Pauling Chu

SPAK-Knockout Mice Manifest Gitelman Syndrome and Impaired Vasoconstriction

Polymorphisms in the gene encoding sterile 20/SPS1-related proline/alanine-rich kinase (SPAK) associate with hypertension susceptibility in humans. SPAK interacts with WNK kinases to regulate the Na(+)-K(+)-2Cl(-) and Na(+)-Cl(-) co-transporters [collectively, N(K)CC]. Mutations in WNK1/4 and N(K)CC can cause changes in BP and dyskalemia in humans, but the physiologic role of SPAK in vivo is unknown. We generated and analyzed SPAK-null mice by targeting disruption of exons 9 and 10 of SPAK. Compared with SPAK(+/+) littermates, SPAK(+/-) mice exhibited hypotension without significant electrolyte abnormalities, and SPAK(-/-) mice not only exhibited hypotension but also recapitulated Gitelman syndrome with hypokalemia, hypomagnesemia, and hypocalciuria. In the kidney tissues of SPAK(-/-) mice, the expression of total and phosphorylated (p-)NCC was markedly decreased, but that of p-OSR1, total NKCC2, and p-NKCC2 was significantly increased. We observed a blunted response to thiazide but normal response to furosemide in SPAK(-/-) mice. In aortic tissues, total NKCC1 expression was increased but p-NKCC1 was decreased in SPAK-deficient mice. Both SPAK(+/-) and SPAK(-/-) mice had impaired responses to the selective α(1)-adrenergic agonist phenylephrine and the NKCC1 inhibitor bumetanide, suggesting that impaired aortic contractility may contribute to the hypotension of SPAK-null mice. In summary, SPAK-null mice have defects of NCC in the kidneys and NKCC1 in the blood vessels, leading to hypotension through renal salt wasting and vasodilation. SPAK may be a promising target for antihypertensive therapy.

Impaired Phosphorylation of Na(+)-K(+)-2cl(-) Cotransporter by Oxidative Stress-Responsive Kinase-1 Deficiency Manifests Hypotension and Bartter- Like Syndrome

Na+-K+-2Cl− cotransporters (NKCCs), including NKCC1 and renal-specific NKCC2, and the Na+-Cl− cotransporter (NCC) play pivotal roles in the regulation of blood pressure (BP) and renal NaCl reabsorption. Oxidative stress-responsive kinase-1 (OSR1) is a known upstream regulator of N(K)CCs. We generated and analyzed global and kidney tubule-specific (KSP) OSR1 KO mice to elucidate the physiological role of OSR1 in vivo, particularly on BP and kidney function. Although global OSR1−/− mice were embryonically lethal, OSR1+/− mice had low BP associated with reduced phosphorylated (p) STE20 (sterile 20)/SPS1-related proline/alanine-rich kinase (SPAK) and p-NKCC1 abundance in aortic tissue and attenuated p-NKCC2 abundance with increased total and p-NCC expression in the kidney. KSP-OSR1−/− mice had normal BP and hypercalciuria and maintained significant hypokalemia on a low-K+ diet. KSP-OSR1−/− mice exhibited impaired Na+ reabsorption in the thick ascending loop on a low-Na+ diet accompanied by remarkably decreased expression of p-NKCC2 and a blunted response to furosemide, an NKCC2 inhibitor. The expression of total SPAK and p-SPAK was significantly increased in parallel to that of total NCC and p-NCC despite unchanged total NKCC2 expression. These results suggest that, globally, OSR1 is involved in the regulation of BP and renal tubular Na+ reabsorption mainly via the activation of NKCC1 and NKCC2. In the kidneys, NKCC2 but not NCC is the main target of OSR1 and the reduced p-NKCC2 in KSP-OSR1−/− mice may lead to a Bartter-like syndrome.

Correlation between histomorphometric parameters of bone resorption and serum type 5b tartrate-resistant acid phosphatase in uremic patients on maintenance hemodialysis

BACKGROUND Serum tartrate-resistant acid phosphatase 5b (TRACP) is a new marker of potential clinical use to monitor osteoclastic activity and bone resorption rate. The relationship between histomorphometric parameters of bone resorption and serum TRACP was evaluated in 14 chronically dialyzed patients and 6 healthy control subjects. METHODS All patients underwent bone biopsies and serum biochemical testing for TRACP, intact parathyroid hormone (iPTH), pyridinoline cross-linked telopeptide domain of type I collagen (ICTP), total calcium, phosphorus, and albumin, which were measured at the time of biopsy. RESULTS Bone histological examination showed predominant hyperparathyroid bone disease (HPT) in 6 patients, mixed uremic osteodystrophy in 3 patients, low-turnover osteomalacia in 1 patient, and adynamic bone disease in 4 patients. Mean TRACP activity was 3.25 +/- 0.59 U/L in control subjects. Median TRACP activity was significantly greater in patients with HPT (11.97 +/- 8.92 U/L) than those with other types of renal osteodystrophy (ROD; 2.17 +/- 0.61 U/L). Serum iPTH levels were greatest in all patients with HPT, but also were significantly elevated in 7 of 8 patients with other types of ROD. Serum ICTP levels also were significantly elevated in all patients with HPT and 6 of 8 patients with other types of ROD. Serum TRACP levels correlated more strongly with histological parameters of osteoclasts than those of erosion. Also, correlations between TRACP and histological parameters of osteoclasts were stronger than those of iPTH and ICTP levels. CONCLUSION These early results suggest that serum TRACP levels correlate well with histological indices of osteoclasts and may serve as a specific marker for osteoclastic activity in patients with renal bone disease.

Role of circulating cytokines and chemokines in exertional heatstroke

ObjectiveThe interplay between inflammatory and anti-inflammatory cytokines, as well as chemokines, has not been well explored in exertional heatstroke. DesignProspective, observational study. PatientsSeventeen military recruits who developed exertional heatstroke and 17 exertional controls who did not develop exertional heatstroke during the same training exercises. SettingUniversity teaching hospital. Measurements and Main ResultsThe severity of exertional heatstroke was evaluated using a Simplified Acute Physiology Score. Plasma cytokines and chemokines were determined using enzyme-linked immunosorbent assay kits. Body temperatures were 41.2 ± 1.2°C and 37.6 ± 0.8°C in exertional heatstroke and exertional controls, respectively. Significantly, plasma cytokines including interleukin (IL)-1&bgr; (3.1 ± 1.6 vs. 1.2 ± 0.8 pg/mL; p < .05), tumor necrosis factor alpha (4.9 ± 4.1 vs. 1.2 ± 2.4 pg/mL; p < .05), IL-6 (15.8 ± 3.2 vs. 1.2 ± 1.2 pg/mL; p < .01), interferon gamma (7.3 ± 4.9 vs. 2.4 ± 4.1 pg/mL; p < .01), IL-2 receptor (1568 ± 643 vs. 610 ± 214 pg/mL; p < .01), IL-4 (2.5 ± 1.2 vs. 1.2 ± 0.8 pg/mL; p < .05), and IL-10 (12.9 ± 9.4 vs. 2.5 ± 4.9 pg/mL; p < .01) and serum chemokines IL-8 (84.2 ± 79.9 vs. 10.4 ± 3.2 pg/mL; p < .01), monocyte chemoattractant protein 1 (959 ± 589 vs. 158 ± 217 pg/mL; p < .01), and RANTES (12464 ± 10505 vs. 5570 ± 2894 pg/mL; p < .01) were elevated in exertional heatstroke compared with exertional controls. Among cytokines, IL-6, interferon gamma, and IL-2 receptor were positively correlated with Simplified Acute Physiology Score (r = .573, p < .01; r = .625, p < .01; and r = .56, p < .05, respectively). Among chemokines, only serum monocyte chemoattractant protein 1 was positively correlated with Simplified Acute Physiology Score (r = .78, p < .001). There was no correlation between either cytokines or chemokines and body temperature. ConclusionsProinflammatory cytokines IL-1&bgr;, tumor necrosis factor alpha, IL-6; T helper 1 cytokines INF-&ggr; and IL-2 receptor; and chemokines IL-8, monocyte chemoattractant protein 1, and RANTES are increased in patients with exertional heatstroke. T helper 2 cytokines may play a role as anti-inflammatory cytokines. IL-6, interferon gamma, IL-2 receptor, and monocyte chemoattractant protein 1 may serve as prognostic indicators of disease severity in exertional heatstroke.

Incidence and factors predictive of acute renal failure in patients with advanced liver cirrhosis

BACKGROUND Acute renal failure (ARF) is a life-threatening entity that frequently complicates advanced liver disease. This study documents a number of factors that may predispose to or precipitate ARF and influence outcomes in patients with advanced liver disease. Comparisons are also made between subgroups of patients with viral and alcohol-induced liver cirrhosis in those with ARF. PATIENTS AND METHODS We conducted a retrospective chart review over one year of 127 consecutive hospital admissions in 82 patients who were diagnosed with advanced liver cirrhosis (Child-Pugh Class C) in a tertiary care center. A diagnosis of ARF was made in 29 admissions and another 98 admissions not complicated by ARF served as controls. This study evaluated different etiologies of ARF and developed a database which included clinical features, biochemical parameters, the etiology of cirrhosis, possible predisposing factors, and precipitating events. Version II of the Acute Physiology and Chronic Health Physiology Scoring system (APACHE II) was applied to predict short-term hospital mortality rates. RESULTS ARF occurred in 29 admissions over the one-year study period (23%). The mean age of these patients was 56.8 +/- 12.0 years, and 73% were men. The patients with ARF had significant hyponatremia and higher levels of serum bilirubin, aspartate aminotransferase (AST), alanine aminotransferase (ALT), and white cell counts on admission than the controls. Patients who developed ARF were more likely to have had infection, especially septicemia, and gastrointestinal (GI) bleeding. Mortality rate in the patients with ARF was much higher than in those patients without ARF (72% vs. 13%, p < 0.001). The patients with viral cirrhosis and ARF were found to have higher leukocyte counts, serum bilirubin levels, and more frequent incidence of infection, septicemia and GI bleeding compared to the patients with alcoholic liver cirrhosis and ARF. Those with viral hepatitis were also significantly older and had more frequent incidence of ascites, but had lower levels of gamma-glutamyl transpeptidase and less frequent incidence of encephalopathy. CONCLUSIONS The risk of ARF is significantly increased in patients with advanced liver cirrhosis presenting with marked hyperbilirubinemia, hyponatremia, elevated liver enzymes, infection, and GI bleeding. The presence of ARF leads to higher mortality rates in both viral and alcohol-induced liver cirrhosis.

Aberrant cytokines/chemokines production correlate with proteinuria in patients with overt diabetic nephropathy

BACKGROUND Diabetic nephropathy (DN) occurs in 20% to 30% of all patients with type 2 diabetes mellitus (DM) and is the most common cause of end-stage renal disease. However, the definite pathogenesis, especially the role of immune response, is still unclear. METHODS We studied the production and expression of Th1 (IFN-gamma, IL-2R), Th2 (IL-4, IL-10), proinflammatory cytokines (IL-1beta, and TNF-alpha), and chemokines (MCP-1, and RANTES) in patients with DN. The correlation among cytokines, chemokines, and clinical parameters were examined. RESULTS A patient with DN presented with longer disease duration, heavy proteinuria, and impaired renal function. Our results demonstrated increased proinflammatory cytokines, Th1 cytokines and chemokines, but not Th2 cytokines, in the plasma and urine of patients with DN as compared to patients with DM without overt nephropathy. Enhanced cytokine/chemokine activation in DN was also demonstrated by positive immunohistochemical staining of kidney tissue. We found a positive correlation between daily protein loss and plasma IFN-gamma and IL-2R, and urinary MCP-1, as well as a negative correlation between creatinine clearance and plasma TNF-alpha and urinary MCP-1. CONCLUSIONS There were aberrant cytokines/chemokines production correlated with the degree of proteinuria in patient with overt DN and gross proteinuria. Inflammation may be important in the pathogenesis of DN.

HO-1 induction ameliorates experimental murine membranous nephropathy: anti-oxidative, anti-apoptotic and immunomodulatory effects

BACKGROUND Therapeutic agents for membranous nephropathy (MN) remain ill-defined. Haeme oxygenase (HO)-1 is considered to play a protective role in various disorders. Here, we assessed the efficacy of HO-1 induction therapy for MN. METHODS MN was induced in BALB/c mice with intravenous injections of cationic bovine serum albumin. Three groups of mice were administered 100 micromol/kg Cobalt protoporphyrin (CoPP, a potent HO-1 inducer), Tin protoporphyrin (SnPP, a potent HO-1 inhibitor) or phosphate-buffered saline via intra-peritoneal injections once a week starting from the induction of MN. Disease severity was verified by serum and urine metabolic profiles and by renal histopathology. Cytokine profiles, immunoglobulin production, the expression of oxidative stress markers (thiobarbituric acid reactive substances, TBARS) and apoptosis, as measured by TUNEL, were also determined. RESULTS Mice treated with CoPP displayed a significant reduction in proteinuria and a marked amelioration of glomerular lesions, accompanied by attenuated immune-complex deposition. The production of immunoglobulins in MN mice treated with CoPP was significantly reduced compared with that of mice in the other two groups. TBARS in the serum and kidneys, as well as apoptosis, were also significantly reduced in CoPP-treated mice. Cytokine mRNA expression in the renal cortex indicated that CoPP not only decreased the expression of proinflammatory cytokines, but also increased the expression of anti-inflammatory cytokines (interleukin-10). CONCLUSIONS HO-1 induction therapy may ameliorate experimental MN via multiple pathways, including anti-oxidative, anti-apoptotic and immunomodulatory effects. HO-1 inducing regimens should be considered as a potential therapeutic intervention in MN in the future.

Early diagnosis of thyrotoxic periodic paralysis: spot urine calcium to phosphate ratio.

Objectives:To identify a clinically reliable index of thyrotoxic periodic paralysis (TPP), a life-threatening emergency with unique and effective therapies. Design:Diagnostic study. Setting:University teaching hospital. Patients:Fifty-three consecutive patients with hypokalemic paralysis during a 3-yr period and 30 thyrotoxic patients without paralysis as the thyrotoxic control group. Interventions:For patients with hypokalemic paralysis, blood and second-void spot urine samples were obtained and measured by routine laboratory prior to therapy. For the thyrotoxic control group, blood and spot urine were collected when they visited outpatient clinics. Measurements and Main Results:Twenty-nine patients fulfilled the criteria for TPP. Compared with the thyrotoxic control group, the TPP group had significant decreases in plasma potassium (K+) and phosphate concentrations associated with very low urine K+ and phosphate excretion. Compared with the non-TPP group, the TPP group had significantly lower plasma creatinine and phosphate levels, a significantly higher urine calcium to creatinine ratio (0.25 ± 0.12 vs. 0.08 ± 0.07 mg/mg, p < .001), and a significantly lower urine phosphate to creatinine ratio (0.08 ± 0.05 vs. 0.31 ± 0.23 mg/mg, p < .001). The urine calcium to phosphate ratio had greater discriminatory power between TPP and non-TPP hypokalemic paralysis (4.1 ± 2.3 vs. 0.5 ± 0.6 mg/mg, p < .001). Using a urine calcium to phosphate ratio cutoff value of 1.7 mg/mg, sensitivity and specificity for TPP were 100% and 96%, respectively. Conclusions:Hypercalciuria and hypophosphaturia are characteristic features of TPP.

Melatonin enhances endogenous heme oxygenase-1 and represses immune responses to ameliorate experimental murine membranous nephropathy.

Abstract:  Idiopathic membranous nephropathy (MN), an autoimmune‐mediated glomerulonephritis, is one of the most common causes of nephrotic syndrome in adults. Therapeutic agents for MN remain ill defined. We assessed the efficacy of melatonin therapy for MN. Experimental murine MN was induced with cationic bovine serum albumin, and the mice were immediately administered 20 mg/kg melatonin or phosphate‐buffered saline subcutaneously once a day. Disease severity was verified by examining serum and urine metabolic profiles and renal histopathology. The expression of cytokines and oxidative stress markers, cell apoptosis, and the associated mechanisms were also determined. Mice treated with melatonin displayed a significant reduction in proteinuria and a marked amelioration of glomerular lesions, with attenuated immunocomplex deposition. The subpopulations of T cells were not altered, but the CD19+ B‐cell subpopulation was significantly reduced in the MN mice treated with melatonin. The expression of cytokine mRNAs in splenocytes indicated that melatonin reduced the expression of proinflammatory cytokines and increased the expression of anti‐inflammatory cytokines (interleukin 10). The production of reactive oxygen species and TUNEL‐positive apoptotic cells in the kidney were also significantly reduced in the melatonin‐treated MN mice. Melatonin also upregulated heme oxygenase 1 (HO1) and ameliorated MN. The blockade of HO1 expression with SnPP, a HO1 inhibitor, attenuated HO1 induction by melatonin and thus mitigated its renoprotective effects during MN. Our results suggest that melatonin treatment ameliorates experimental MN via multiple pathways, including by its antioxidative, antiapoptotic, and immunomodulatory effects. Melatonin should be considered a potential therapeutic intervention for MN in the future.

Increased nitric oxide production in hypotensive hemodialysis patients

A subset of patients on long-term hemodialysis have sustained hypotension, defined as a predialysis systolic pressure of < 100 mmHg. To determine the role of nitric oxide (NO), an important vasodilator, in this condition, the authors measured the plasma levels of nitrite (NO2-) and nitrate (NO3-), the known NO metabolites taken as an index of NO production, in 10 hypotensive patients on long-term hemodialysis. None of them had diabetes, cirrhosis of the liver, congestive heart failure, or infection. Fifteen age and gender-matched normotensive patients on hemodialysis were selected as control subjects. Measurements of plasma levels of nitrite and nitrate based on the Greiss reaction were made. There was no significant difference in hematocrit, serum intact parathyroid hormone, total calcium, inorganic phosphorus, albumin, heart rate, cardiac index, or interdialysis weight gain between these two groups. Plasma nitrite and nitrate levels did not correlate with either predialysis serum creatinine or blood urea nitrogen. The mean arterial pressure (MAP) was significantly lower and plasma nitrite and nitrate levels were significantly higher in chronic hypotensive patients than in normotensive patients (MAP: 68.30 +/- 3.24 mmHg vs 95.20 +/- 2.44 mmHg, p < 0.001; plasma nitrite and nitrate: 72.49 +/- 14.41 mumol/L vs 36.42 +/- 5.45 mumol/L, p < 0.05). In addition, MAP from hypotensive and normotensive patients on hemodialysis was inversely correlated with plasma levels of nitrite and nitrate (r = -0.54, p < 0.01). It was concluded that enhanced NO production in this subset of patients on hemodialysis may contribute to their chronic hypotension.