Explore the vast range of titles available.

The ubiquitin-proteasome system degrades most intracellular proteins, including misfolded proteins. Proteasome functional insufficiency (PFI) has been observed in proteinopathies, such as desmin-related cardiomyopathy, and implicated in many common diseases, including dilated cardiomyopathy and ischemic heart disease. However, the pathogenic role of PFI has not been established. Here we created inducible Tg mice with cardiomyocyte-restricted overexpression of proteasome 28 subunit α (CR-PA28αOE) to investigate whether upregulation of the 11S proteasome enhances the proteolytic function of the proteasome in mice and, if so, whether the enhancement can rescue a bona fide proteinopathy and protect against ischemia/reperfusion (I/R) injury. We found that CR-PA28αOE did not alter the homeostasis of normal proteins and cardiac function, but did facilitate the degradation of a surrogate misfolded protein in the heart. By breeding mice with CR-PA28αOE with mice representing a well-established model of desmin-related cardiomyopathy, we demonstrated that CR-PA28αOE markedly reduced aberrant protein aggregation. Cardiac hypertrophy was decreased, and the lifespan of the animals was increased. Furthermore, PA28α knockdown promoted, whereas PA28α overexpression attenuated, accumulation of the mutant protein associated with desmin-related cardiomyopathy in cultured cardiomyocytes. Moreover, CR-PA28αOE limited infarct size and prevented postreperfusion cardiac dysfunction in mice with myocardial I/R injury. We therefore conclude that benign enhancement of cardiac proteasome proteolytic function can be achieved by CR-PA28αOE and that PFI plays a major pathogenic role in cardiac proteinopathy and myocardial I/R injury.

Myosin-binding protein C (MyBP-C) is an accessory protein of striated muscle thick filaments and a modulator of cardiac muscle contraction. Defects in the cardiac isoform, cMyBP-C, cause heart disease. cMyBP-C includes 11 Ig- and fibronectin-like domains and a cMyBP-C-specific motif. In vitro studies show that in addition to binding to the thick filament via its C-terminal region, cMyBP-C can also interact with actin via its N-terminal domains, modulating thin filament motility. Structural observations of F-actin decorated with N-terminal fragments of cMyBP-C suggest that cMyBP-C binds to actin close to the low Ca ²⁺ binding site of tropomyosin. This suggests that cMyBP-C might modulate thin filament activity by interfering with tropomyosin regulatory movements on actin. To determine directly whether cMyBP-C binding affects tropomyosin position, we have used electron microscopy and in vitro motility assays to study the structural and functional effects of N-terminal fragments binding to thin filaments. 3D reconstructions suggest that under low Ca ²⁺ conditions, cMyBP-C displaces tropomyosin toward its high Ca ²⁺ position, and that this movement corresponds to thin filament activation in the motility assay. At high Ca ²⁺, cMyBP-C had little effect on tropomyosin position and caused slowing of thin filament sliding. Unexpectedly, a shorter N-terminal fragment did not displace tropomyosin or activate the thin filament at low Ca ²⁺ but slowed thin filament sliding as much as the larger fragments. These results suggest that cMyBP-C may both modulate thin filament activity, by physically displacing tropomyosin from its low Ca ²⁺ position on actin, and govern contractile speed by an independent molecular mechanism.

Proteinopathy causes cardiac disease, remodeling, and heart failure but the pathological mechanisms remain obscure. Mutated αB-crystallin (CryAB ᴿ¹²⁰ᴳ), when expressed only in cardiomyocytes in transgenic (TG) mice, causes desmin-related cardiomyopathy, a protein conformational disorder. The disease is characterized by the accumulation of toxic misfolded protein species that present as perinuclear aggregates known as aggresomes. Previously, we have used the CryAB ᴿ¹²⁰ᴳ model to determine the underlying processes that result in these pathologic accumulations and to explore potential therapeutic windows that might be used to decrease proteotoxicity. We noted that total ventricular protein is hypoacetylated while hyperacetylation of α-tubulin, a substrate of histone deacetylase 6 (HDAC6) occurs. HDAC6 has critical roles in protein trafficking and autophagy, but its function in the heart is obscure. Here, we test the hypothesis that tubulin acetylation is an adaptive process in cardiomyocytes. By modulating HDAC6 levels and/or activity genetically and pharmacologically, we determined the effects of tubulin acetylation on aggregate formation in CryAB ᴿ¹²⁰ᴳ cardiomyocytes. Increasing HDAC6 accelerated aggregate formation, whereas siRNA-mediated knockdown or pharmacological inhibition ameliorated the process. HDAC inhibition in vivo induced tubulin hyperacetylation in CryAB ᴿ¹²⁰ᴳ TG hearts, which prevented aggregate formation and significantly improved cardiac function. HDAC6 inhibition also increased autophagic flux in cardiomyocytes, and increased autophagy in the diseased heart correlated with increased tubulin acetylation, suggesting that autophagy induction might underlie the observed cardioprotection. Taken together, our data suggest a mechanistic link between tubulin hyperacetylation and autophagy induction and points to HDAC6 as a viable therapeutic target in cardiovascular disease. Significance Proteotoxicity, or the accumulation of misfolded protein, can cause heart failure and effective therapeutics are needed to reduce protein accumulation in the myocardium. This study shows that inhibiting tubulin deacetylation by histone deacetylase 6 (HDAC6) is protective in a mouse model of proteinopathy-induced heart failure. Inhibiting tubulin deacetylation using the FDA-approved drug suberoylanilide hydroxamic acid (SAHA) reduced protein aggregates in cardiomyocytes and led to substantial improvement in cardiac function. Mechanistically, we show that inhibiting HDAC6 increases autophagy in cardiomyocytes, and that inducing autophagy with voluntary exercise also induces tubulin acetylation. This study shows that tubulin acetylation is important for autophagy stimulation in the heart and, importantly, sheds new light on the mechanism of autophagy induction with HDAC inhibitors.

During each heartbeat, cardiac contractility results from calcium-activated sliding of actin thin filaments toward the centers of myosin thick filaments to shorten cellular length. Cardiac myosin-binding protein C (cMyBP-C) is a component of the thick filament that appears to tune these mechanochemical interactions by its N-terminal domains transiently interacting with actin and/or the myosin S2 domain, sensitizing thin filaments to calcium and governing maximal sliding velocity. Both functional mechanisms are potentially further tunable by phosphorylation of an intrinsically disordered, extensible region of cMyBP-C’s N terminus, the M-domain. Using atomic force spectroscopy, electron microscopy, and mutant protein expression, we demonstrate that phosphorylation reduced the M-domain’s extensibility and shifted the conformation of the N-terminal domain from an extended structure to a compact configuration. In combination with motility assay data, these structural effects of M-domain phosphorylation suggest a mechanism for diminishing the functional potency of individual cMyBP-C molecules. Interestingly, we found that calcium levels necessary to maximally activate the thin filament mitigated the structural effects of phosphorylation by increasing M-domain extensibility and shifting the phosphorylated N-terminal fragments back to the extended state, as if unphosphorylated. Functionally, the addition of calcium to the motility assays ablated the impact of phosphorylation on maximal sliding velocities, fully restoring cMyBP-C’s inhibitory capacity. We conclude that M-domain phosphorylation may have its greatest effect on tuning cMyBP-C’s calcium-sensitization of thin filaments at the low calcium levels between contractions. Importantly, calcium levels at the peak of contraction would allow cMyBP-C to remain a potent contractile modulator, regardless of cMyBP-C’s phosphorylation state.

Circadian rhythmicity of cardiac ion-channel expression and of an index of myocardial repolarization is under the control of Klf15, a clock-dependent oscillator that is required for generating transient outward potassium current, and deficiencies or excesses of which cause loss of rhythmic variation in myocardial and abnormal repolarization, and an enhanced susceptibility to ventricular arrhythmias. How the biological clock influences the heart Several physiological parameters in the cardiovascular system show diurnal variation. Mukesh Jain and colleagues now provide a link between circadian rhythms and arrhythmogenesis in mice. They show that the transcription factor Klf15 is regulated by components of the circadian clock, and Klf15 in turn regulates expression of the ion channel KChIP2. In gain- and loss-of-function experiments, the authors show that Klf15 regulates temporal variation in cardiac repolarization and susceptibility to arrhythmias. The findings raise the possibility that circadian factors contribute to the diurnal variation seen in occurrence of sudden cardiac death. Sudden cardiac death exhibits diurnal variation in both acquired and hereditary forms of heart disease 1 , 2 , but the molecular basis of this variation is unknown. A common mechanism that underlies susceptibility to ventricular arrhythmias is abnormalities in the duration (for example, short or long QT syndromes and heart failure) 3 , 4 , 5 or pattern (for example, Brugada’s syndrome) 6 of myocardial repolarization. Here we provide molecular evidence that links circadian rhythms to vulnerability in ventricular arrhythmias in mice. Specifically, we show that cardiac ion-channel expression and QT-interval duration (an index of myocardial repolarization) exhibit endogenous circadian rhythmicity under the control of a clock-dependent oscillator, krüppel-like factor 15 ( Klf15 ). Klf15 transcriptionally controls rhythmic expression of Kv channel-interacting protein 2 (KChIP2), a critical subunit required for generating the transient outward potassium current 7 . Deficiency or excess of Klf15 causes loss of rhythmic QT variation, abnormal repolarization and enhanced susceptibility to ventricular arrhythmias. These findings identify circadian transcription of ion channels as a mechanism for cardiac arrhythmogenesis.

We assessed equity in the uptake of remote foot temperature monitoring (RTM) for amputation prevention throughout a large, integrated US healthcare system between 2019 and 2021, including comparisons across facilities and between patients enrolled and eligible patients not enrolled in RTM focusing on the Reach and Adoption dimensions of the Reach, Effectiveness, Adoption, Implementation, and Maintenance (RE-AIM) framework. To assess whether there was equitable use of RTM across facilities, we examined distributions of patient demographic, geographic, and facility characteristics across facility RTM use categories (e.g., no RTM use, and low, moderate, and high RTM use) among all eligible patients (n = 46,294). Second, to understand whether, among facilities using RTM, there was equitable enrollment of patients in RTM, we compared characteristics of patients enrolled in RTM (n = 1066) relative to a group of eligible patients not enrolled in RTM (n = 27,166) using logistic regression and including all covariates. RTM use increased substantially from an average of 11 patients per month to over 40 patients per month between 2019 and 2021. High-use RTM facilities had higher complexity and a lower ratio of patients per podiatrist but did not have consistent evidence of better footcare process measures. Among facilities offering RTM, enrollment varied by age, was inversely associated with Black race (vs. white), low income, living far from specialty care, and being in the highest quartiles of telehealth use prior to enrollment. Enrollment was positively associated with having osteomyelitis, Charcot foot, a partial foot amputation, BMI≥30 kg/m2, and high outpatient utilization. RTM growth was concentrated in a small number of higher-resourced facilities, with evidence of lower enrollment among those who were Black and lived farther from specialty care. Future studies are needed to identify and address barriers to uptake of new interventions like RTM to prevent exacerbating existing ulceration and amputation disparities.

Mitochondria play a critical role in mediating both apoptotic and necrotic cell death. The mitochondrial permeability transition (mPT) leads to mitochondrial swelling, outer membrane rupture and the release of apoptotic mediators. The mPT pore is thought to consist of the adenine nucleotide translocator, a voltage-dependent anion channel, and cyclophilin D (the Ppif gene product), a prolyl isomerase located within the mitochondrial matrix 1 , 2 . Here we generated mice lacking Ppif and mice overexpressing cyclophilin D in the heart. Ppif null mice are protected from ischaemia/reperfusion-induced cell death in vivo , whereas cyclophilin D-overexpressing mice show mitochondrial swelling and spontaneous cell death. Mitochondria isolated from the livers, hearts and brains of Ppif null mice are resistant to mitochondrial swelling and permeability transition in vitro . Moreover, primary hepatocytes and fibroblasts isolated from Ppif null mice are largely protected from Ca 2+ -overload and oxidative stress-induced cell death. However, Bcl-2 family member-induced cell death does not depend on cyclophilin D, and Ppif null fibroblasts are not protected from staurosporine or tumour-necrosis factor-α-induced death. Thus, cyclophilin D and the mitochondrial permeability transition are required for mediating Ca 2+ - and oxidative damage-induced cell death, but not Bcl-2 family member-regulated death.

A critical event in ischemia-based cell death is the opening of the mitochondrial permeability transition pore (MPTP). However, the molecular identity of the components of the MPTP remains unknown. Here, we determined that the Bcl-2 family members Bax and Bak, which are central regulators of apoptotic cell death, are also required for mitochondrial pore-dependent necrotic cell death by facilitating outer membrane permeability of the MPTP. Loss of Bax/Bak reduced outer mitochondrial membrane permeability and conductance without altering inner membrane MPTP function, resulting in resistance to mitochondrial calcium overload and necrotic cell death. Reconstitution with mutants of Bax that cannot oligomerize and form apoptotic pores, but still enhance outer membrane permeability, permitted MPTP-dependent mitochondrial swelling and restored necrotic cell death. Our data predict that the MPTP is an inner membrane regulated process, although in the absence of Bax/Bak the outer membrane resists swelling and prevents organelle rupture to prevent cell death. In all multicellular plants and animals, cells are continuously dying and being replaced. There are a number of different types of cell death, but two of the best studied are apoptosis and necrosis. Apoptosis, sometimes referred to as ‘cell suicide’, is a form of programmed cell death that is generally beneficial to the organism. Necrosis, however, occurs whenever cells are damaged—for example, due to a lack of oxygen—and can trigger harmful inflammation in surrounding tissue. Although the processes leading up to apoptosis and necrosis are very different, they both involve regulated changes in mitochondria—the organelles that supply cells with chemical energy. Mitochondria have a distinctive appearance, being enclosed by two membranes, the innermost of which is highly folded. During apoptosis, large pores form in the outer membranes of mitochondria. These pores are generated by two proteins—Bax and Bak—and they enable the mitochondrion to release proteins that activate processes involved in apoptosis. Pores also form in the mitochondrial membrane during necrosis. However, these mitochondrial permeability transition pores (MPTPs) occur simultaneously in both the inner and outer membranes and are thought to lead to swelling and rupture of mitochondria. Now, Karch et al. have shown that Bax and Bak are also involved in the formation of these permeability pores that underlie necrosis. When mouse cells that had been genetically modified to lack Bak and Bax were grown in cell culture, they were found to be resistant to substances that normally induce necrosis. Instead, their mitochondria continued to function normally, suggesting that MPTPs cannot form in the absence of Bak and Bax. Karch et al. then generated mice with heart cells that lack Bax and Bak, and deprived their hearts of oxygen to simulate a heart attack. Compared to normal mice, the genetically modified animals experienced less damage to their heart muscle, suggesting that the absence of Bax and Bak prevents cell death due to necrosis. If Bax and Bak are involved in both apoptosis and necrosis, inhibiting them could be a powerful therapeutic approach for preventing all forms of cell death during heart attacks or in certain degenerative diseases.

Background Parents’ perception and awareness about psychiatric illness in children and adolescents is an important determinant of early detection and treatment seeking for the condition. However, there has been limited information about the perception and awareness of parents about these issues as well as their preferred treatment options in Ethiopia. This study is, therefore, aimed at assessing the perception of parents about psychiatric illness in children and adolescents and their preferred treatment options in Jimma, Ethiopia. Method A cross-sectional study was conducted among 532 parents in Jimma City, Ethiopia from April to May 2013. Parents from the city were invited to participate in this study to assess their knowledge on causes, and manifestations of psychiatric illness in children and adolescents as well as their preferred treatment options if their children exhibited signs and symptoms of mental illness. Results Nearly three quarters of the parents identified genetic factors while approximately 20 % of them mentioned neuro-chemical disturbance as possible causes of their children’s mental health problems. On the other hand, magic, curse, and sin were mentioned as causes of mental health problems by 93.2, 81.8 and 73.9 % of the parents, respectively. Externalizing behavioral symptoms like “stealing from home, school or elsewhere” and internalizing symptoms like “being nervous in new situations and easily loses confidence” were perceived by 60.9 and 38.2 % of the parents, respectively. The majority (92.7 %) of parents agreed that they would seek treatment either from religious or spiritual healers if their children developed mental illness. Conclusions The low level of awareness about internalizing symptoms, the widespread traditional explanatory models as well as preference for traditional treatment options might present significant challenges to utilization of child and adolescent mental health services in this population. Public health intervention programs targeting parental attitude regarding the causes and treatment for child and adolescent mental health problems need to be designed and evaluated for their effectiveness in low-income settings. Additionally, including religious and spiritual leaders in the process of educating members of their respective churches and mosques should also be explored.