Differential effects of eplerenone versus amlodipine on muscle metaboreflex function in hypertensive humans

Numerous studies have demonstrated that sympathetic nervous system overactivation during exercise in hypertensive rodents and humans is due, in part, to an exaggerated reflex response known as the exercise pressor reflex. Our prior studies have implicated a key role of mineralocorticoid receptor activation in mediating an augmented exercise pressor reflex in spontaneously hypertensive rats, which is mitigated by blockade with eplerenone. However, the effect of eplerenone on exercise pressor reflex has not been assessed in human hypertension. Accordingly, the authors performed a randomized crossover study to compare the effects of eplerenone to another antihypertensive drug from a different class amlodipine on sympathetic nerve activity (SNA) in 14 patients with uncomplicated hypertension. The authors found that amlodipine unexpectedly augmented the increase in SNA during the second minute of isometric handgrip, which persisted into the post‐exercise circulatory arrest period (∆ SNA, from rest of 15 ± 2 vs. 9 ± 2 vs. 10 ± 2 bursts/min, amlodipine vs. baseline vs. eplerenone, respectively, p < .01), suggesting an exaggerated muscle metaboreflex function. Eplerenone did not alter sympathetic responses to exercise or post‐exercise circulatory arrest in the same hypertensive individuals. In conclusions, our studies provide the first direct evidence for a potentially unfavorable potentiation of muscle metaboreflex by amlodipine during isometric handgrip exercise in hypertensive patients whereas eplerenone has no significant effect. Our study may have clinical implications in terms of selection of antihypertensive agents that have the least detrimental effects on sympathetic neural responses to isometric exercise.     

Ophiophagus hannah Venom: Proteome,Components Bound by Naja kaouthia Antivenin and Neutralization by N. kaouthia Neurotoxin-Specific Human ScFv

Venomous snakebites are an important health problem in tropical and subtropical countries. King cobra (Ophiophagus hannah) is the largest venomous snake found in South and Southeast Asia. In this study, the O. hannah venom proteome and the venom components cross-reactive to N. kaouthia monospecific antivenin were studied. O. hannah venom consisted of 14 different protein families, including three finger toxins, phospholipases, cysteine-rich secretory proteins, cobra venom factor, muscarinic toxin, L-amino acid oxidase, hypothetical proteins, low cysteine protein, phosphodiesterase, proteases, vespryn toxin, Kunitz, growth factor activators and others (coagulation factor, endonuclease, 5’-nucleotidase). N. kaouthia antivenin recognized several functionally different O. hannah venom proteins and mediated paratherapeutic efficacy by rescuing the O. hannah envenomed mice from lethality. An engineered human ScFv specific to N. kaouthia long neurotoxin (NkLN-HuScFv) cross-neutralized the O. hannah venom and extricated the O. hannah envenomed mice from death in a dose escalation manner. Homology modeling and molecular docking revealed that NkLN-HuScFv interacted with residues in loops 2 and 3 of the neurotoxins of both snake species, which are important for neuronal acetylcholine receptor binding. The data of this study are useful for snakebite treatment when and where the polyspecific antivenin is not available. Because the supply of horse-derived antivenin is limited and the preparation may cause some adverse effects in recipients, a cocktail of recombinant human ScFvs for various toxic venom components shared by different venomous snakes, exemplified by the in vitro produced NkLN-HuScFv in this study, should contribute to a possible future route for an improved alternative to the antivenins.     

Association of CTXN3-SLC12A2 polymorphisms and schizophrenia in a Thai population

Background

A genome-wide association study (GWAS) combined with brain imaging as a quantitative trait analysis revealed that the SNPs near CTXN3-SLC12A2 region were related to forebrain development and stress response which involved in schizophrenia. In the present study, the SNPs in this region were analyzed for association with schizophrenia in a Thai population.

Methods

A total of 115 schizophrenia and 173 unrelated normal controls with mean age of 37.87?±?11.8 and 42.81?±?6.0?years, respectively, were included in this study. Genotyping was performed using polymerase chain reaction and high-resolution melting (HRM) analysis. The difference in genotype distribution between patient and control was assessed by Chi-square test of the SPSS software.

Results

We found a significant association between the GWAS-discovered SNP, rs245178, with the risk of schizophrenia in the Thai population [P?=?0.006, odds ratio for the minor G allele: 0.62(0.46?C0.83)]. Additionally, another potential SNP, rs698172, which was in moderate linkage disequilibrium with rs245178, also showed strong association with schizophrenia [P?=?0.003, odds ratio for minor T allele: 0.61(0.46?C0.82)]. This association remained significant at 5% level after the Bonferroni correction for multiple testing.

Conclusions

This study shows that two SNPs in intergenic of the CTXN3 and SLC12A2 genes, rs245178 and rs698172, are associated with risk of schizophrenia in Thai population. Further study is required for clarification the role of genetic variation around these SNPs in expression pattern of the CTXN3 and SLC12A2 genes, which may be involved in schizophrenia pathogenesis.     

Estrogen and hypertension

Menopause is accompanied by a dramatic rise in the prevalence of hypertension in women, suggesting a protective role of endogenous estradiol on blood pressure (BP). Both animal experimental and human clinical investigations suggest that estrogen engages several mechanisms that protect against hypertension, such as activation of the vasodilator pathway mediated by nitric oxide and prostacyclin and inhibition of the vasoconstrictor pathway mediated by the sympathetic nervous system and angiotensin. However, emerging evidence from recent clinical trials indicates a small increase, rather than decrease, in systolic BP with oral estrogen administration in postmenopausal women, without any detectable effect on diastolic BP. Mechanisms underlying this selective rise in systolic BP in postmenopausal women and oral contraceptive-induced hypertension in premenopausal women remain unknown, but the rise may be related to supraphysiologic concentration of estrogen in the liver. To date, transdermal delivery of estrogen, which avoids the first-pass hepatic metabolism of estradiol, appears to have a small BP-lowering effect in postmenopausal women and may be a safer alternative in hypertensive women.     

Epitope mapping of monoclonal antibodies specific to serovar of Leptospira, using phage display technique

Random heptapeptide library displayed by bacteriophage T7 was used to characterize epitopes of five monoclonal antibodies that were specific to L. australis, L. bangkok, and L. bratislava. Phages selected by biopanning were cloned by plaque isolation, and the binding specificity of individual clones was confirmed by enzyme-linked immunosorbent assay, before being further amplified and checked for phage peptide sequence using PCR and DNA sequencing. Almost all of the peptide epitopes were continuous or linear. Interestingly, in phages reacting with the monoclonal antibody (MAb) clones F11, F20, 2C3D4, and 8C6C4A12, the deduced amino acid sequence of the displayed peptides corresponded to a segment of hypothetical protein of the Leptospira genome (L. interrogans serovar Lai and Copenhageni). Considering the deduced amino acid sequences of phages reacting with the MAb clones F11, F20, 2C3D4, and 8C6C4A12, the consensus motif -SKSSRC-, -TLINIF-, -SSKSYR- and -CTPKKSGRC- appeared respectively. No similarity was observed among phage reacting with the MAb clone F21. The results demonstrate that T7 phage display technique has potential for epitope mapping of leptospiral MAbs, and for rapid analysis of the interactions between phage display peptides with the MAb. The finding of a phage peptide that binds to MAb with protective activity can be further tested as a candidate for leptospirosis vaccine in the future.     

Differential effects of oral versus transdermal estrogen replacement therapy on C-reactive protein in postmenopausal women

OBJECTIVES: We investigated whether the route of estrogen replacement therapy (ET) is the major determinant of C-reactive protein (CRP) in postmenopausal women. BACKGROUND: Recent studies demonstrated that oral ET causes a sustained increase in CRP, implicating a proinflammatory effect. Because CRP is synthesized in the liver, we hypothesized that estrogen-induced CRP elevation is related to first-pass hepatic metabolism. METHODS: In 21 postmenopausal women, we conducted a randomized, crossover, placebo-controlled study to compare the effects of transdermal versus oral ET on CRP and inflammatory cytokines. We measured CRP, interleukin (IL)-1-beta, IL-6, and tumor necrosis factor-alpha before and after eight weeks of transdermal estradiol (E(2)) (100 microg/day), oral conjugated estrogen (CEE) (0.625 mg/day), or placebo. Insulin-like growth factor-1 (IGF-1), a hepatic-derived anabolic peptide, was also measured. RESULTS: Transdermal E(2) had no effect on CRP or IGF-1 levels. In contrast, eight weeks of oral conjugated estrogens caused a more than twofold increase in CRP and a significant reduction in IGF-1 (p < 0.01) in the same women. The magnitude of increase in CRP was inversely correlated to the decrease in IGF-1 (r = -0.49, p = 0.008). Neither transdermal E(2) nor oral CEE had any effects on the plasma concentrations of cytokines that promote CRP synthesis. CONCLUSIONS: In postmenopausal women, oral but not transdermal ET increased CRP by a first-pass hepatic effect. An increase in CRP levels is accompanied by a reduction in IGF-1, an anti-inflammatory growth factor. Because CRP is a powerful predictor of an adverse prognosis in otherwise healthy postmenopausal women, the route of administration may be an important consideration in minimizing the adverse effects of ET on cardiovascular outcomes.     

C-Reactive Protein Causes Insulin Resistance in Mice Through Fcγ Receptor IIB–Mediated Inhibition of Skeletal Muscle Glucose Delivery

Elevations in C-reactive protein (CRP) are associated with an increased risk of insulin resistance. Whether CRP plays a causal role is unknown. Here we show that CRP transgenic mice and wild-type mice administered recombinant CRP are insulin resistant. Mice lacking the inhibitory Fcγ receptor IIB (FcγRIIB) are protected from CRP-induced insulin resistance, and immunohistochemistry reveals that FcγRIIB is expressed in skeletal muscle microvascular endothelium and is absent in skeletal muscle myocytes, adipocytes, and hepatocytes. The primary mechanism in glucose homeostasis disrupted by CRP is skeletal muscle glucose delivery, and CRP attenuates insulin-induced skeletal muscle blood flow. CRP does not impair skeletal muscle glucose delivery in FcγRIIB^−/− mice or in endothelial nitric oxide synthase knock-in mice with phosphomimetic modification of Ser1176, which is normally phosphorylated by insulin signaling to stimulate nitric oxide–mediated skeletal muscle blood flow and glucose delivery and is dephosphorylated by CRP/FcγRIIB. Thus, CRP causes insulin resistance in mice through FcγRIIB-mediated inhibition of skeletal muscle glucose delivery.Numerous clinical studies indicate that chronic, mild increases in circulating levels of the acute-phase reactant C-reactive protein (CRP) are associated with insulin resistance (1–5). For example, in middle-aged men, independent of numerous risk factors including baseline BMI, individuals in the top quintile of CRP (>4.18 μg/mL) had a more than threefold greater risk of developing diabetes than those in the lowest quintile (<0.66 μg/mL) (6). However, the relationship between CRP and type 2 diabetes has been greatly debated (7–10), and whether CRP plays a pathogenetic role is unknown.In the current study, we determined how CRP influences glucose homeostasis in vivo, testing the hypothesis that CRP induces insulin resistance in mice. Additional studies were performed to address the following questions:

• Which regulatory processes in glucose homeostasis are altered by CRP?
• Is the effect of CRP on glucose homeostasis mediated by Fcγ receptors (FcγR) for IgG, which bind CRP to invoke its cellular actions in certain paradigms (11,12)?
• How does CRP action via FcγR cause insulin resistance?

     

Specific monoclonal antibodies to Strongyloides stercoralis: a potential diagnostic reagent for strongyloidiasis

In this study, specific hybridomas secreting monoclonal antibodies (MAb) to antigen of Strongyloides stercoralis filariform larvae were produced. Specific epitopes targeted by the MAb were protein in nature and located in situ in the internal content of the filariform larvae of the parasite but not in the esophagus. The MAb reacted to the homologous antigen in an indirect ELISA but did not reveal any reaction to the SDS-PAGE separated-homologous antigen in a Western blot analysis (WB) suggesting a conformational epitope specificity. The MAb were of IgG1 isotype which is the isotype known to have high affinity to this epitope so they were used in a dot-ELISA to detect the antigen of the parasite. The assay could detect the epitopes in 78 ng or more of the crude filariform larval extract but did not reveal any positive result when applied to detect antigen in stool samples of parasitologically confirmed strongyloidiasis patients. The negative antigen test results can be explained as follows. Either the MAb were filariform stage-specific and thus did not recognize the rhabditiform larval antigen mainly contained in the patient's stool or the amounts of antigen in the stool samples were too small and/or unevenly dispersed. In the latter instance, the MAb developed in this study would have a diagnostic potential if used in an immunological test design where more volume of fresh stool sample could be accommodated in the test, e.g. a sandwich plate ELISA.     

Salsolinol, a dopamine-derived tetrahydroisoquinoline, induces cell death by causing oxidative stress in dopaminergic SH-SY5Y cells, and the said effect is attenuated by metallothionein

The endogenous neurotoxin, 1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline (salsolinol), has been considered a potential neurotoxin in the etiology of Parkinson's disease (PD). Salsolinol and N-methyl(R)-salsolinol were identified in the brains and cerebrospinal fluid (CSF) of PD patients. Oxidative stress is known to be one of the major contributing factors in the cascade that may finally leads to the cell death in PD. The present study was undertaken to understand the role of salsolinol in oxidative-mediated neuronal toxicity in dopaminergic SH-SY5Y cells, and the neuroprotective effects of metallothionein (MT) against salsolinol toxicity in MT overexpressing (MT(trans)) fetal mesencephalic cells. Salsolinol increased the production of reactive oxygen species (ROS) and significantly decreased glutathione (GSH) levels and cell viability in SH-SY5Y cells. Salsolinol also decreased intracellular ATP levels and induced nuclear condensation in these cells. Salsolinol-induced depletion in cell viability was completely prevented by N-acetylcysteine in SH-SY5Y cells, and also prevented by MT in MT(trans) fetal mesencephalic cells compared to control(wt) cells. The extent of nuclear condensation and caspase activation was also less in MT(trans) cells than control(wt) cells. These results suggest that salsolinol causes oxidative stress by decreasing the levels of GSH and by increasing ROS production, and these events may lead to the death of dopaminergic cell. Furthermore, MT overexpression may protect dopaminergic neurons against salsolinol-induced neurotoxicity, most probably by the inhibition of oxidative stress and apoptotic pathways including caspase-3 activation.