Shih Hua Lin

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.

Mechanism of regulation of renal ion transport by WNK kinases.

Purpose of reviewThis review summarizes recent advances in the understanding of the mechanism of regulation of renal ion transport by WNK kinases. Recent findingsThere are four mammalian WNK (with-no-lysine [K]) kinases: WNK1–WNK4. Mutations of WNK1 and WNK4 in humans cause hypertension and hyperkalemia at least partly by altering renal sodium and potassium transport. WNK1 and WNK4 stimulate endocytosis of ROMK1 by recruiting an endocytic scaffold protein, intersectin. The recruitment is independent of the kinase activity and occurs between the PXXP motif of WNKs and the SH3 domain of intersectin. Regulation of cation-chloride-coupled cotransporters, Na+–K+–2Cl− cotransporter (NKCC) 1 and NKCC2 [and the Na–Cl co-transporter (NCC), under some conditions] by WNKs requires kinase activity. WNK1 and WNK4 bind with and phosphorylate two Ste20-related protein kinases, OSR1 and SPAK, which in turn bind with and phosphorylate NKCCs and NCC to increase their activity. Binding of OSR1/SPAK to upstream activators (WNKs) and downstream substrates (NKCCs and NCC) are both mediated by a docking site in the C-terminus of OSR1/SPAK and RFX[V/I] motifs present in WNKs or in NKCCs and NCC. SummaryWNKs regulate ion transport via both catalytic and noncatalytic mechanisms. We discuss hypotheses that WNKs, contrasting with aldosterone, play important roles in dissociating sodium reabsorption from potassium secretion.

Electrocardiographic Manifestations in Patients with Thyrotoxic Periodic Paralysis

Background: Thyrotoxic periodic paralysis (TPP) commonly precedes the overt symptoms and signs of hyperthyroidism and may be misdiagnosed as other causes of paralysis (non‐TPP). Because the cardiovascular system is very sensitive to elevation of thyroid hormone, we hypothesize that electrocardiographic manifestations may aid in early diagnosis of TPP. Methods: We retrospectively identified 54 patients who presented to the emergency department (ED) with hypokalemic paralysis during a 3.5‐year period. Thirty‐one patients had TPP and 23 patients had non‐TPP, including sporadic periodic paralysis, distal renal tubular acidosis, diuretic use, licorice intoxication, primary hyperaldosteronism, and Bartter‐like syndrome. Electrocardiograms during attacks were analyzed for rate, rhythm, conduction, PR interval, QRS voltage, ST segment, QT interval, U waves, and T waves. Results: There were no significant differences in age, sex distribution, and plasma K+ concentration between the TPP and non‐TPP groups. Plasma phosphate was significantly lower in TPP than non‐TPP. Heart rate, PR interval, and QRS voltage were significantly higher in TPP than non‐TPP. Forty‐five percent of TPP patients had first‐degree atrioventricular block compared with 13% in the non‐TPP group. There were no significant differences in QT shortening, ST depression, U wave appearance, or T wave flattening between the 2 groups. Conclusion: Relatively rapid heart rate, high QRS voltage, and first‐degree AV block are important clues suggesting TPP in patients who present with hypokalemia and paralysis.

Mechanism of Thyrotoxic Periodic Paralysis

The pathogenesis of thyrotoxic periodic paralysis has long been thought related to increased Na(+)-K(+) ATPase activity stimulated by thyroid hormone and/or hyperadrenergic activity and hyperinsulinemia. This mechanism alone, however, cannot adequately explain how hypokalemia occurs during acute attacks or the associated paradoxical depolarization of the resting membrane potential. Recent findings that loss of function mutations of the skeletal muscle-specific inward rectifying K(+) (Kir) channel, Kir2.6, associate with thyrotoxic periodic paralysis provide new insights into how reduced outward K(+) efflux in skeletal muscle, from either channel mutations or inhibition by hormones (adrenalin or insulin), can lead to a vicious cycle of hypokalemia and paradoxical depolarization, which in turn, inactivates Na(+) channels and causes muscle unexcitability and paralysis.

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.

Identification and Functional Characterization of Kir2.6 Mutations Associated with Non-familial Hypokalemic Periodic Paralysis

Hypokalemic periodic paralysis (hypoKPP) is characterized by episodic flaccid paralysis of muscle and acute hypokalemia during attacks. Familial forms of hypoKPP are predominantly caused by mutations of either voltage-gated Ca2+ or Na+ channels. The pathogenic gene mutation in non-familial hypoKPP, consisting mainly of thyrotoxic periodic paralysis (TPP) and sporadic periodic paralysis (SPP), is largely unknown. Recently, mutations in KCNJ18, which encodes a skeletal muscle-specific inwardly rectifying K+ channel Kir2.6, were reported in some TPP patients. Whether mutations of Kir2.6 occur in other patients with non-familial hypoKPP and how mutations of the channel predispose patients to paralysis are unknown. Here, we report one conserved heterozygous mutation in KCNJ18 in two TPP patients and two separate heterozygous mutations in two SPP patients. These mutations result in V168M, R43C, and A200P amino acid substitution of Kir2.6, respectively. Compared with the wild type channel, whole-cell currents of R43C and V168M mutants were reduced by ∼78 and 43%, respectively. No current was detected for the A200P mutant. Single channel conductance and open probability were reduced for R43C and V168M, respectively. Biotinylation assays showed reduced cell surface abundance for R43C and A200P. All three mutants exerted dominant negative inhibition on wild type Kir2.6 as well as wild type Kir2.1, another Kir channel expressed in the skeletal muscle. Thus, mutations of Kir2.6 are associated with SPP as well as TPP. We suggest that decreased outward K+ current from hypofunction of Kir2.6 predisposes the sarcolemma to hypokalemia-induced paradoxical depolarization during attacks, which in turn leads to Na+ channel inactivation and inexcitability of muscles.

A Simple and Rapid Approach to Hypokalemic Paralysis

Hypokalemia with paralysis (HP) is a potentially reversible medical emergency. It is primarily the result of either hypokalemic periodic paralysis (HPP) caused by an enhanced shift of potassium (K(+)) into cells or non-HPP resulting from excessive K(+) loss. Failure to make a distinction between HPP and non-HPP could lead to improper management. The use of spot urine for K(+) excretion rate and evaluation of blood acid-base status could be clinically beneficial in the diagnosis and management. A very low rate of K(+) excretion coupled with the absence of a metabolic acid-base disorder suggests HPP, whereas a high rate of K(+) excretion accompanied by either metabolic alkalosis or metabolic acidosis favors non-HPP. The therapy of HPP requires only small doses of potassium chloride (KCl) to avoid rebound hyperkalemia. In contrast, higher doses of KCl should be administered to replete the large K(+) deficiency in non-HPP.

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.

Diagnosing thyrotoxic periodic paralysis in the ED

Thyrotoxic periodic paralysis (TPP) and sporadic periodic paralysis (SPP) are the most common causes of hypokalemic periodic paralysis (HPP) in EDs in Asia. Their neuromuscular presentations are almost indistinguishable. We conducted this study to identify clinical clues that can help EPs distinguish between TPP and SPP. Thirty-four patients presenting to the ED with HPP were enrolled during a 3-year period. They did not have known hyperthyroidism before the attack and no family history of paralysis. They all had low K(+) excretion rates. Vital signs and blood biochemistry, including acid-base and electrolytes, were measured. TPP was subsequently established by thyroid function tests. Twenty patients had TPP and 14 patients had SPP. There was no significant difference in age and sex distribution between them. Systolic (SBP) but not diastolic blood pressure (SBP 145 +/- 4 vs 128 +/- 4 mm Hg, P < 0.001) and heart rate (106 +/- 3 vs 73 +/- 3 beats/min, P < 0.001) were significantly higher in those experiencing TPP than SPP. Among the biochemical factors, only plasma phosphate concentration (2.2 +/- 0.2 vs 3.2 +/- 0.2 mg/dL, P < 0.001) was significantly lower in those experiencing TPP than SPP. Systolic hypertension, tachycardia, and hypophosphatemia are clinical clues favoring the diagnosis of TPP.

Novel KCNJ5 mutations in sporadic aldosterone-producing adenoma reduce Kir3.4 membrane abundance

CONTEXT Aldosterone-producing adenoma (APA) has been linked to mutations in the KCNJ5 gene encoding the inward-rectifying potassium (K(+)) Kir3.4 channel. These mutations abolish the K(+) selectivity of Kir3.4 and, consequently, cause sodium (Na(+)) leak, depolarized membrane potential, and nonsuppressible aldosterone secretion. OBJECTIVE Our objective was to investigate KCNJ5 mutations in patients with sporadic APA and the role of endogenous Kir3.4 in human adrenocortical cells. DESIGN We screened the KCNJ5 gene from the adrenal adenomas of 69 Chinese patients with sporadic APA and functionally characterized novel Kir3.4 mutations. RESULTS Thirty-seven percent (26 of 69) of our APA patients carried heterozygous somatic mutations in the KCNJ5 gene. Besides the most common G151R and L168R mutations, we identified a previously uncharacterized E145Q mutation and 2 novel mutations (R115W and E246G) in 6 patients. The E145Q mutant conducted a barium-insensitive Na(+)-leak current. The R115W and E246G mutants preserved barium-sensitive, K(+)-selective and Gβγ-activatable Kir3.4 currents, which were ∼30% and ∼15% of wild-type current, respectively. Biotinylation assays revealed markedly reduced membrane abundance of R115W and E246G mutants. All Kir3.4 mutants exerted dominant-negative effects on wild-type channels. Kir3.4 protein expression in APAs with the novel KCNJ5 mutation was significantly lower than those in APAs with wild-type KCNJ5 or Na(+)-leak KCNJ5 mutations. Inhibition of endogenous Kir3.4 by tertiapin-Q significantly depolarized membrane potential and increased CYP11B2 expression in human adrenocortical cells. CONCLUSION Besides Na(+)-leak mutations, novel KCNJ5 mutations causing a reduction of surface and total abundance of Kir3.4 are also associated with sporadic APA. Basal Kir3.4 current is important to maintaining normal resting membrane potential and suppressing aldosterone synthesis in human adrenocortical cells.