Aldosterone signaling through transient receptor potential melastatin 7 cation channel (TRPM7) and its α-kinase domain

We demonstrated a role for the Mg2 + transporter TRPM7, a bifunctional protein with channel and α-kinase domains, in aldosterone signaling. Molecular mechanisms underlying this are elusive. Here we investigated the function of TRPM7 and its α-kinase domain on Mg2 + and pro-inflammatory signaling by aldosterone. Kidney cells (HEK-293) expressing wild-type human TRPM7 (WThTRPM7) or constructs in which the α-kinase domain was deleted (ΔKinase) or rendered inactive with a point mutation in the ATP binding site of the α-kinase domain (K1648R) were studied. Aldosterone rapidly increased [Mg2 +]i and stimulated NADPH oxidase-derived generation of reactive oxygen species (ROS) in WT hTRPM7 and TRPM7 kinase dead mutant cells. Translocation of annexin-1 and calpain-II and spectrin cleavage (calpain target) were increased by aldosterone in WT hTRPM7 cells but not in α-kinase-deficient cells. Aldosterone stimulated phosphorylation of MAP kinases and increased expression of pro-inflammatory mediators ICAM-1, Cox-2 and PAI-1 in Δkinase and K1648R cells, effects that were inhibited by eplerenone (mineralocorticoid receptor (MR) blocker). 2-APB, a TRPM7 channel inhibitor, abrogated aldosterone-induced Mg2 + responses in WT hTRPM7 and mutant cells. In 2-APB-treated ΔKinase and K1648R cells, aldosterone-stimulated inflammatory responses were unchanged. These data indicate that aldosterone stimulates Mg2 + influx and ROS production in a TRPM7-sensitive, kinase-insensitive manner, whereas activation of annexin-1 requires the TRPM7 kinase domain. Moreover TRPM7 α-kinase modulates inflammatory signaling by aldosterone in a TRPM7 channel/Mg2 +-independent manner. Our findings identify novel mechanisms for non-genomic actions of aldosterone involving differential signaling through MR-activated TRPM7 channel and α-kinase

Turing Instability in a Boundary-fed System

The formation of localized structures in the chlorine dioxide-idodine-malonic acid (CDIMA) reaction-diffusion system is investigated numerically using a realistic model of this system. We analyze the one-dimensional patterns formed along the gradients imposed by boundary feeds, and study their linear stability to symmetry-breaking perturbations (Turing instability) in the plane transverse to these gradients. We establish that an often-invoked simple local linear analysis which neglects longitudinal diffusion is inappropriate for predicting the linear stability of these patterns. Using a fully nonuniform analysis, we investigate the structure of the patterns formed along the gradients and their stability to transverse Turing pattern formation as a function of the values of two control parameters: the malonic acid feed concentration and the size of the reactor in the dimension along the gradients. The results from this investigation are compared with existing experiments.Comment: 41 pages, 18 figures, to be published in Physical Review

Amplitude equations near pattern forming instabilities for strongly driven ferromagnets

A transversally driven isotropic ferromagnet being under the influence of a static external and an uniaxial internal anisotropy field is studied. We consider the dissipative Landau-Lifshitz equation as the fundamental equation of motion and treat it in $1+1$~dimensions. The stability of the spatially homogeneous magnetizations against inhomogeneous perturbations is analyzed. Subsequently the dynamics above threshold is described via amplitude equations and the dependence of their coefficients on the physical parameters of the system is determined explicitly. We find soft- and hard-mode instabilities, transitions between sub- and supercritical behaviour, various bifurcations of higher codimension, and present a series of explicit bifurcation diagrams. The analysis of the codimension-2 point where the soft- and hard-mode instabilities coincide leads to a system of two coupled Ginzburg-Landau equations.Comment: LATeX, 25 pages, submitted to Z.Phys.B figures available via [email protected] in /pub/publications/frank/zpb_95 (postscript, plain or gziped

Transition in incompressible boundary layers with two-dimensional excrescences

An experimental investigation of the transition process in boundary layers subjected to forward- or aft-facing two-dimensional step excrescences is described. The objective of the work was to characterize the variation of transition Reynolds numbers with measurable roughness and boundary layer parameters, with the specific goal of specifying new tolerance criteria for laminar flow airfoils, alongside a fundamental investigation of linear boundary layer stability mechanisms. Results from an ongoing program of increasing complexity on effects of pressure gradient on excrescence-induced transition are presented. Preliminary N-factor calculations are used to determine the effects of boundary layer stability and attempt to isolate the effect of the disturbance due to the excrescence

Transitions/relaxations in polyester adhesive/PET system

The correlations between the transitions and the dielectric relaxation processes of the oriented poly(ethylene terephthalate) (PET) pre-impregnated of the polyester thermoplastic adhesive have been investigated by differential scanning calorimetry (DSC) and dynamic dielectric spectroscopy (DDS). The thermoplastic polyester adhesive and the oriented PET films have been studied as reference samples. This study evidences that the adhesive chain segments is responsible for the physical structure evolution in the PET-oriented film. The transitions and dielectric relaxation modes’ evolutions in the glass transition region appear characteristic of the interphase between adhesive and PET film, which is discussed in terms of molecular mobility. The storage at room temperature of the adhesive tape involves the heterogeneity of the physical structure, characterized by glass transition dissociation. Thus, the correlation between the transitions and the dielectric relaxation processes evidences a segregation of the amorphous phases. Therefore, the physical structure and the properties of the material have been linked to the chemical characteristics

Phase Dynamics of Nearly Stationary Patterns in Activator-Inhibitor Systems

The slow dynamics of nearly stationary patterns in a FitzHugh-Nagumo model are studied using a phase dynamics approach. A Cross-Newell phase equation describing slow and weak modulations of periodic stationary solutions is derived. The derivation applies to the bistable, excitable, and the Turing unstable regimes. In the bistable case stability thresholds are obtained for the Eckhaus and the zigzag instabilities and for the transition to traveling waves. Neutral stability curves demonstrate the destabilization of stationary planar patterns at low wavenumbers to zigzag and traveling modes. Numerical solutions of the model system support the theoretical findings

The Effect of Acoustic Forcing on Instabilities and Breakdown in Swept-Wing Flow over a Backward-Facing Step

Instability interaction and breakdown were experimentally investigated in the flow over a swept backward-facing step. Acoustic forcing was used to excite the Tollmien-Schlichting (TS) instability and to acquire phase-locked results. The phase-averaged results illustrate the complex nature of the interaction between the TS and stationary cross flow instabilities. The weak stationary cross flow disturbance causes a distortion of the TS wavefront. The breakdown process is characterized by large positive and negative spikes in velocity. The positive spikes occur near the same time and location as the positive part of the TS wave. Higher-order spectral analysis was used to further investigate the nonlinear interactions between the TS instability and the traveling cross flow disturbances. The results reveal that a likely cause for the generation of the spikes corresponds to nonlinear interactions between the TS, traveling cross flow, and stationary cross flow disturbances. The spikes begin at low amplitudes of the unsteady and steady disturbances (2-4% U (sub e) (i.e. boundary layer edge velocity)) but can achieve very large amplitudes (20-30 percent U (sub e) (i.e. boundary layer edge velocity)) that initiate an early, though highly intermittent, breakdown to turbulence

Multiple molecular mechanisms form a positive feedback loop driving amyloid β42 peptide-induced neurotoxicity via activation of the TRPM2 channel in hippocampal neurons

Emerging evidence supports an important role for the ROS-sensitive TRPM2 channel in mediating age-related cognitive impairment in Alzheimer’s disease (AD), particularly neurotoxicity resulting from generation of excessive neurotoxic Aβ peptides. Here we examined the elusive mechanisms by which Aβ₄₂ activates the TRPM2 channel to induce neurotoxicity in mouse hippocampal neurons. Aβ₄₂-induced neurotoxicity was ablated by genetic knockout (TRPM2-KO) and attenuated by inhibition of the TRPM2 channel activity or activation through PARP-1. Aβ₄₂-induced neurotoxicity was also inhibited by treatment with TPEN used as a Zn²⁺-specific chelator. Cell imaging revealed that Aβ₄₂-induced lysosomal dysfunction, cytosolic Zn²⁺ increase, mitochondrial Zn²⁺ accumulation, loss of mitochondrial function, and mitochondrial generation of ROS. These effects were suppressed by TRPM2-KO, inhibition of TRPM2 or PARP-1, or treatment with TPEN. Bafilomycin-induced lysosomal dysfunction also resulted in TRPM2-dependent cytosolic Zn²⁺ increase, mitochondrial Zn²⁺ accumulation, and mitochondrial generation of ROS, supporting that lysosomal dysfunction and accompanying Zn²⁺ release trigger mitochondrial Zn²⁺ accumulation and generation of ROS. Aβ₄₂-induced effects on lysosomal and mitochondrial functions besides neurotoxicity were also suppressed by inhibition of PKC and NOX. Furthermore, Aβ₄₂-induced neurotoxicity was prevented by inhibition of MEK/ERK. Therefore, our study reveals multiple molecular mechanisms, including PKC/NOX-mediated generation of ROS, activation of MEK/ERK and PARP-1, lysosomal dysfunction and Zn²⁺ release, mitochondrial Zn²⁺ accumulation, loss of mitochondrial function, and mitochondrial generation of ROS, are critically engaged in forming a positive feedback loop that drives Aβ₄₂-induced activation of the TRPM2 channel and neurotoxicity in hippocampal neurons. These findings shed novel and mechanistic insights into AD pathogenesis

Signalling mechanisms mediating Zn2+-induced TRPM2 channel activation and death cell in microglial cells

Excessive Zn2+ causes brain damage via promoting ROS generation. Here we investigated the role of ROS-sensitive TRPM2 channel in H2O2/Zn2+-induced Ca2+ signalling and cell death in microglial cells. H2O2/Zn2+ induced concentration-dependent increases in cytosolic Ca2+ concentration ([Ca2+]c), which was inhibited by PJ34, a PARP inhibitor, and abolished by TRPM2 knockout (TRPM2-KO). Pathological concentrations of H2O2/Zn2+ induced substantial cell death that was inhibited by PJ34 and DPQ, PARP inhibitors, 2-APB, a TRPM2 channel inhibitor, and prevented by TRPM2-KO. Further analysis indicate that Zn2+ induced ROS production, PARP-1 stimulation, increase in the [Ca2+]c and cell death, which were suppressed by chelerythrine, a protein kinase C inhibitor, DPI, a NADPH-dependent oxidase (NOX) inhibitor, GKT137831, a NOX1/4 inhibitor, and Phox-I2, a NOX2 inhibitor. Furthermore, Zn2+-induced PARP-1 stimulation, increase in the [Ca2+]c and cell death were inhibited by PF431396, a Ca2+-sensitive PYK2 inhibitor, and U0126, a MEK/ERK inhibitor. Taken together, our study shows PKC/NOX-mediated ROS generation and PARP-1 activation as an important mechanism in Zn2+-induced TRPM2 channel activation and, TRPM2-mediated increase in the [Ca2+]c to trigger the PYK2/MEK/ERK signalling pathway as a positive feedback mechanism that amplifies the TRPM2 channel activation. Activation of these TRPM2-depenent signalling mechanisms ultimately drives Zn2+-induced Ca2+ overloading and cell death

Effect of Personalized Incentives on Dietary Quality of Groceries Purchased A Randomized Crossover Trial

Importance Many factors are associated with food choice. Personalized interventions could help improve dietary intake by using individual purchasing preferences to promote healthier grocery purchases. Objective To test whether a healthy food incentive intervention using an algorithm incorporating customer preferences, purchase history, and baseline diet quality improves grocery purchase dietary quality and spending on healthy foods. Design, Setting, and Participants This was a 9-month randomized clinical crossover trial (AB–BA) with a 2- to 4-week washout period between 3-month intervention periods. Participants included 224 loyalty program members at an independent Rhode Island supermarket who completed baseline questionnaires and were randomized from July to September 2018 to group 1 (AB) or group 2 (BA). Data analysis was performed from September 2019 to May 2020. Intervention Participants received personalized weekly coupons with nutrition education during the intervention period (A) and occasional generic coupons with nutrition education during the control period (B). An automated study algorithm used customer data to allocate personalized healthy food incentives to participant loyalty cards. All participants received a 5% grocery discount. Main Outcomes and Measures Grocery Purchase Quality Index–2016 (GPQI-16) scores (range, 0-75, with higher scores denoting healthier purchases) and percentage spending on targeted foods were calculated from cumulative purchasing data. Participants in the top and bottom 1% of spending were excluded. Paired t tests examined between-group differences. Results The analytical sample included 209 participants (104 in group 1 and 105 in group 2), with a mean (SD) age of 55.4 (14.0) years. They were predominantly non-Hispanic White (193 of 206 participants [94.1%]) and female (187 of 207 participants [90.3%]). Of 161 participants with income data, 81 (50.3%) had annual household incomes greater than or equal to $100 000. Paired t tests showed that the intervention increased GPQI-16 scores (between-group difference, 1.06; 95% CI, 0.27-1.86; P = .01) and percentage spending on targeted foods (between-group difference, 1.38%; 95% CI, 0.08%-2.69%; P = .04). During the initial intervention period, group 1 (AB) and group 2 (BA) had similar mean (SD) GPQI-16 scores (41.2 [6.6] vs 41.0 [7.5]) and mean (SD) percentage spending on targeted healthy foods (32.0% [10.8%] vs 31.0% [10.5%]). During the crossover intervention period, group 2 had a higher mean (SD) GPQI-16 score than group 1 (42.9 [7.7] vs 41.0 [6.8]) and mean (SD) percentage spending on targeted foods (34.0% [12.1%] vs 32.0% [13.1%]). Conclusions and Relevance This pilot trial demonstrated preliminary evidence for the effectiveness of a novel personalized healthy food incentive algorithm to improve grocery purchase dietary quality. Trial Registration ClinicalTrials.gov Identifier: NCT0374805