Optimal peritoneal fluid white blood cell count for diagnosis of peritonitis in peritoneal dialysis patients.

BACKGROUND: The diagnosis of peritonitis among peritoneal dialysis (PD) patients is based on clinical presentation, dialysis effluent white blood cell (WBC) count, and dialysis effluent culture. Peritoneal fluid WBC count is very important in the initial diagnosis of peritonitis. The purpose of this work was to determine the optimal number of peritoneal WBCs with different clinical presentations at admission to define PD-related peritonitis. METHODS: Medical records of chronic PD patients who underwent work-up for suspected peritonitis between 2008 and 2019 were reviewed retrospectively. Results of all peritoneal WBC count tests during this period were collected. Clinical manifestations and follow-up analysis of each peritoneal WBC count were performed. RESULTS: The peritoneal WBC count cutoff of 100/µL recommended by International Society for Peritoneal Dialysis provided specificity of only 35%. Increasing peritoneal WBC count cutoff to 150, 200, and 250/µL provided sensitivity around 98% and gradually increasing specificity. The chi-square automatic interaction detector model of statistical analysis determined that peritoneal WBC count below 230/µL combined with absence of inflammatory markers (fever, increased C-reactive protein) ruled out peritonitis with 99.8% sensitivity. Peritoneal fluid WBC count cutoff of 230/µL provided specificity of 89% and good positive and negative likelihood scores of 8.3 and 0.03, respectively. Peritoneal fluid polymorphonuclear count has lower discriminating ability for peritonitis compared to peritoneal fluid WBC count. CONCLUSION: Increasing peritoneal fluid WBC count cutoff to 230/µL in suspected PD-related peritonitis could improve specificity without compromising the sensitivity of the test.

Acute Kidney Injury following Exposure to Formaldehyde-Free Hair-Straightening Products.

Formaldehyde-free hair-straightening products are hair-smoothening solutions widely used by professional beauty salons. Formaldehyde-free hair straighteners do not technically contain formaldehyde; however, they contain other chemicals such as glyoxyloyl carbocysteine which releases formaldehyde upon contact with heat. Moreover, its by-product glyoxylate may convert to oxalate; both compounds have potential nephrotoxic effect. Here, we report a case of a 41-year-old woman who presented to the emergency room with weakness, nausea, vomiting, and stage 3 acute kidney injury (AKI) according to Kidney Disease: Improving Global Outcomes (KDIGO) acute kidney injury staging shortly after exposure to formaldehyde-free hair-straightening product; other causes of AKI were excluded such as preceding acute illness, drug history, or other nephrotoxic agent exposure. On physical examination, the patient was pale, and her vital signs were normal. The urine microscopy and serologic workup were not indicative. Kidney core biopsy revealed interstitial edema, acute interstitial nephritis, and oxalate crystal nephropathy. Kidney function completely recovered after a short course of steroid therapy. In this case, AKI was a complication caused by exposure to hair-straightening products branded as formaldehyde free but actually containing other chemical products which release formaldehyde and other toxic chemicals when heated during the straightening procedure and may cause systemic toxicity, particularly kidney injury. Different cosmetic products are widely in use, but not all are under tight regulation, and therefore, it is important to raise the awareness among both medical teams and consumers of possible adverse health effects of different cosmetic products.

The Peritoneal Membrane-A Potential Mediator of Fibrosis and Inflammation among Heart Failure Patients on Peritoneal Dialysis.

Peritoneal dialysis is a feasible, cost-effective, home-based treatment of renal replacement therapy, based on the dialytic properties of the peritoneal membrane. As compared with hemodialysis, peritoneal dialysis is cheaper, survival rate is similar, residual kidney function is better preserved, fluid and solutes are removed more gradually and continuously leading to minimal impact on hemodynamics, and risks related to a vascular access are avoided. Those features of peritoneal dialysis are useful to treat refractory congestive heart failure patients with fluid overload. It was shown that in such patients, peritoneal dialysis improves functional status and quality of life, reduces hospitalization rate, and may decrease mortality rate. High levels of serum proinflammatory cytokines and fibrosis markers, among other factors, play an important part in congestive heart failure pathogenesis and progression. We demonstrated that those levels decreased following peritoneal dialysis treatment in refractory congestive heart failure patients. The exact mechanism of beneficial effect of peritoneal dialysis in refractory congestive heart failure is currently unknown. Maintenance of fluid balance, leading to resetting of neurohumoral activation towards a more physiological condition, reduced remodeling due to the decrease in mechanical pressure on the heart, decreased inflammatory cytokine levels and oxidative stress, and a potential impact on uremic toxins could play a role in this regard. In this paper, we describe the unique characteristics of the peritoneal membrane, principals of peritoneal dialysis and its role in heart failure patients.

Treatment of Severe Renal Artery Stenosis with Acute Kidney Injury Requiring Hemodialysis by Percutaneous Transluminal Renal Angioplasty and Stent Implantation.

PURPOSE: To evaluate the outcomes of percutaneous transluminal renal angioplasty with stent implantation (PTRAS) among patients with renal artery stenosis (RAS) who become dialysis-dependent due to acute deterioration of renal function. MATERIALS AND METHODS: This was a single-center retrospective cohort study of all PTRAS procedures performed from 2003 to 2019 in a referral hospital. A total of 109 procedures were performed in 92 patients. Eleven patients (12%) presented with anuric acute kidney injury (AKI) secondary to high-grade RAS (defined as intraluminal stenosis above 70% per angiography) and underwent PTRAS after starting hemodialysis. Data collected included demographic parameters, medical background, creatinine, blood pressure, indication for intervention, procedure characteristics, adverse events, and long-term data including dialysis treatment and mortality. Among the dialysis-dependent AKI group, outcome measures were defined based on the postprocedural improvement in kidney function and discontinuation of dialysis. RESULTS: Following PTRAS, 8 of 11 patients (73%) demonstrated improved kidney function and were able to discontinue dialysis. The median time on dialysis was 18 days (range, 2-35 days) before PTRAS and 4.5 days (range, 1-24 days) to recovery of kidney function after the time of intervention. CONCLUSIONS: Patients with atherosclerotic RAS who develop RAS-related AKI may benefit from PTRAS even after several weeks of anuria and dialysis dependence.

Regular at-home abdominal paracentesis via Tenckhoff catheter in patients with refractory congestive heart failure.

BACKGROUND: Peritoneal dialysis (PD) is increasingly used for the long-term management of refractory congestive heart failure (CHF). Patients with severe CHF and ascites were treated with regular at-home abdominal paracentesis via Tenckhoff catheter. We investigated the outcome of those patients, aiming to identify potential prognostic factors for longer survival. METHODS: Patients with refractory CHF referred by cardiologists to the PD unit from years 2009 to 2019 and treated with regular at-home abdominal paracentesis via Tenckhoff catheter without peritoneal exchanges, were enrolled into this prospective observational study. RESULTS: From the total of 69 refractory CHF patients treated with PD, 18 (26%) were managed with regular at-home abdominal paracentesis via Tenckhoff catheter and improved without the need for peritoneal exchanges for fluid removal (no peripheral oedema or pulmonary congestion) or for solutes removal. Median survival of severe CHF patients treated with abdominal paracentesis was 13.5 months (0-34 months). Long-term survivors demonstrated significant improvement in the New York Heart Association (NYHA) functional class, improvement in kidney function and decrease in serum C-reactive protein (CRP) and Brain natriuretic peptide (BNP) compared with their baseline status. A subgroup of patients with shorter survival were more likely to have evidence of liver cirrhosis and significantly lower serum sodium compared with patients with longer survival. CONCLUSIONS: Refractory CHF patients with massive ascites could be successfully treated with regular at-home abdominal paracentesis via Tenckhoff catheter. This treatment provides a useful alternative to periodical percutaneous paracentesis on as-needed basis.

Nontuberculous mycobacteria infections of peritoneal dialysis patients: A multicenter study.

OBJECTIVES: Nontuberculous mycobacteria (NTM) infections pose a diagnostic challenge in peritoneal dialysis (PD) patients. In this study, we sought to identify findings that are suggestive of NTM infection in PD adult patients. METHODS: All patients with NTM exit-site infection (ESI) with/without tunnel infection and peritonitis identified during the last decade in eight medical centers in Israel were included. Clinical, microbiological, and outcome data were collected and analyzed. RESULTS: Thirty patients were identified; 16 had ESI (53%) and 14 had peritonitis (47%). Median age was 65 years (interquartile range 52-76). Abdominal pain and cloudy PD fluid were reported in all patients with peritonitis, whereas exit-site discharge and granulation tissue were common in patients with ESI. Fourteen patients (47%) had negative cultures prior NTM diagnosis, and isolation of diphtheroids or Corynebacterium spp. was reported in 9 of 30 patients (30%). Antimicrobial treatment prior to diagnosis was documented in 13 of 30 patients (43%). Delayed diagnosis was frequent. Treatment regimens and duration of therapy varied widely. In 26 of 30 (87%) patients, catheter was removed and 19 of 30 patients (63%) required permanent transition to hemodialysis. Two patients with peritonitis (2 of 14, 14%) and seven with ESI (7 of 16, 44%) were eligible for continuation of PD. CONCLUSIONS: Culture negative peritonitis, isolation of diphtheroids or Corynebacterium spp., previous exposure to antibiotics, and/or a refractory infection should all prompt consideration of PD-related NTM infection and timely workup. Catheter removal is recommended aside prolonged antimicrobial therapy. In select patients with ESI, continuation of PD may be feasible.

Congestive heart failure treated with peritoneal dialysis or hemodialysis: Typical patient profile and outcomes in real-world setting.

BACKGROUND: Peritoneal dialysis (PD) is increasingly used for the long-term management of hypervolemic refractory congestive heart failure (CHF) patients, in particular when complicated by renal insufficiency. While PD has many advantages over hemodialysis (HD) in those patients, there is a controversy concerning survival superiority of PD compared with HD in this population. The aim of the study was to define typical patient profile and to compare outcomes of patients with CHF and renal failure treated with HD or PD. METHODS: This retrospective cohort study enrolled CHF patients treated with chronic PD or HD between the years 2009-2018. Information at dialysis initiation included age, gender, body weight, blood pressure, cause of renal disease, comorbidities, hospitalisations, echocardiographic and laboratory parameters. Survival was compared between PD and HD patients using a Kaplan-Meier model and Cox regression analysis. RESULTS: CHF patients treated with PD had significantly higher eGFR and lower systolic blood pressure compared with HD treated patients. Median survival time was 13.32 (7.08, 23.28) months in the PD group and 19.68 (9.48, 39.24) months in the HD group, P = .013. After adjustment for confounders the mortality risk amongst PD and HD patients was not significantly different: adjusted HR for death in PD vs HD patients was 1.44, P = .35 for 1- year and 1.69, P = .10 for 2-year mortality. Number of hospitalisations was similar in both groups. CONCLUSIONS: CHF patient profile was different in PD and HD. Two modalities were equally effective in the treatment of patients with CHF and renal failure considering different patient characteristics.

Effect of Peritoneal Dialysis on Serum Fibrosis Biomarkers in Patients with Refractory Congestive Heart Failure.

BACKGROUND: Cardiac collagen remodeling is important in the progression of heart failure. Estimation of cardiac collagen turnover by serum levels of serological markers is used for monitoring cardiac tissue repair and fibrosis. Peritoneal dialysis (PD) is used for the long-term management of refractory congestive heart failure (CHF). In this study, we investigated the effect of PD treatment on circulating fibrosis markers levels in patients with refractory CHF and fluid overload. METHODS: Twenty-five patients with refractory CHF treated with PD were prospectively enrolled in the study. Circulating fibrosis markers procollagen type III C-peptide (PIIINP), matrix metalloproteinase 2 (MMP-2), and tissue inhibitor of metalloproteinases I (TIMP-1) levels were checked at baseline and after three and six months of treatment. RESULTS: The clinical benefit of PD manifested by improved NYHA functional class and reduced hospitalization rate. Serum brain natriuretic peptide (BNP) levels decreased significantly during the treatment. Serum MMP-2 and TIMP-1 decreased significantly on PD. Circulating PIIINP showed two patterns of change, either decreased or increased following PD treatment. Patients in whom circulating PIIINP decreased had significantly lower baseline serum albumin, lower baseline mean arterial blood pressure, higher serum CRP, and a less significant improvement in hospitalization rate compared to the patients in whom circulating PIIINP increased. Patients in whom all three markers decreased demonstrated a trend to longer survival compared to patients whose markers increased or did not change. CONCLUSION: In refractory CHF patients PD treatment was associated with a reduction in circulating fibrosis markers.

Hyponatremia in refractory congestive heart failure patients treated with icodextrin-based peritoneal dialysis: A case series / Hiponatremia en pacientes con insuficiencia cardíaca congestiva resistentes al tratamiento tratados con diálisis peritoneal con icodextrina: una serie de casos

Severe congestive heart failure (CHF) patients are prone to hyponatremia. Peritoneal dialysis (PD) is increasingly used for long-term management of refractory CHF patients. The glucose polymer icodextrin was proposed to be a good option for fluid removal in such patients. A small, although statistically significant reduction in serum sodium (∼2mmol/l) consistently observed in multiple trials, is considered as not clinically relevant. Here we reported five refractory CHF patients who demonstrated sodium drop by median of 8meq/l (range 5.4-8.3meq/l) after icodextrin was added to their program. It seems that icodextrin may contribute to clinically relevant hyponatremia if the hyponatremia is compounded by other factors. Patients with extremely severe congestive heart failure are susceptible to this complication (AU)

Los pacientes con insuficiencia cardíaca congestiva grave son propensos a sufrir hiponatremia. La diálisis peritoneal se utiliza cada vez más para el tratamiento a largo plazo de los pacientes con insuficiencia cardíaca congestiva resistentes al tratamiento. El polímero de glucosa icodextrina se propuso como una buena opción para la ultrafiltración. Una reducción pequeña, aunque estadísticamente significativa, del sodio sérico (∼2mmol/l) observada sistemáticamente en numerosos ensayos no se considera de relevancia clínica. En este documento informamos de 5 casos de pacientes con insuficiencia cardíaca congestiva resistentes al tratamiento que presentaron una caída de las concentraciones de sodio en una mediana de 8mEq/l (intervalo 5,4-8,3mEq/l) después de la adición de icodextrina a su programa. Parece ser que la icodextrina puede contribuir a una hiponatremia clínicamente relevante si se combina con otros factores. Los pacientes con insuficiencia cardíaca congestiva muy grave son propensos a esta complicación (AU)

Intraperitoneal antibiotic administration for prevention of postoperative peritoneal catheter-related infections.

BACKGROUND: It is recommended that systemic prophylactic antibiotics be given immediately prior to peritoneal catheter insertion. This administration requires intravenous access and could be inconvenient in dynamic and unpredictable operation room schedule. Intraperitoneal antibiotics could be an alternative simple way for prevention of postoperative peritoneal catheter infections. METHODS: Medical records from 109 patients undergoing permanent PD catheter placement procedures were reviewed retrospectively. Group I patients (66 patients) received intraperitoneal cefazolin through the inserted Tenckhoff catheter in operation room. Group II (43 patients) received intravenous cefazolin 2 h prior to the surgery. The effect of prophylactic antibiotics on the occurrence of peritonitis and exit site infection in the 14 days following surgical peritoneal dialysis catheter placement was evaluated. RESULTS: During the follow-up period, one patients from group II (2.3%) and none from group I developed peritonitis (P = 0.3945). One patient from each group developed exit site infection (P = 1.000). CONCLUSION: It was found that intraperitoneal antibiotics have the similar efficacy compared with intravenous antibiotics for postoperative peritoneal catheter-related infections' prevention. It does not require intravenous access and overcome the issue of unpredictable operation room schedule.

Hyponatremia in refractory congestive heart failure patients treated with icodextrin-based peritoneal dialysis: A case series.

Severe congestive heart failure (CHF) patients are prone to hyponatremia. Peritoneal dialysis (PD) is increasingly used for long-term management of refractory CHF patients. The glucose polymer icodextrin was proposed to be a good option for fluid removal in such patients. A small, although statistically significant reduction in serum sodium (∼2mmol/l) consistently observed in multiple trials, is considered as not clinically relevant. Here we reported five refractory CHF patients who demonstrated sodium drop by median of 8meq/l (range 5.4-8.3meq/l) after icodextrin was added to their program. It seems that icodextrin may contribute to clinically relevant hyponatremia if the hyponatremia is compounded by other factors. Patients with extremely severe congestive heart failure are susceptible to this complication.

Inflammatory Biomarkers in Refractory Congestive Heart Failure Patients Treated with Peritoneal Dialysis.

Proinflammatory cytokines play a pathogenic role in congestive heart failure. In this study, the effect of peritoneal dialysis treatment on inflammatory cytokines levels in refractory congestive heart failure patients was investigated. During the treatment, the patients reached a well-tolerated edema-free state and demonstrated significant improvement in NYHA functional class. Brain natriuretic peptide decreased significantly after 3 months of treatment and remained stable at 6 months. C-reactive protein, a plasma marker of inflammation, decreased significantly following the treatment. Circulating inflammatory cytokines TNF-α and IL-6 decreased significantly after 3 months of peritoneal dialysis treatment and remained low at 6 months. The reduction in circulating inflammatory cytokines levels may be partly responsible for the efficacy of peritoneal dialysis for refractory congestive heart failure.

Peritoneal dialysis in patients with refractory congestive heart failure: potential prognostic factors.

BACKGROUND: Peritoneal dialysis (PD) is increasingly used for long-term management of refractory congestive heart failure (CHF). In this study, we investigated the outcome of patients with refractory CHF treated with PD, aiming to identify potential prognostic factors for long term-survival. METHODS: This was a prospective observational study over a period of 42 months which included 37 refractory CHF patients. RESULTS: Median survival on PD was 14 months (1-41 months). Long survivors had serum sodium >132 mEq/l (p < 0.001), serum albumin >3.2 g/dl (p < 0.001) and hospitalization rate <2 days per month a year before starting the treatment (p = 0.008). Patients in the lowest survival quartile had lower serum albumin (2.8 vs. 3.5 g/dl in longer survivors, p = 0.003) and serum sodium (126 vs. 137 mEq/l, p < 0.0001), higher serum leukocyte count (7,500 vs. 6,800/µl in long survivors, p = 0.033), higher glomerular filtration rate (39.4 vs. 29.9 ml/min/1.73 m(2), p = 0.035), had more hospitalization before starting the treatment (3.4 vs. 1.9 days per month, p = 0.003) and lower estimated left ventricular mass index (113 vs. 137 g/m(2), p = 0.035). Long-term survivors demonstrated significant improvement in the New York Heart Association functional class by a median of one class, reduced hospitalization rate by 55% and decrease in dependence on intravenous diuretics and vasoactive medications (73% drop in CHF day care visits during the first year of treatment). CONCLUSIONS: Survival of patients with refractory CHF treated with PD is highly variable. Serum sodium, serum albumin and hospitalization rate are important prognostic factors for long-term survival. Long survivors demonstrated improved functional status, reduced hospitalization and mortality rates.

Urinary organic anion transporter protein profiles in AKI.

BACKGROUND: Organic anion transporters (OATs) are located on either the basolateral or the apical membrane of the proximal tubule cell and mediate the absorption and secretion of various drugs and endogenous metabolites. It has been shown that cellular damage in acute kidney injury (AKI) involves three forms of injury: sublethal damage resulting in loss of cell polarity, cell death through apoptosis and necrosis. We hypothesize that cellular mistargeting of OAT proteins in AKI will change the profile of OAT proteins in urine. METHODS: Thirty AKI patients were included in the study. AKI was defined by clinical course, daily urine output, response to fluid repletion, urinary sediment, fractional excretion of sodium (FeNa) and urine osmolality. Urinary OAT1, OAT3 and OAT4 protein abundance was measured from semiquantitative immunoblots of urine membrane fraction samples (exosome) collected from patients with AKI and from control subjects. RESULTS: Although all patients studied reached a similar severity of renal failure measured by serum creatinine, some of them recovered from AKI with supportive care only, while others required renal replacement therapy (RRT). OAT1 and OAT3, which are normally localized in the basolateral membrane of the proximal tubule cell, were detected at low levels in urine from control subjects and were increased significantly in all patients with AKI. OAT4 protein, which is normally localized in the luminal membrane of proximal tubule cells, was present in abundance in urine of control subjects. Interestingly, in patients with AKI who eventually recovered, urinary OAT4 was found to be significantly lower than in controls, while in patients who needed RRT, it was higher than in controls. CONCLUSIONS: We have shown that OATs are mistargeted in AKI. The urinary OAT protein profile can help us to learn about the pathophysiology of the disease and might be a marker of AKI severity. AKI patients with early reversible proximal tubular damage will have high urine OAT1 and OAT3 and low OAT4, while patients with severe AKI will have high urine OAT1, OAT3 and OAT4.

High NaCl-induced activation of CDK5 increases phosphorylation of the osmoprotective transcription factor TonEBP/OREBP at threonine 135, which contributes to its rapid nuclear localization.

When activated by high NaCl, tonicity-responsive enhancer-binding protein/osmotic response element-binding protein (TonEBP/OREBP) increases transcription of osmoprotective genes. High NaCl activates TonEBP/OREBP by increasing its phosphorylation, nuclear localization, and transactivating activity. In HEK293 cells, mass spectrometry shows phosphorylation of TonEBP/OREBP-S120, -S134, -T135, and -S155. When those residues are individually mutated to alanine, nuclear localization is greater for S155A, less for S134A and T135A, and unchanged for S120A. High osmolality increases phosphorylation at T135 in HEK293 cells and in rat renal inner medullas in vivo. In HEK293 cells, high NaCl activates cyclin-dependent kinase 5 (CDK5), which directly phosphorylates TonEBP/OREBP-T135. Inhibition of CDK5 activity reduces the rapid high NaCl-induced nuclear localization of TonEBP/OREBP but does not affect its transactivating activity. High NaCl induces nuclear localization of TonEBP/OREBP faster (≤2 h) than it increases its overall protein abundance (≥6 h). Inhibition of CDK5 reduces the increase in TonEBP/OREBP transcriptional activity that has occurred by 4 h after NaCl is raised, associated with less nuclear TonEBP/OREBP at that time, but does not reduce either activity or nuclear TonEBP/OREBP after 16 h. Thus high NaCl-induced increase of the overall abundance of TonEBP/OREBP, by itself, eventually raises its effective level in the nucleus, but its rapid CDK5-dependent nuclear localization accelerates the process, speeding transcription of osmoprotective target genes.

Mediator of DNA damage checkpoint 1 (MDC1) contributes to high NaCl-induced activation of the osmoprotective transcription factor TonEBP/OREBP.

BACKGROUND: Hypertonicity, such as induced by high NaCl, increases the activity of the transcription factor TonEBP/OREBP whose target genes increase osmoprotective organic osmolytes and heat shock proteins. METHODOLOGY: We used mass spectrometry to analyze proteins that coimmunoprecipitate with TonEBP/OREBP in order to identify ones that might contribute to its high NaCl-induced activation. PRINCIPAL FINDINGS: We identified 20 unique peptides from Mediator of DNA Damage Checkpoint 1 (MDC1) with high probability. The identification was confirmed by Western analysis. We used small interfering RNA knockdown of MDC1 to characterize its osmotic function. Knocking down MDC1 reduces high NaCl-induced increases in TonEBP/OREBP transcriptional and transactivating activity, but has no significant effect on its nuclear localization. We confirm six previously known phosphorylation sites in MDC1, but do not find evidence that high NaCl increases phosphorylation of MDC1. It is suggestive that MDC1 acts as a DNA damage response protein since hypertonicity reversibly increases DNA breaks, and other DNA damage response proteins, like ATM, also associate with TonEBP/OREBP and contribute to its activation by hypertonicity. CONCLUSIONS/SIGNIFICANCE: MDC1 associates with TonEBP/OREBP and contributes to high NaCl-induced increase of that factor's transcriptional activity.

Phospholipase C-gamma1 is involved in signaling the activation by high NaCl of the osmoprotective transcription factor TonEBP/OREBP.

High NaCl elevates activity of the osmoprotective transcription factor TonEBP/OREBP by increasing its phosphorylation, transactivating activity, and localization to the nucleus. We investigated the possible role in this activation of phospholipase C-gamma1 (PLC-gamma1), which has a predicted binding site at TonEBP/OREBP-phospho-Y143. We find the following. (i) Activation of TonEBP/OREBP transcriptional activity by high NaCl is reduced in PLC-gamma1 null cells and in HEK293 cells in which PLC-gamma1 is knocked down by a specific siRNA. (ii) High NaCl increases phosphorylation of TonEBP/OREBP at Y143. (iii) Wild-type PLC-gamma1 coimmunoprecipitates with wild-type TonEBP/OREBP but not TonEBP/OREBP-Y143A, and the coimmunoprecipitation is increased by high NaCl. (iv) PLC-gamma1 is part of the protein complex that associates with TonEBP/OREBP at its DNA binding site. (v) Knockdown of PLC-gamma1 or overexpression of a PLC-gamma1-SH3 deletion mutant reduces high NaCl-dependent TonEBP/OREBP transactivating activity. (vi) Nuclear localization of PLC-gamma1 is increased by high NaCl. (vii) High NaCl-induced nuclear localization of TonEBP/OREBP is reduced if cells lack PLC-gamma1, if PLC-gamma1 mutated in its SH2C domain is overexpressed, or if Y143 in TonEBP/OREBP is mutated to alanine. (viii) Expression of recombinant PLC-gamma1 restores nuclear localization of wild-type TonEBP/OREBP in PLC-gamma1 null cells but not of TonEBP/OREBP-Y143A. (ix) The PLC-gamma1 phospholipase inhibitor U72133 inhibits nuclear localization of TonEBP/OREBP but not the increase of its transactivating activity. We conclude that, when NaCl is elevated, TonEBP/OREBP becomes phosphorylated at Y143, resulting in binding of PLC-gamma1 to that site, which contributes to TonEBP/OREBP transcriptional activity, transactivating activity, and nuclear localization.

Neuropathy target esterase catalyzes osmoprotective renal synthesis of glycerophosphocholine in response to high NaCl.

Glycerophosphocholine (GPC) is an osmoprotective compatible and counteracting organic osmolyte that accumulates in renal inner medullary cells in response to high NaCl and urea. We previously found that high NaCl increases GPC in renal [Madin-Darby canine kidney (MDCK)] cells. The GPC is derived from phosphatidylcholine, catalyzed by a phospholipase that was not identified at that time. Neuropathy target esterase (NTE) was recently shown to be a phospholipase B that catalyzes production of GPC from phosphatidylcholine. The purpose of the present study was to test whether NTE contributes to the high NaCl-induced increase of GPC synthesis in renal cells. We find that in mouse inner medullary collecting duct cells, high NaCl increases NTE mRNA within 8 h and NTE protein within 16 h. Diisopropyl fluorophosphate, which inhibits NTE esterase activity, reduces GPC accumulation, as does an siRNA that specifically reduces NTE protein abundance. The 20-h half-life of NTE mRNA is unaffected by high NaCl. TonEBP/OREBP is a transcription factor that is activated by high NaCl. Knockdown of TonEBP/OREBP by a specific siRNA inhibits the high NaCl-induced increase of NTE mRNA. Further, the lower renal inner medullary interstitial NaCl concentration that occurs chronically in ClCK1-/- mice and acutely in normal mice given furosemide is associated with lower NTE mRNA and protein. We conclude that high NaCl increases transcription of NTE, likely mediated by TonEBP/OREBP, and that the resultant increase of NTE expression contributes to increased production and accumulation of GPC in mammalian renal cells in tissue culture and in vivo.