than that of the control group (10 877.1 +/- 2386.6 copies/microg; P < 0.05). The POH1 mRNA level of the onset INS group with multidrug resistance was not significantly higher than that of the onset INS group without multidrug-resistance before treatment (6977.1 +/- 6312.3 copies/microg vs 5281.3 +/- 1926.7 copies/microg; P > 0.05), but significantly higher than that of the onset INS group without multidrug resistance after treatment (436 579.6 +/- 99 727.4 copies/microg vs 38 438.2 +/- 16 772.5 copies/microg; P < 0.001). The POH1 mRNA level of non-onset multidrug-resistant INS group (337 446.4 +/- 107 423.5 copies/microg) after treatment was not significantly higher than that of the onset INS group with multidrug resistance after treatment (436 579.6 +/- 99 727.4 copies/microg; P > 0.05), but was significantly higher than that of the onset INS group without multidrug resistance after treatment (38 438.2 +/- 16 772.5 copies/microg; P < 0.001).

CONCLUSIONS

Disorder of POH1 expression is involved in the onset of INS, and confers multidrug resistance in children with INS.

The anti-inflammatory effects of inhaled corticosteroids versus anti-leukotrienes on the lymphocyte P-glycoprotein (PGP) expression in asthmatic children

BACKGROUND

Inhaled corticosteroids (ICS) are used in asthma therapy for their anti-inflammatory effects. P-glycoprotein (PGP) is a transmembrane efflux pump for many drugs, including corticosteroids. Expression of PGP is associated with therapy resistant disease.

OBJECTIVE

The purpose of this study was to compare expression levels of PGP in blood lymphocytes of pediatric asthma patients either on ICS or on the leukotriene inhibitor montelukast medication.

PATIENTS AND METHODS

The evaluation of lymphocyte PGP expression was performed on a sample of 99 children (66 boys and 33 girls) aged 2-18 (median 12) years with intermittent or persisting mild asthma, (as defined by GINY 2002). The asthmatic children were divided into 3 groups: (1) treated by ICS budesonide 200-400 microg per day (n = 27) more than 1 year; (2) treated by oral montelukast 4 or 5 mg at an age-based dose (n = 16); and (3) treated by inhaled corticosteroids and montelukast (n = 45). Reference PGP values were obtained from a group of 64 healthy children (23 boys and 29 girls) aged 2-15 years (median, 10 years). The expression of lymphocyte PGP was determined on fixed and permeabilized blood mononuclear cells using indirect immunofluorescence staining technique by flow cytometry modified according to Boer et al., 1997.

RESULTS

Based on the weighted medians for PGP expression in peripheral blood lymphocytes, we found a significant difference (p < 10(-3)) between the group of asthma patients (n = 99), (619 +/- 5.3) and healthy controls (n = 64) (446.9 +/- 4.4). Second, there was a lower level of PGP expression in the group treated by ICS (548.6 +/- 9) than the group treated by montelukast and montelukast with budesonide (643.2 +/- 6.3) (p < 10(-6)).

CONCLUSIONS

The anti-inflammatory activity of ICS is more effective in decreasing the production of pro-inflammatory mediators and results in reduced multidrug resistence (MDR-1) gene activity and expression of lymphocyte PGP in asthmatic children.