Members of the eukaryotic PIEZO family (the human orthologs are noted hPIEZO1 and hPIEZO2) form cation-selective mechanically-gated channels. We characterized the selectivity of human PIEZO1 ...(hPIEZO1) for alkali ions: K+, Na+, Cs+ and Li+; organic cations: TMA and TEA, and divalents: Ba2+, Ca2+, Mg2+ and Mn2+. All monovalent ions permeated the channel. At a membrane potential of -100 mV, Cs+, Na+ and K+ had chord conductances in the range of 35-55 pS with the exception of Li+, which had a significantly lower conductance of ~ 23 pS. The divalents decreased the single-channel permeability of K+, presumably because the divalents permeated slowly and occupied the open channel for a significant fraction of the time. In cell-attached mode, 90 mM extracellular divalents had a conductance for inward currents carried by the divalents of: 25 pS for Ba2+ and 15 pS for Ca2+ at -80 mV and 10 pS for Mg2+ at -50 mV. The organic cations, TMA and TEA, permeated slowly and attenuated K+ currents much like the divalents. As expected, the channel K+ conductance increased with K+ concentration saturating at ~ 45 pS and the KD of K+ for the channel was 32 mM. Pure divalent ion currents were of lower amplitude than those with alkali ions and the channel opening rate was lower in the presence of divalents than in the presence of monovalents. Exposing cells to the actin disrupting reagent cytochalasin D increased the frequency of openings in cell-attached patches probably by reducing mechanoprotection.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Autophagy-dependent mitochondrial turnover in response to cellular stress is necessary for maintaining cellular homeostasis. However, the mechanisms that govern the selective targeting of damaged ...mitochondria are poorly understood. Parkin, an E3 ubiquitin ligase, has been shown to be essential for the selective clearance of damaged mitochondria. Parkin is expressed in the heart, yet its function has not been investigated in the context of cardioprotection. We previously reported that autophagy is required for cardioprotection by ischemic preconditioning (IPC). In the present study, we used simulated ischemia (sI) in vitro and IPC of hearts to investigate the role of Parkin in mediating cardioprotection ex vivo and in vivo. In HL-1 cells, sI induced Parkin translocation to mitochondria and mitochondrial elimination. IPC induced Parkin translocation to mitochondria in Langendorff-perfused rat hearts and in vivo in mice subjected to regional IPC. Mitochondrial depolarization with an uncoupling agent similarly induced Parkin translocation to mitochondria in cells and Langendorff-perfused rat hearts. Mitochondrial loss was blunted in Atg5-deficient cells, revealing the requirement for autophagy in mitochondrial elimination. Consistent with previous reports indicating a role for p62/SQSTM1 in mitophagy, we found that depletion of p62 attenuated mitophagy and exacerbated cell death in HL-1 cardiomyocytes subjected to sI. While wild type mice showed p62 translocation to mitochondria and an increase in ubiquitination, Parkin knockout mice exhibited attenuated IPC-induced p62 translocation to the mitochondria. Importantly, ablation of Parkin in mice abolished the cardioprotective effects of IPC. These results reveal for the first time the crucial role of Parkin and mitophagy in cardioprotection.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Summary
Background
The interleukin‐17 cytokine family plays a central role in psoriasis pathogenesis.
Objectives
To evaluate the efficacy and safety of brodalumab, a human anti‐interleukin‐17 ...receptor antibody, in treating patients with moderate‐to‐severe plaque psoriasis.
Methods
In this phase III, double‐blind, placebo‐controlled study (NCT01708590; AMAGINE‐1), adult patients in the U.S.A., Canada and Europe were randomized to brodalumab (140 or 210 mg) or placebo every 2 weeks (Q2W), with an additional dose at week 1, for a 12‐week induction phase. At week 12, patients receiving brodalumab who achieved static Physician's Global Assessment 0 or 1 (sPGA success) were rerandomized to the placebo or induction dose. After week 16, patients with sPGA ≥ 3 were re‐treated with the induction dose. After ≥ 12 weeks of retreatment, patients with sPGA 2 for ≥ 4 weeks or sPGA ≥ 3 were rescued with brodalumab 210 mg Q2W. At week 12, patients randomized to brodalumab with sPGA ≥ 2 or placebo received brodalumab 210 mg Q2W. Coprimary end points were the percentage of patients with ≥ 75% improvement in Psoriasis Area and Severity Index score (PASI 75) and sPGA success at week 12.
Results
There were 661 patients randomized: 220 placebo, 219 brodalumab 140 mg and 222 brodalumab 210 mg. At week 12, 60% (140 mg) and 83% (210 mg) vs. 3% (placebo) achieved PASI 75, and 54% (140 mg) and 76% (210 mg) vs. 1% (placebo) achieved sPGA success. The safety profile was considered acceptable.
Conclusions
Brodalumab therapy resulted in significant clinical benefit and an acceptable safety profile in patients with moderate‐to‐severe plaque psoriasis.
What's already known about this topic?
Anti‐interleukin (anti‐IL)‐17 receptor A and anti‐IL‐17A antibodies have been shown to be efficacious in treating patients with moderate‐to‐severe plaque psoriasis.
What does this study add?
This study further demonstrates that brodalumab therapy in patients with moderate‐to‐severe plaque psoriasis results in a high degree of complete skin clearance.
This study also further elucidates the safety profile of brodalumab.
Linked Comment: Ormerod. Br J Dermatol 2016; 175:243–244
Plain language summary available online
Summary
Background
Tofacitinib is an oral Janus kinase inhibitor being investigated for psoriasis.
Objectives
To determine the 16‐week efficacy and safety of two oral tofacitinib doses vs. placebo in ...patients with moderate‐to‐severe chronic plaque psoriasis.
Methods
Patients in two similarly designed phase III studies (OPT Pivotal 1, NCT01276639, n = 901; OPT Pivotal 2, NCT01309737, n = 960) were initially randomized 2 : 2 : 1 to tofacitinib 10 or 5 mg or placebo, twice daily. Coprimary efficacy end points (week 16) included the proportion of patients achieving Physician's Global Assessment (PGA) of ‘clear’ or ‘almost clear’ (PGA response) and the proportion achieving ≥ 75% reduction in Psoriasis Area and Severity Index (PASI 75).
Results
Across OPT Pivotal 1 and OPT Pivotal 2, 745 patients received tofacitinib 5 mg, 741 received tofacitinib 10 mg and 373 received placebo. At week 16, a greater proportion of patients achieved PGA responses with tofacitinib 5 and 10 mg twice daily vs. placebo (OPT Pivotal 1, 41·9% and 59·2% vs. 9·0%; OPT Pivotal 2, 46·0% and 59·1% vs. 10·9%; all P < 0·001). Higher PASI 75 rates were observed with tofacitinib vs. placebo (OPT Pivotal 1, 39·9%, 59·2% and 6·2%, respectively, for tofacitinib 5 and 10 mg twice daily and placebo; OPT Pivotal 2, 46·0%, 59·6% and 11·4%; all P < 0·001 vs. placebo). Adverse event (AE) rates appeared generally similar across groups; rates of serious AEs, infections, malignancies and discontinuations due to AEs were low. Twelve patients reported herpes zoster across the tofacitinib treatment groups in both studies vs. none in the respective placebo groups. The most common AE across groups was nasopharyngitis.
Conclusions
Oral tofacitinib demonstrated significant efficacy vs. placebo during the initial 16 weeks of treatment in patients with moderate‐to‐severe psoriasis. Safety findings were consistent with prior studies.
What's already known about this topic?
The management of moderate‐to‐severe chronic plaque psoriasis has benefited from the introduction of biological therapies, but unmet needs still remain.
Tofacitinib is an oral Janus kinase inhibitor that is being investigated for psoriasis.
A phase IIb study demonstrated that oral tofacitinib is efficacious and well tolerated in the treatment of patients with plaque psoriasis over a 12‐week period.
What does this study add?
These phase III studies demonstrated that oral tofacitinib 5 and 10 mg twice daily is efficacious and well tolerated in the treatment of plaque psoriasis in a large, global patient population over a 16‐week period.
These studies provide support for tofacitinib as an innovative oral systemic option for the treatment of patients with psoriasis in the future.
Familial xerocytosis (HX) in humans is an autosomal disease that causes dehydration of red blood cells resulting in hemolytic anemia which has been traced to two individual mutations in the ...mechanosensitive ion channel, PIEZO1. Each mutation alters channel kinetics in ways that can explain the clinical presentation. Both mutations slowed inactivation and introduced a pronounced latency for activation. A conservative substitution of lysine for arginine (R2456K) eliminated inactivation and also slowed deactivation, indicating that this mutant’s loss of charge is not responsible for HX. Fitting the current vs. pressure data to Boltzmann distributions showed that the half-activation pressure, P ₁/₂, for M2225R was similar to that of WT, whereas mutations at position 2456 were left shifted. The absolute stress sensitivity was calibrated by cotransfection and comparison with MscL, a well-characterized mechanosensitive channel from bacteria that is driven by bilayer tension. The slope sensitivity of WT and mutant human PIEZO1 (hPIEZO1) was similar to that of MscL implying that the in-plane area increased markedly, by ∼6–20 nm ² during opening. In addition to the behavior of individual channels, groups of hPIEZO1 channels could undergo simultaneous changes in kinetics including a loss of inactivation and a long (∼200 ms), silent latency for activation. These observations suggest that hPIEZO1 exists in spatial domains whose global properties can modify channel gating. The mutations that create HX affect cation fluxes in two ways: slow inactivation increases the cation flux, and the latency decreases it. These data provide a direct link between pathology and mechanosensitive channel dysfunction in nonsensory cells.
Summary
Background
Tildrakizumab is a high‐affinity, humanized, IgG1/κ, anti‐interleukin (IL)‐23p19 monoclonal antibody that does not bind human IL‐12 or p40 is being developed for the treatment of ...chronic plaque psoriasis.
Objectives
To evaluate the safety and efficacy of subcutaneous tildrakizumab in patients with moderate‐to‐severe chronic plaque psoriasis.
Methods
A three‐part, randomized, double‐blind, phase IIb trial was conducted in 355 adults with chronic plaque psoriasis. Participants were randomized to receive subcutaneous tildrakizumab (5, 25, 100, 200 mg) or placebo at weeks 0 and 4 (part I) and every 12 weeks thereafter until week 52 (part II). Study drug was discontinued at week 52 and participants were followed through week 72 (part III). Primary efficacy end point was Psoriasis Area and Severity Index (PASI) 75 response at week 16. Adverse events (AEs) and vital signs were monitored throughout the study.
Results
At week 16, PASI 75 responses were 33·3% (n = 14), 64·4% (n = 58), 66·3% (n = 59), 74·4% (n = 64) and 4·4% (n = 2) in the 5‐, 25‐, 100‐ and 200‐mg tildrakizumab and placebo groups, respectively (P ≤ 0·001 for each tildrakizumab dose vs. placebo). PASI 75 response was generally maintained through week 52; only eight of 222 participants who achieved PASI 75 response at week 52 and continued to part III relapsed following discontinuation up to week 72. Possible drug‐related serious AEs included bacterial arthritis and lymphoedema (part I), and melanoma, stroke, epiglottitis and knee infection (part II).
Conclusions
Tildrakizumab had treatment effects that were superior to placebo, maintained for 52 weeks of treatment, and persisted for 20 weeks after cessation. Tildrakizumab was generally safe and well tolerated. These results suggest that IL‐23p19 is a key target for suppressing psoriasis.
What's already known about this topic?
Immune mechanism‐specific targeted biological treatments have successfully demonstrated improvements in clinical outcomes in patients with chronic plaque psoriasis.
Selective interleukin (IL)‐23 inhibition has been a recent target for novel therapies and small initial phase I trials have confirmed safety and preliminary efficacy in humans.
What does this study add?
This is the first large‐scale phase II trial to evaluate a monoclonal antibody that selectively inhibits IL‐23 in patients with chronic plaque psoriasis
.
Linked Comment: Strober, Br J Dermatol 2015; 173: 887–888.
Objective
Browning of white adipose tissue (WAT) promotes increased energy expenditure through the action of uncoupling protein 1 (UCP1) and is an attractive target to promote weight loss in obesity. ...Lowering of mitochondrial membrane potential by UCP1 is uniquely beneficial in this context; in other tissues, reduced membrane potential promotes mitochondrial clearance via mitophagy. It is unknown how parkin‐mediated mitophagy is regulated in beige adipocytes.
Methods
The relationship between parkin expression and WAT browning was investigated in 3T3‐L1 adipocytes and parkin‐deficient male C57BL/6 mice in response to pharmacological browning stimuli.
Results
Rosiglitazone treatment in 3T3‐L1 adipocytes promoted mitochondrial biogenesis, UCP1 expression, and mitochondrial uncoupling. Parkin expression was decreased and reduced mitochondrial‐associated parkin, and p62 indicated a reduction in mitophagy activity. Parkin overexpression prevented mitochondrial remodeling in response to rosiglitazone. In CL 316,243‐treated wild‐type mice, decreased parkin expression was observed in subcutaneous inguinal WAT, where UCP1 was strongly induced. CL 316,243 treatment weakly induced UCP1 expression in the gonadal depot, where parkin expression was unchanged. In contrast, parkin‐deficient mice exhibited robust UCP1 expression in gonadal WAT following CL 316,243 treatment.
Conclusions
WAT browning was associated with a decrease in parkin‐mediated mitophagy, and parkin expression antagonized browning of WAT.
Mechanosensitive ion channels are force-transducing enzymes that couple mechanical stimuli to ion flux. Understanding the gating mechanism of mechanosensitive channels is challenging because the ...stimulus seen by the channel reflects forces shared between the membrane, cytoskeleton and extracellular matrix. Here we examine whether the mechanosensitive channel PIEZO1 is activated by force-transmission through the bilayer. To achieve this, we generate HEK293 cell membrane blebs largely free of cytoskeleton. Using the bacterial channel MscL, we calibrate the bilayer tension demonstrating that activation of MscL in blebs is identical to that in reconstituted bilayers. Utilizing a novel PIEZO1-GFP fusion, we then show PIEZO1 is activated by bilayer tension in bleb membranes, gating at lower pressures indicative of removal of the cortical cytoskeleton and the mechanoprotection it provides. Thus, PIEZO1 channels must sense force directly transmitted through the bilayer.
Human PIEZO1: Removing Inactivation Bae, Chilman; Gottlieb, Philip A.; Sachs, Frederick
Biophysical journal,
08/2013, Letnik:
105, Številka:
4
Journal Article
Recenzirano
Odprti dostop
PIEZO1 is an inactivating eukaryotic cation-selective mechanosensitive ion channel. Two sites have been located in the channel that when individually mutated lead to xerocytotic anemia by slowing ...inactivation. By introducing mutations at two sites, one associated with xerocytosis and the other artificial, we were able to remove inactivation. The double mutant (DhPIEZO1) has a substitution of arginine for methionine (M2225R) and lysine for arginine (R2456K). The loss of inactivation was accompanied by ∼30-mmHg shift of the activation curve to lower pressures and slower rates of deactivation. The slope sensitivity of gating was the same for wild-type and mutants, indicating that the dimensional changes between the closed and open state are unaffected by the mutations. The unitary channel conductance was unchanged by mutations, so these sites are not associated with pore. DhPIEZO1 was reversibly inhibited by the peptide GsMTx4 that acted as a gating modifier. The channel kinetics were solved using complex stimulus waveforms and the data fit to a three-state loop in detailed balance. The reaction had two pressure-dependent rates, closed to open and inactivated to closed. Pressure sensitivity of the opening rate with no sensitivity of the closing rate means that the energy barrier between them is located near the open state. Mutant cycle analysis of inactivation showed that the two sites interacted strongly, even though they are postulated to be on opposite sides of the membrane.
To develop comprehensive recommendations for the treatment of the various clinical manifestations of psoriatic arthritis (PsA) based on evidence obtained from a systematic review of the literature ...and from consensus opinion.
Formal literature reviews of treatment for the most significant discrete clinical manifestations of PsA (skin and nails, peripheral arthritis, axial disease, dactylitis and enthesitis) were performed and published by members of the Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA). Treatment recommendations were drafted for each of the clinical manifestations by rheumatologists, dermatologists and PsA patients based on the literature reviews and consensus opinion. The level of agreement for the individual treatment recommendations among GRAPPA members was assessed with an online questionnaire.
Treatment recommendations were developed for peripheral arthritis, axial disease, psoriasis, nail disease, dactylitis and enthesitis in the setting of PsA. In rotal, 19 recommendations were drafted, and over 80% agreement was obtained on 16 of them. In addition, a grid that factors disease severity into each of the different disease manifestations was developed to help the clinician with treatment decisions for the individual patient from an evidenced-based perspective.
Treatment recommendations for the cardinal physical manifestations of PsA were developed based on a literature review and consensus between rheumatologists and dermatologists. In addition, a grid was established to assist in therapeutic reasoning and decision making for individual patients. It is anticipated that periodic updates will take place using this framework as new data become available.
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