Racial and Ethnic Disparities in Acute Care Utilization Among Patients With Glomerular Disease.

RATIONALE & OBJECTIVE: The effects of race, ethnicity, socioeconomic status (SES), and disease severity on acute care utilization in patients with glomerular disease are unknown. STUDY DESIGN: Prospective cohort study. SETTING & PARTICIPANTS: 1,456 adults and 768 children with biopsy-proven glomerular disease enrolled in the Cure Glomerulonephropathy (CureGN) cohort. EXPOSURE: Race and ethnicity as a participant-reported social factor. OUTCOME: Acute care utilization defined as hospitalizations or emergency department visits. ANALYTICAL APPROACH: Multivariable recurrent event proportional rate models were used to estimate associations between race and ethnicity and acute care utilization. RESULTS: Black or Hispanic participants had lower SES and more severe glomerular disease than White or Asian participants. Acute care utilization rates were 45.6, 29.5, 25.8, and 19.2 per 100 person-years in Black, Hispanic, White, and Asian adults, respectively, and 55.8, 42.5, 40.8, and 13.0, respectively, for children. Compared with the White race (reference group), Black race was significantly associated with acute care utilization in adults (rate ratio [RR], 1.76 [95% CI, 1.37-2.27]), although this finding was attenuated after multivariable adjustment (RR, 1.31 [95% CI, 1.03-1.68]). Black race was not significantly associated with acute care utilization in children; Asian race was significantly associated with lower acute care utilization in children (RR, 0.32 [95% CI 0.14-0.70]); no significant associations between Hispanic ethnicity and acute care utilization were identified. LIMITATIONS: We used proxies for SES and lacked direct information on income, household unemployment, or disability. CONCLUSIONS: Significant differences in acute care utilization rates were observed across racial and ethnic groups in persons with prevalent glomerular disease, although many of these difference were explained by differences in SES and disease severity. Measures to combat socioeconomic disadvantage in Black patients and to more effectively prevent and treat glomerular disease are needed to reduce disparities in acute care utilization, improve patient wellbeing, and reduce health care costs.

Increased Autophagy and Apoptosis in the Kidneys of Intrauterine Growth Restricted Rats.

BACKGROUND: IUGR has been associated with nephron loss and chronic kidney disease (CKD). MATERIALS AND METHODS: We examined autophagy and apoptosis markers in the kidneys of IUGR Sprague Dawley rats induced by maternal low protein diet (LP), comparing them to controls. The autophagy marker LC3B, the pro-apoptotic protein Bax, and the anti-apoptotic protein Bcl-2 were determined by quantitative immunoblotting. Immunohistochemical expressions of LC3B, Bax, and Bcl-2 were evaluated at 4 weeks age. Glomerular counts (by maceration techniques) were performed at 5 weeks. RESULTS: The LP diet offspring were lighter (P < 0.05). In IUGR kidneys, LC3B and Bax were increased at birth (p < 0.05, p < 0.001) and at 4 weeks (p < 0.0142, p < 0.0001), Bcl-2 was decreased at birth (p < 0.05), and there were less glomeruli (p < 0.01) at 5 weeks. CONCLUSIONS: Autophagy and apoptosis may have a role in IUGR associated decreased nephron number in Sprague rats.

Activation of the IL-2 Receptor in Podocytes: A Potential Mechanism for Podocyte Injury in Idiopathic Nephrotic Syndrome?

The renal podocyte plays an important role in maintaining the structural integrity of the glomerular basement membrane. We have previously reported that patients with idiopathic nephrotic syndrome (INS) have increased IL-2 production. We hypothesized that podocytes express an IL-2 receptor (IL-2R) and signaling through this receptor can result in podocyte injury. To confirm the presence of the IL-2R, we tested a conditionally immortalized murine podocyte cell line by flow cytometry, qPCR, and Western blot. To test for the presence of the IL-2R in vivo, immunohistochemical staining was performed on human renal biopsies in children with FSGS and control. Podocytes were stimulated with IL-2 in vitro, to study signaling events via the JAK/STAT pathway. The results showed that stimulation with IL-2 resulted in increased mRNA and protein expression of STAT 5a, phosphorylated STAT 5, JAK 3, and phosphorylated JAK 3. We then investigated for signs of cellular injury and the data showed that pro-apoptotic markers Bax and cFLIP were significantly increased following IL-2 exposure, whereas LC3 II was decreased. Furthermore, mitochondrial depolarization and apoptosis were both significantly increased following activation of the IL-2R. We used a paracellular permeability assay to monitor the structural integrity of a podocyte monolayer following IL-2 exposure. The results showed that podocytes exposed to IL-2 have increased albumin leakage across the monolayer. We conclude that murine podocytes express the IL-2R, and that activation through the IL-2R results in podocyte injury.

Intestinal microbiota in pediatric patients with end stage renal disease: a Midwest Pediatric Nephrology Consortium study.

BACKGROUND: End-stage renal disease (ESRD) is associated with uremia and increased systemic inflammation. Alteration of the intestinal microbiota may facilitate translocation of endotoxins into the systemic circulation leading to inflammation. We hypothesized that children with ESRD have an altered intestinal microbiota and increased serum levels of bacterially derived uremic toxins. METHODS: Four groups of subjects were recruited: peritoneal dialysis (PD), hemodialysis (HD), post-kidney transplant and healthy controls. Stool bacterial composition was assessed by pyrosequencing analysis of 16S rRNA genes. Serum levels of C-reactive protein (CRP), D-lactate, p-cresyl sulfate and indoxyl sulfate were measured. RESULTS: Compared to controls, the relative abundance of Firmicutes (P = 0.0228) and Actinobacteria (P = 0.0040) was decreased in PD patients. The relative abundance of Bacteroidetes was increased in HD patients (P = 0.0462). Compared to HD patients the relative abundance of Proteobacteria (P = 0.0233) was increased in PD patients. At the family level, Enterobacteriaceae was significantly increased in PD patients (P = 0.0020) compared to controls; whereas, Bifidobacteria showed a significant decrease in PD and transplant patients (P = 0.0020) compared to control. Alpha diversity was decreased in PD patients and kidney transplant using both phylogenetic and non-phylogenetic diversity measures (P = 0.0031 and 0.0003, respectively), while beta diversity showed significant separation (R statistic = 0.2656, P = 0.010) between PD patients and controls. ESRD patients had increased serum levels of p-cresyl sulfate and indoxyl sulfate (P < 0.0001 and P < 0.0001, respectively). The data suggests that no significant correlation exists between the alpha diversity of the intestinal microbiota and CRP, D-lactate, or uremic toxins. Oral iron supplementation results in expansion of the phylum Proteobacteria. CONCLUSIONS: Children with ESRD have altered intestinal microbiota and increased bacterially derived serum uremic toxins.

T cell CD3 receptor zeta (TCRzeta)-chain expression in children with idiopathic nephrotic syndrome.

Children with idiopathic nephrotic syndrome (INS) have an increased risk of developing life-threatening infections. Several studies have demonstrated functional abnormalities in the T lymphocytes of patients with nephrotic syndrome. Although T cells are activated in INS during relapse, as indicated by an increased expression of interleukin (IL)-2 receptor, these cells have a decreased ability to proliferate. The T-cell receptor (TCR) plays an important role in signal transduction and T cell activation, with the TCR-zeta (TCRzeta) chain being a key element in early signaling. We measured the expression of the TCRzeta chain in patients with INS (steroid resistant and steroid sensitive) during relapse and remission by flow cytometry and by PCR ELISA. The results showed a significant decrease in the expression of the TCRzeta chain at both the protein and mRNA level in INS patients during relapse as compared with normal controls (p < 0.05). In contrast, when patients with INS achieved remission, the expression of TCRzeta normalized and was similar to that expressed in normal controls. Therefore, a decreased expression of the TCRzeta chain may explain the abnormal function of T cells in patients with INS, and it may also contribute to the increased risk for infections seen in these patients.

Effect of arginase II on L-arginine depletion and cell growth in murine cell lines of renal cell carcinoma.

BACKGROUND: L-arginine is the common substrate for the two isoforms of arginase. Arginase I, highly expressed in the liver and arginase II mainly expressed in the kidney. Arginase I-producing myeloid derived suppressor cells have been shown to inhibit T-cell function by the depletion of L-arginine. On the other hand, arginase II has been detected in patients with cancer and is thought to metabolize L-arginine to L-ornithine needed to sustain rapid tumor growth; however its role in L-arginine depletion is unclear. Thus, in tumor biology, L-arginine metabolism may play a dual role in tumor growth and in the induction of T cell dysfunction. Therefore, we studied in murine renal cell carcinoma (RCC) cell lines, the effect of arginase II on tumor cell proliferation and L-arginine depletion. The effect of arginase inhibitors on cell proliferation was also tested. METHODS: Three murine renal cell carcinoma (mRCC) cell lines were tested for the presence of arginase. nor-NOHA, an arginase inhibitor was used to substantiate the effect of arginase on cell growth and L-arginine depletion. Amino acid levels were tested by HPLC. RESULTS: Our results show that mRCC cell lines express only arginase II and were able to deplete L-arginine from the medium. Cell growth was independent of the amount of arginase activity expressed by the cells. nor-NOHA significantly (P = 0.01) reduced arginase II activity and suppressed cell growth in cells exhibiting high arginase activity.The depletion of L-arginine by mRCC induced the decrease expression of CD3zeta a key element for T-cell function. CONCLUSION: The results of this study show for the first time that arginase II produced by RCC cell lines depletes L-arginine resulting in decreased expression of CD3zeta. These results indicate that RCC cell lines expressing arginase II can modulate the L-arginine metabolic pathway to regulate both cell growth and T-cell function. Blocking arginase may lead to a decrease in RCC cell growth and aid in restoring immune function by increasing L-arginine availability for T-cell use. Understanding the interplay between arginase II and its interaction with the immune system may provide future therapeutic benefits to treat patients with RCC.

Treatment of primary and secondary hypertension in children.

The incidence of pediatric hypertension (HTN) is increasing, mainly due to an increase in primary (essential) HTN, or PH. There are only a limited number of studies assessing the characteristics and treatment efficacy of PH versus secondary HTN (SH). We conducted a retrospective analysis of 158 pediatric patients (mean age: 10.8 years; sex ratio: 51.1% female, 48.9% male) with HTN of whom 34.4% had PH and 65.6% had SH. The vast majority were either African-American or Caucasian. Among all patients, therapy induced a significant decrease in systolic blood pressure (SBP) and diastolic BP (DBP) (both p<0.0001). SBP (p<0.0001) and DBP (p=0.002) declined significantly in PH patients. PH and SH patients with a body mass index (BMI) >95th percentile (%) had a significantly higher post-therapy SBP (both p<0.05) than those with a BMI <95th%. SBP declined similarly in PH patients treated with calcium-channel blockers (CCB) and angiotensin-converting enzyme inhibitors (ACEI). DBP declined only in PH patients treated with ACEI. SBP and DBP (both p<0.0001) declined significantly in SH patients. Post-therapy BP was similar in SH patients treated with either CCB or ACEI. Post-therapy SBP and DBP were significantly lower in SH patients than in PH patients; moreover, therapy induced a greater decline in SBP and DBP in the SH patients. Compared to PH patients, SH patients were twofold more likely to achieve a SBP less than the 95th% after therapy. We conclude that (1) significant lowering of BP with either CCB or ACEI is achievable in most children with HTN, and (2) SH patients respond better to therapy than those with PH.

Effect of age, ethnicity, and glucocorticoid use on tacrolimus pharmacokinetics in pediatric renal transplant patients.

Tacrolimus has become an effective alternative to cyclosporine as a component of primary immunosuppression in pediatric renal transplant patients, but the information on the pharmacokinetic characteristics of tacrolimus in young patients is still limited. The primary objective of this study was to determine the effect of patient age, ethnicity, and concurrent steroid administration on tacrolimus pharmacokinetics in pediatric renal transplant patients. The study population consisted of 30 pediatric patients, age 1.5-18.6 yr, who received a kidney transplant between July 1999 and February 2004. After twice daily dosing was stabilized based on clinical judgment, at least 5 days postoperatively, tacrolimus levels were drawn prior to, and 1, 2, 4, 8, and 12 h after the morning dose. The mean dose of tacrolimus was 0.12 mg/kg/dose. Mean trough level was 11.9 +/- 5.0 ng/mL. Mean area under the curve (AUC) was 192 +/- 84 with a range of 78-360 h x (ng/mL). The correlation between trough level and AUC was only fair (r = 0.74); later time points correlated better with AUC, and an excellent correlation (r = 0.96) was obtained between the mean of trough and 2-h level (C(2)) and AUC. There was a negative correlation between age and dose per body weight (r = -0.68). African-American patients had marginally lower drug exposure with similar dosing. Three age groups (<5, 5-12, and >12 yr) were compared with respect to dosing and AUC. Despite similar AUC in all three groups, the mean dose per kg required to achieve the AUC was 2.7- and 1.9-fold higher in the <5 and 5-12-yr groups, respectively, compared with the >12-yr group. Nine of the 30 patients were on a totally steroid-free regimen. Their tacrolimus dose and trough levels were similar to those of steroid-exposed patients, but their mean AUC was 41% higher. Our results show an inverse correlation between age and required tacrolimus dose, wide interindividual variation, and greater exposure with steroid-free regimen despite no change in trough level.

Results of one-year follow-up of steroid-free immunosuppression in pediatric renal transplant patients.

Renal transplantation in children has traditionally required immunosuppression with multiple medications including glucocorticoids. Data collected over almost 30 yr suggest that although glucocorticoids are efficacious as part of a regimen to minimize the incidence of acute rejection episodes, their use is associated with increased risk for post-transplant hypertension, hyperlipidemia, and reduced growth rates. We desired to reduce these complications and thus used an immunosuppressive protocol including daclizumab, tacrolimus, and mycophenolate mofetil and study the efficacy of this protocol in a population with a high percentage of African-American recipients. No patient received glucocorticoids at any time post-transplant. Our results show that at 1 yr post-transplant, glomerular filtration rate, serum glucose, calcium and phosphorous metabolism, serum magnesium, and serum lipids were similar in patients receiving steroid-free and those receiving steroid-based immunosuppression. The incidence of acute rejection was similar in the two groups. Hematocrit and white blood count levels were lower 1 month after transplant in the steroid-free patients but these levels increased within several months. Systolic blood pressure was similar in the two groups, although this was achieved, in part, in the patients who received steroids by the administration of medications to lower blood pressure. Finally, tacrolimus levels were similar in the two groups, but patients receiving steroids required higher doses of tacrolimus at several time points studied during the first post-transplant year. Taken together, our data suggests that at one-year follow-up, steroid-free immunosuppression is safe, and efficacious in pediatric renal transplant recipients.

High incidence of initial and late steroid resistance in childhood nephrotic syndrome.

BACKGROUND: Conventional wisdom states that greater than 80% of children with nephrotic syndrome (NS) respond to steroid treatment, remain steroid-sensitive during subsequent relapses, and consequently have a favorable long-term prognosis. In contrast, steroid resistance is believed to be associated with a high risk of developing chronic renal failure. Recent reports suggest that the histologic pattern of NS in children may be changing, but whether the change is accompanied by a parallel change in steroid sensitivity is unknown. METHODS: Initial and subsequent steroid responsiveness was evaluated in all children aged 1 to 18 years who presented with newly diagnosed NS to the 2 pediatric nephrology referral centers in southeastern Louisiana between 1994 and 2003. NS was defined as presence of edema, heavy proteinuria, and serum albumin concentration below 2.5 g/dL. Steroid sensitivity (SS) was defined as total resolution of proteinuria and edema, and partial response to steroids (PR) was defined as loss of edema with continuing proteinuria. RESULTS: There were 210 new cases of NS. Forty-one patients (20%) had immune complex glomerulonephritis. Six patients were excluded because of incomplete data availability. Of the remaining 163 patients, 115 (71%) were SS and 23 (14%) achieved PR during the initial 4 weeks of treatment; 25 (15%) were steroid-resistant (SR). Follow-up data were available for 91 of the 115 initially SS patients; 19 subsequently became steroid-resistant. Thus, at least 45% of the patients with new-onset NS did not have typical childhood steroid-responsive NS. Initial steroid resistance was more likely in African American children and in children with older age at onset (11.5 vs. 4.6 years). Development of steroid resistance after initial SS was associated with shorter interval to the first relapse (2.2 vs. 5.4 months) and having the first relapse during the initial steroid treatment. CONCLUSION: Compared to previous reports, our results show a higher incidence of initial and subsequent steroid resistance, characteristics not consistent with typical minimal change NS with a benign prognosis. The results suggest that in the current era, NS in children may not be as benign as indicated by earlier studies.

False-positive human immunodeficiency virus antibody test in a dialysis patient.

A patient developed end-stage renal disease secondary to p-anti-neutrophil cytoplasmic antibody (p-ANCA) positive rapidly progressive glomerulonephritis. He subsequently had human immunodeficiency virus (HIV)-1 antibody screening performed as part of a pre-transplant evaluation. The HIV-1 enzyme immunoassay (EIA) antibody test was repeatedly reactive. The HIV-1 western blot was indeterminate. The western blot pattern revealed "non-specific staining obscuring bands in that region." Another sample of serum was sent and the results were identical to the first result. An HIV-1 proviral qualitative polymerase chain reaction test was then performed several months later and no HIV-1 DNA was detected. One year later, an HIV-1 RNA test was negative. Thus, the positive antibody EIA test and the indeterminate western blot represent a false-positive result, most likely due to cross-reacting antigens in the patient's serum with various HIV antibodies. Throughout this period and thereafter, the patient has exhibited no symptoms of HIV infection.

Sudden blindness in a child with end-stage renal disease.

Continuous peritoneal dialysis (CPD) is the preferred modality for renal replacement therapy in children with end-stage renal disease. Anterior ischemic optic neuropathy (AION) is a rare complication in patients on CPD. AION is characterized by ischemic injury of the optic nerve caused by hypoperfusion of the posterior ciliary arteries. It presents with acute visual loss and disc swelling, without additional neurological findings. We report a 2-year-old child with end-stage renal disease on CPD who developed AION. He was dehydrated and received intravenous fluid on admission. Additional treatment included methylprednisolone and levodopa. On his 3rd admission day, his pupils became reactive to light and his vision showed improvement. The improvement in vision might be due to the early detection and aggressive treatment of hypotension. It is difficult to demonstrate whether steroids or levodopa played a role in the improvement of his vision. Prospective studies to evaluate the effectiveness of levodopa in the treatment of AION are warranted in this potentially devastating condition.

Decreased expression of T-cell NF-kappaB p65 subunit in steroid-resistant nephrotic syndrome.

BACKGROUND: Although the etiology of childhood nephrotic syndrome is unclear, there is evidence to suggest an important role for T cells in the pathogenesis. Steroid resistance is considered a poor prognostic sign but the mechanism of the resistance is unknown. The study examined the potential role of T-cell nuclear transcription factors in the steroid resistance. METHODS: The expression of the nuclear transcription factors activating protein-1 (AP-1) and nuclear factor-kappaB (NF-kappaB) as well as that of lymphokines interleukin (IL)-2, IL-4, and interferon-gamma (IFN-gamma) were compared in T cells obtained from normal subjects, children with steroid-sensitive nephrotic syndrome (SSNS) and children with steroid-resistant nephrotic syndrome (SRNS) before any treatment was given. Changes in expression and binding of the nuclear transcription factors were studied with electrophoretic mobility shift assay (EMSA) and Western blot, whereas mRNA cytokine expression were evaluated by enzyme-linked immunosorbent assay (ELISA)-linked reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: A significant decrease of the p65 subunit protein of NF-kappaB but not in p50 was documented by both EMSA (N= 7) and Western blotting (N= 5) in five of five SRNS patients but not in control subjects or SSNS patients; there was a decrease in mRNA expression as shown by ELISA-linked RT-PCR. In contrast, there were no significant differences in AP-1 expression by EMSA. IL-2 mRNA level was higher in T cells from SRNS patients than in T cells from either SSNS or control subjects. IL-4 and IFN-gamma were equally decreased in both groups of patients. CONCLUSION: The results show differences in T cells between untreated SSNS and SRNS patients. The decrease of NF-kappaB p65 subunit and up-regulation of IL-2 are potential mechanism of glucocorticoid resistance in SRNS.