Exposure to sodium butyrate leads to functional downregulation of calcium-activated potassium channels in human airway epithelial cells

Aging as a loss of morphostatic information: A developmental bioelectricity perspective

Maintaining order at the tissue level is crucial throughout the lifespan, as failure can lead to cancer and an accumulation of molecular and cellular disorders. Perhaps, the most consistent and pervasive result of these failures is aging, which is characterized by the progressive loss of function and decline in the ability to maintain anatomical homeostasis and reproduce. This leads to organ malfunction, diseases, and ultimately death. The traditional understanding of aging is that it is caused by the accumulation of molecular and cellular damage. In this article, we propose a complementary view of aging from the perspective of endogenous bioelectricity which has not yet been integrated into aging research. We propose a view of aging as a morphostasis defect, a loss of biophysical prepattern information, encoding anatomical setpoints used for dynamic tissue and organ homeostasis. We hypothesize that this is specifically driven by abrogation of the endogenous bioelectric signaling that normally harnesses individual cell behaviors toward the creation and upkeep of complex multicellular structures in vivo. Herein, we first describe bioelectricity as the physiological software of life, and then identify and discuss the links between bioelectricity and life extension strategies and age-related diseases. We develop a bridge between aging and regeneration via bioelectric signaling that suggests a research program for healthful longevity via morphoceuticals. Finally, we discuss the broader implications of the homologies between development, aging, cancer and regeneration and how morphoceuticals can be developed for aging.

Epigenetic Metabolite Acetate Inhibits Class I/II Histone Deacetylases, Promotes Histone Acetylation, and Increases HIV-1 Integration in CD4+ T Cells

In this study, we investigated the effect of acetate, the most concentrated short-chain fatty acid (SCFA) in the gut and bloodstream, on the susceptibility of primary human CD4⁺ T cells to HIV-1 infection. We report that HIV-1 replication is increased in CD3/CD28-costimulated CD4⁺ T cells upon acetate treatment. This enhancing effect correlates with increased expression of the early activation marker CD69 and impaired class I/II histone deacetylase (HDAC) activity. In addition, acetate enhances acetylation of histones H3 and H4 and augments HIV-1 integration into the genome of CD4⁺ T cells. Thus, we propose that upon antigen presentation, acetate influences class I/II HDAC activity that transforms condensed chromatin into a more relaxed structure. This event leads to a higher level of viral integration and enhanced HIV-1 production. In line with previous studies showing reactivation of latent HIV-1 by SCFAs, we provide evidence that acetate can also increase the susceptibility of primary human CD4⁺ T cells to productive HIV-1 infection.IMPORTANCE Alterations in the fecal microbiota and intestinal epithelial damage involved in the gastrointestinal disorder associated with HIV-1 infection result in microbial translocation that leads to disease progression and virus-related comorbidities. Indeed, notably via production of short-chain fatty acids, bacteria migrating from the lumen to the intestinal mucosa could influence HIV-1 replication by epigenetic regulatory mechanisms, such as histone acetylation. We demonstrate that acetate enhances virus production in primary human CD4⁺ T cells. Moreover, we report that acetate impairs class I/II histone deacetylase activity and increases integration of HIV-1 DNA into the host genome. Therefore, it can be postulated that bacterial metabolites such as acetate modulate HIV-1-mediated disease progression.

The prostaglandin E₂ type 4 receptor participates in the response to acute oxidant stress in airway epithelial cells

Oxidative stress is implicated in the pathogenesis of many inflammatory pulmonary diseases, including cystic fibrosis (CF). Delineating how oxidative stress stimulates CF transmembrane conductance regulator (CFTR) in airway epithelial cells is useful, both to increase the understanding of airways host defense and suggest therapeutic approaches to reduce the oxidant stress burden in the CF lung. Using the airway epithelial cell line Calu-3, we investigated the hypothesis that hydrogen peroxide (H₂O₂), which stimulates anion efflux through CFTR, does so via the production of prostaglandin E₂ (PGE₂). Using iodide efflux as a biochemical marker of CFTR activity and short circuit current (I(sc)) recordings, we found that the H₂O₂-stimulated efflux was abolished by cyclooxygenase-1 inhibition and potentially also involves microsomal prostaglandin E synthase-1 activity, implicating a role for PGE₂ production. Furthermore, H₂O₂ application resulted in a rapid release of PGE₂ from Calu-3 cells. We additionally hypothesized that the PGE₂ subtype 4 (EP(4)) receptor was involved in mediating this response. In the presence of (4Z)-7-[(rel-1S,2S,5R)-5-((1,1'-biphenyl-4-yl)methoxy)-2-(4-morpholinyl)-3-oxocyclopentyl]-4-heptenoic acid (AH23848) (which blocks the EP₄ receptor), the H₂O₂-stimulated response was abolished. To investigate this finding in a polarized system, we measured the increase in I(sc) induced by H₂O₂ addition in the presence and absence of AH23848. H₂O₂ induced a robust increase in I(sc), which was significantly attenuated in the presence of AH23848, suggesting some role for the EP₄ receptor. In conclusion, with H₂O₂ as a model oxidant stress, stimulation of CFTR seems to involve PGE₂ production and likely EP₄ receptor activation in Calu-3 airway epithelial cells. This mechanism would be compromised in the CF airways.

The intermediate conductance Ca2+-activated K+ channel inhibitor TRAM-34 stimulates proliferation of breast cancer cells via activation of oestrogen receptors

BACKGROUND AND PURPOSE

K(+) channels play a role in the proliferation of cancer cells. We have investigated the effects of specific K(+) channel inhibitors on basal and oestrogen-stimulated proliferation of breast cancer cells.

EXPERIMENTAL APPROACH

Using the mammary adenocarcinoma cell line MCF-7 we assayed cell proliferation by radiolabelled thymidine incorporation in the absence or presence of various K(+) channel inhibitors with or without 17beta-oestradiol.

KEY RESULTS

Inhibitors of K(v)10.1 and K(Ca)3.1 K(+) channels suppressed basal proliferation of MCF-7 cells, but not oestrogen-stimulated proliferation. TRAM-34, a specific inhibitor of K(Ca)3.1 channels increased or decreased cell proliferation depending on the concentration. At intermediate concentrations (3-10 microM) TRAM-34 increased cell proliferation, whereas at higher concentrations (20-100 microM) TRAM-34 decreased cell proliferation. The enhancement of cell proliferation caused by TRAM-34 was blocked by the oestrogen receptor antagonists ICI182,780 and tamoxifen. TRAM-34 also increased progesterone receptor mRNA expression, decreased oestrogen receptor-alpha mRNA expression and reduced the binding of radiolabelled oestrogen to MCF-7 oestrogen receptor, in each case mimicking the effects of 17beta-oestradiol.

CONCLUSIONS AND IMPLICATIONS

Our results demonstrate that K(+) channels K(v)10.1 and K(Ca)3.1 play a role in basal, but not oestrogen-stimulated MCF-7 cell proliferation. TRAM-34, as well as inhibiting K(Ca)3.1, directly interacts with the oestrogen receptor and mimics the effects of 17beta-oestradiol on MCF-7 cell proliferation and gene modulation. Our finding that TRAM-34 is able to activate the oestrogen receptor suggests a novel action of this supposedly specific K(+) channel inhibitor and raises concerns of interpretation in its use.

Activation of the unfolded protein response by deltaF508 CFTR

Environmental insults and misfolded proteins cause endoplasmic reticulum (ER) stress and activate the unfolded protein response (UPR). The UPR decreases endogenous cystic fibrosis transmembrane conductance regulator (CFTR) mRNA levels and protein maturation efficiency. Herein, we investigated the effects of the folding-deficient deltaF508 CFTR on ER stress induction and UPR activation. For these studies, we developed and characterized stable clones of Calu3deltaF cells that express different levels of endogenous wild-type (WT) and recombinant deltaF508 CFTR. We also present a novel RT-PCR-based assay for differential quantification of wild-type CFTR mRNA in the presence of deltaF508 CFTR message. The assay is based on a TaqMan minor groove binding (MGB) probe that recognizes a specific TTT sequence (encoding phenylalanine at position 508 in human CFTR). The MGB probe is extremely specific and sensitive to changes in WT CFTR message levels. In RNA samples that contain both WT and deltaF508 CFTR mRNAs, measurement of WT CFTR mRNA levels (using the MGB probe) and total CFTR mRNA (using commercial primers) allowed us to calculate deltaF508 CFTR mRNA levels. The results indicate that overexpression of deltaF508 CFTR causes ER stress and activates the UPR. UPR activation precedes a marked decrease in endogenous WT CFTR mRNA expression. Furthermore, polarized airway epithelial cell lines are important tools in cystic fibrosis research, and herein we provide an airway epithelial model to study the biogenesis and function of WT and deltaF508 CFTR expressed within the same cell.

Molecular targeting of CFTR as a therapeutic approach to cystic fibrosis

One of the major challenges facing the pharmaceutical field is the identification of novel, 'druggable' targets common to distinct diseases that, despite their clinical diversity, share the same basic molecular defect(s) - thus, being termed 'horizontal diseases'. Membrane proteins constitute one of the largest families in the human genome and, given their major roles in cells and organisms, they are relevant to common human disorders such as cardiovascular disease and cancer, but also to rare genetic conditions such as cystic fibrosis (CF). Here, we review therapeutic approaches to correcting the basic defect in CF, which is caused mainly by the intracellular retention of a misfolded protein, and focus on various recent drug-discovery strategies for this important and paradigmatic disease. These strategies have possible applications in many membrane protein disorders, including other channelopathies. The mechanisms of action of potent and specific compounds, representing promising drug leads for CF pharmacotherapy, are explained and discussed.