Kidney Function Decline and Apparent Treatment-Resistant Hypertension in the Elderly

Background

Cross-sectional studies show a strong association between chronic kidney disease and apparent treatment-resistant hypertension, but the longitudinal association of the rate of kidney function decline with the risk of resistant hypertension is unknown.

Methods

The population-based Three-City included 8,695 participants older than 65 years, 4265 of them treated for hypertension. We estimated the odds ratios (OR) of new-onset apparent treatment-resistant hypertension, defined as blood pressure ≥ 140/90 mmHg despite use of 3 antihypertensive drug classes or ≥ 4 classes regardless of blood pressure, associated with the mean estimated glomerular filtration rate (eGFR) level and its rate of decline over 4 years, compared with both controlled hypertension and uncontrolled nonresistant hypertension with ≤ 2 drugs. GFR was estimated with three different equations.

Results

Baseline prevalence of apparent treatment-resistant hypertension and of controlled and uncontrolled nonresistant hypertension, were 6.5%, 62.3% and 31.2%, respectively. During follow-up, 162 participants developed apparent treatment-resistant hypertension. Mean eGFR decline with the MDRD equation was 1.5±2.9 mL/min/1.73 m² per year: 27.7% of the participants had an eGFR ≥3 and 10.1% ≥ 5 mL/min/1.73 m² per year. After adjusting for age, sex, obesity, diabetes, and cardiovascular history, the ORs for new-onset apparent treatment-resistant hypertension associated with a mean eGFR level, per 15 mL/min/1.73m² drop, were 1.23 [95% confidence interval 0.91–1.64] compared to controlled hypertension and 1.10 [0.83–1.45] compared to uncontrolled nonresistant hypertension; ORs associated with a decline rate ≥ 3 mL/min/1.73m² per year were 1.89 [1.09–3.29] and 1.99 [1.19–3.35], respectively. Similar results were obtained when we estimated GFR with the CKDEPI and the BIS1 equations. ORs tended to be higher for an eGFR decline rate ≥ 5 mL/min/1.73m² per year.

Conclusion

The speed of kidney function decline is associated more strongly than kidney function itself with the risk of apparent treatment-resistant hypertension in the elderly.     

Some characteristics of TRH-induced grooming behavior in rats

Intracerebroventricular administration of TRH induces excessive grooming behavior that is characterized by an important contribution of the elements scratching and paw licking. As compared with other grooming inducing peptides, the pattern of TRH-induced grooming resembles that induced by beta-endorphin rather than those elicited by ACTH or bombesin. TRH-induced excessive grooming is suppressed by pretreatment with haloperidol, naloxone or neurotensin. Haloperidol suppresses TRH-induced grooming in a general way, whereas the suppressive effect of the other drugs is mainly due to a selective reduction of TRH-induced excessive scratching. Combined treatments of rats with TRH and a submaximal dose of ACTH, bombesin or beta-endorphin do not result in higher grooming scores than with single peptide treatment. Excessive grooming elicited by water immersion is not affected by TRH. It is concluded that TRH is undoubtedly an excessive grooming inducing peptide. In situations where excessive grooming is elicited by other peptides or by water immersion, TRH does not further activate the operating systems involved in the existing excessive grooming.     

Interaction between the unphosphorylated receptor with high affinity for IgE and Lyn kinase

Chinese hamster ovary fibroblasts previously transfected with the high affinity receptor for IgE (FcepsilonRI) were further transfected with the alpha subunit of the receptor for interleukin 2 (Tac) or with chimeric constructs in which the cytoplasmic domain of Tac was replaced with the C-terminal cytoplasmic domain of either the beta subunit or the gamma subunit of FcepsilonRI. Whereas native Tac failed to affect the aggregation-induced phosphorylation of FcepsilonRI, both chimeric constructs substantially inhibited this reaction. Alternatively, the FcepsilonRI-bearing fibroblasts were transfected with two chimeric constructs in which the cytoplasmic domain of Tac was replaced with a modified short form of Lyn kinase. The Lyn in both of the chimeric constructs had been mutated to remove the sites that are normally myristoylated and palmitoylated, respectively; one of the constructs had in addition been altered to be catalytically inactive. The catalytically active construct enhanced, and the inactive construct inhibited, aggregation-induced phosphorylation of the receptors. All of the chimeric constructs were largely distributed outside the detergent resistant microdomains, and whereas aggregation caused them to move to the domains in part, their aggregation was neither necessary nor enhanced their effects. These results and others indicate that the receptor and Lyn interact through protein-protein interactions that neither are dependent upon either the post-translational modification of the kinase with lipid moieties nor result exclusively from their co-localization in specialized membrane domains.     

IgA immunodeficiency leads to inadequate Th cell priming and increased susceptibility to influenza virus infection

IgA is considered to be the principal Ab involved in defense against pathogens in the mucosal compartment. Using mice with a targeted disruption in IgA gene expression (IgA(-/-) mice), we have examined the precise role of IgA in protective anti-influenza responses after intranasal vaccination. IgA(-/-) mice immunized intranasally with soluble hemagglutinin (hemagglutinin subtype 1) and neuraminidase (neuraminidase subtype 1) vaccine in the absence of adjuvant were found to be more susceptible to influenza virus infection than IgA(+/+) mice (13 vs 75% survival after virus challenge). Inclusion of IL-12 during immunization restored the protective efficacy of the vaccine to that seen in IgA(+/+) animals. IgA(-/-) mice had no detectable IgA expression, but displayed enhanced serum and pulmonary IgM and IgG Ab levels after IL-12 treatment. Assessment of T cell function revealed markedly depressed splenic lymphoproliferative responses to PHA in IgA(-/-) animals compared with IgA(+/+) mice. Furthermore, IgA(-/-) animals displayed impaired T cell priming to the H1N1 subunit vaccine, with concomitant reduction in recall memory responses due to a defect in APC function. Collectively, these results provide evidence that a major role of IgA is to facilitate presentation of Ag to mucosal T cells. IL-12 treatment can overcome IgA deficiency by providing adequate T cell priming during vaccination.     

Fc receptor-mediated phagocytosis makes a significant contribution to clearance of influenza virus infections

Fc receptors for IgG expressed on macrophages and NK cells are important mediators of opsonophagocytosis and Ab-dependent cell-mediated cytotoxicity. Phagocyte-mediated opsonophagocytosis is pivotal for protection against bacteria, but its importance in recovery from infection with intracellular pathogens is unclear. We have now investigated the role of opsonophagocytosis in protection against lethal influenza virus infection by using FcR gamma(-/-) mice. Absence of the FcR gamma-chain did not affect the expression of IFN-gamma and IL-10 in the lungs and spleens after intranasal immunization with an influenza subunit vaccine. Titers of serum and respiratory Abs of the IgM, IgG1, IgG2a, and IgA isotypes in FcR gamma(-/-) mice were similar to levels seen in FcR gamma(+/+) mice. Nevertheless, FcR gamma(-/-) mice were highly susceptible to influenza infection, even in the presence of anti-influenza Abs from immune FcR gamma(+/+) mice. NK cells were not necessary for the observed Ab-mediated viral clearance, but macrophages were found to be capable of actively ingesting opsonized virus particles. We conclude that Fc receptor-mediated phagocytosis plays a pivotal role in clearance of respiratory virus infections.     

The FLF MADS box gene: a repressor of flowering in Arabidopsis regulated by vernalization and methylation

A MADS box gene, FLF (for FLOWERING LOCUS F ), isolated from a late-flowering, T-DNA-tagged Arabidopsis mutant, is a semidominant gene encoding a repressor of flowering. The FLF gene appears to integrate the vernalization-dependent and autonomous flowering pathways because its expression is regulated by genes in both pathways. The level of FLF mRNA is downregulated by vernalization and by a decrease in genomic DNA methylation, which is consistent with our previous suggestion that vernalization acts to induce flowering through changes in gene activity that are mediated through a reduction in DNA methylation. The flf-1 mutant requires a greater than normal amount of an exogenous gibberellin (GA3) to decrease flowering time compared with the wild type or with vernalization-responsive late-flowering mutants, suggesting that the FLF gene product may block the promotion of flowering by GAs. FLF maps to a region on chromosome 5 near the FLOWERING LOCUS C gene, which is a semidominant repressor of flowering in late-flowering ecotypes of Arabidopsis.     

Direct, convergent hypersensitivity of calcium-activated force generation produced by hypertrophic cardiomyopathy mutant alpha-tropomyosins in adult cardiac myocytes

Familial hypertrophic cardiomyopathy is a clinically and genetically diverse autosomal dominant disorder characterized by ventricular hypertrophy and myocyte disarray in the absence of known hypertrophic stimuli. It has been linked to many cardiac contractile proteins, including four point mutations in alpha-tropomyosin (Tm). Here we use adenoviral-mediated gene transfer into adult cardiac myocytes in vitro to show that all four hypertrophic cardiomyopathy alpha-Tm proteins can be expressed and incorporated into normal sarcomeric structures in cardiac myocytes at similar levels as normal alpha-Tm proteins after 5-6 days in culture. Isometric force recordings of single cardiac myocytes demonstrated inappropriate increased force output at submaximal calcium concentration with a specific mutant allele hierarchy. These data indicate that the severity of direct calcium-sensitizing effect of mutations in alpha-Tm may predict the clinical severity of mutant alpha-Tm-associated hypertrophic cardiomyopathy.     

Altered growth in male peroxisome proliferator-activated receptor gamma (PPARgamma) heterozygous mice: involvement of PPARgamma in a negative feedback regulation of growth hormone action

The peroxisome proliferator-activated receptor gamma (PPARgamma) plays a major role in fat tissue development and physiology. Mutations in the gene encoding this receptor have been associated to disorders in lipid metabolism. A thorough investigation of mice in which one PPARgamma allele has been mutated reveals that male PPARgamma heterozygous (PPARgamma +/-) mice exhibit a reduced body size associated with decreased body weight, reflecting lean mass reduction. This phenotype is reproduced when treating the mice with a PPARgamma- specific antagonist. Monosodium glutamate treatment, which induces weight gain and alters body growth in wild-type mice, further aggravates the growth defect of PPARgamma +/- mice. The levels of circulating GH and that of its downstream effector, IGF-I, are not altered in mutant mice. However, the IGF-I mRNA level is decreased in white adipose tissue (WAT) of PPARgamma +/- mice and is not changed by acute administration of recombinant human GH, suggesting an altered GH action in the mutant animals. Importantly, expression of the gene encoding the suppressor of cytokine signaling-2, which is an essential negative regulator of GH signaling, is strongly increased in the WAT of PPARgamma +/- mice. Although the relationship between the altered GH signaling in WAT and reduced body size remains unclear, our results suggest a novel role of PPARgamma in GH signaling, which might contribute to the metabolic disorder affecting insulin signaling in PPARgamma mutant mice.     

Comparative analysis of parvalbumin and SERCA2a cardiac myocyte gene transfer in a large animal model of diastolic dysfunction

Diastolic dysfunction results from impaired ventricular relaxation and is an important component of human heart failure. Genetic modification of intracellular calcium-handling proteins may hold promise to redress diastolic dysfunction; however, it is unclear whether other important aspects of myocyte function would be compromised by this approach. Accordingly, a large animal model of humanlike diastolic dysfunction was established through 1 yr of left ventricular (LV) pressure overload by descending thoracic aortic coarctation in canines. Serial echocardiography documented a progressive increase in LV mass. Diastolic dysfunction with preserved systolic function was evident at the whole organ and myocyte levels in this model, as determined by hemispheric sonomicrometric piezoelectric crystals, pressure transducer catheterization, and isolated myocyte studies. Gene transfer of the sarco(endo)plasmic reticulum calcium-ATPase (SERCA2a) and parvalbumin (Parv), a fast-twitch skeletal muscle Ca(2+) buffer, restored cardiac myocyte relaxation in a dose-dependent manner under baseline conditions. At high Parv concentrations, sarcomere shortening was depressed. In contrast, during beta-adrenergic stimulation, the expected enhancement of myocyte contraction (inotropy) was abrogated by SERCA2a but not by Parv. The mechanism of this effect is unknown, but it could relate to the uncoupling of SERCA2a/phospholamban in SERCA2a myocytes. Considering that inotropy is vital to overall cardiac performance, the divergent effects of SERCA2a and Parv reported here could impact potential therapeutic strategies for human heart failure.