The mechanisms underlying the pathogenesis of chronic lung diseases, including chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis, remain incompletely understood. ...Mitochondria are vital cellular organelles crucial for energy generation, the maintenance of cellular metabolism, calcium homeostasis, intracellular signaling, and the regulation of cell death programs. Emerging evidence suggests that mitochondrial dysfunction plays a cardinal role in the initiation and progression of many human diseases, including chronic lung diseases. Upregulation of the autophagy program, a cellular adaptive mechanism for protein and organelle turnover, can occur in response to injury and may have a cell type-specific impact on the progression of disease. The selective autophagy subtype specific for mitochondria (mitophagy), regulated by PINK1 (phosphatase and tensin homolog-induced putative kinase 1), is a cellular response to accumulation of depolarized or injured mitochondria. Autophagy and mitophagy may be associated with either cellular protection or propagation of injury in a cell type-specific manner, and they may also be associated with modulation of cell death pathways. Genetic studies in mouse models have revealed opposing roles for PINK1 and/or mitophagy in the propagation of emphysema and fibrosis, whereas human studies have shown altered regulation of PINK1 in both idiopathic pulmonary fibrosis and COPD. We have also recently identified a role for mitophagy in regulating the cellular necroptosis program, with implications in COPD pathogenesis. Damage-associated molecular patterns released from injured mitochondria and/or necrotic cells may promote proinflammatory and profibrotic responses. In this review, we explore current experimental evidence for mitochondrial dysfunction as a key determinant in the pathogenesis of chronic lung diseases.
The Impact of Autophagy on Cell Death Modalities Ryter, Stefan W.; Mizumura, Kenji; Choi, Augustine M. K.
International Journal of Cell Biology,
2014, Volume:
2014, Issue:
2014
Journal Article
Peer reviewed
Open access
Autophagy represents a homeostatic cellular mechanism for the turnover of organelles and proteins, through a lysosome-dependent degradation pathway. During starvation, autophagy facilitates cell ...survival through the recycling of metabolic precursors. Additionally, autophagy can modulate other vital processes such as programmed cell death (e.g., apoptosis), inflammation, and adaptive immune mechanisms and thereby influence disease pathogenesis. Selective pathways can target distinct cargoes (e.g., mitochondria and proteins) for autophagic degradation. At present, the causal relationship between autophagy and various forms of regulated or nonregulated cell death remains unclear. Autophagy can occur in association with necrosis-like cell death triggered by caspase inhibition. Autophagy and apoptosis have been shown to be coincident or antagonistic, depending on experimental context, and share cross-talk between signal transduction elements. Autophagy may modulate the outcome of other regulated forms of cell death such as necroptosis. Recent advances suggest that autophagy can dampen inflammatory responses, including inflammasome-dependent caspase-1 activation and maturation of proinflammatory cytokines. Autophagy may also act as regulator of caspase-1 dependent cell death (pyroptosis). Strategies aimed at modulating autophagy may lead to therapeutic interventions for diseases in which apoptosis or other forms of regulated cell death may play a cardinal role.
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FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Heme oxygenase-1 (HO-1), a ubiquitous inducible stress-response protein, serves a major metabolic function in heme turnover. HO activity cleaves heme to form biliverdin-IXalpha, carbon monoxide (CO), ...and iron. Genetic experiments have revealed a central role for HO-1 in tissue homeostasis, protection against oxidative stress, and in the pathogenesis of disease. Four decades of research have witnessed not only progress in elucidating the molecular mechanisms underlying the regulation and function of this illustrious enzyme, but also have opened remarkable translational applications for HO-1 and its reaction products. CO, once regarded as a metabolic waste, can act as an endogenous mediator of cellular signaling and vascular function. Exogenous application of CO by inhalation or pharmacologic delivery can confer cytoprotection in preclinical models of lung/vascular injury and disease, based on anti-apoptotic, anti-inflammatory, and anti-proliferative properties. The bile pigments, biliverdin and bilirubin, end products of heme degradation, have also shown potential as therapeutics in vascular disease based on anti-inflammatory and anti-proliferative activities. Further translational and clinical trials research will unveil whether the HO-1 system or any of its reaction products can be successfully applied as molecular medicine in human disease.
Resolution of acute inflammation is an active event accompanied by biosynthesis of specialized proresolving mediators (SPM). We employed a systems approach to determine the impact of CO in resolution ...active programs during self-limited inflammation in mice. Compared with ambient air, inhaled CO gas (250 ppm) significantly limited PMN infiltration (∼44%, 6 h) into peritoneum and shortened resolution interval from 4 to 2 h. We profiled exudate lipid mediators (LM) via metabololipidomics, CO reduced leukotriene B4 (21 ± 11 versus 59 ± 24 pg/mouse, 6 h), and elevated SPM including resolvin (Rv) D1 (27 ± 4 versus 16 ± 5 pg/mouse) and maresin 1 (26 ± 9 versus 15 ± 3 pg/mouse). With human macrophages, SPM (10 pM-10 nM) elevated heme oxygenase (HO)-1 (∼50%, 8 h). CO also enhanced HO-1 expression and accumulation of RvD1 and RvD5, an action reversed by blockage of a key SPM biosynthesis enzyme 15-lipoxygenase type 1. Compared with normoxia, CO increased ∼30% phagocytosis of opsonized zymosan with human macrophage, which was further enhanced by SPM (∼100%). This CO increased phagocytosis was blocked by 15-lipoxygenase inhibition, and SPM stimulated phagocytosis was diminished by HO-1 inhibition. In murine peritonitis, both pre- and posttreatment with CO inhalation significantly increased macrophages carrying ingested apoptotic PMN in exudates and enhanced PMN apoptosis. Taken together, these results indicate that CO accelerates resolution of acute inflammation, shortens resolution intervals, enhances macrophage efferocytosis, and temporally regulates local levels of lipid mediator/SPM. Moreover, they provide proresolving mechanisms for HO-1/CO, which is part of the SPM-initiated resolution circuit.
Mitochondria in health, disease, and aging Harrington, John S; Ryter, Stefan W; Plataki, Maria ...
Physiological reviews,
10/2023, Volume:
103, Issue:
4
Journal Article
Peer reviewed
Mitochondria are well known as organelles responsible for the maintenance of cellular bioenergetics through the production of ATP. Although oxidative phosphorylation may be their most important ...function, mitochondria are also integral for the synthesis of metabolic precursors, calcium regulation, the production of reactive oxygen species, immune signaling, and apoptosis. Considering the breadth of their responsibilities, mitochondria are fundamental for cellular metabolism and homeostasis. Appreciating this significance, translational medicine has begun to investigate how mitochondrial dysfunction can represent a harbinger of disease. In this review, we provide a detailed overview of mitochondrial metabolism, cellular bioenergetics, mitochondrial dynamics, autophagy, mitochondrial damage-associated molecular patterns, mitochondria-mediated cell death pathways, and how mitochondrial dysfunction at any of these levels is associated with disease pathogenesis. Mitochondria-dependent pathways may thereby represent an attractive therapeutic target for ameliorating human disease.
The Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3) Task Force recently introduced a new clinical score termed quick Sequential (Sepsis-related) Organ Failure ...Assessment (qSOFA) for identification of patients at risk of sepsis outside the intensive care unit (ICU). We attempted to compare the discriminatory capacity of the qSOFA versus the Systemic Inflammatory Response Syndrome (SIRS) score for predicting mortality, ICU-free days, and organ dysfunction-free days in patients with suspicion of infection outside the ICU.
The Weill Cornell Medicine Registry and Biobank of Critically Ill Patients is an ongoing cohort of critically ill patients, for whom biological samples and clinical information (including vital signs before and during ICU hospitalization) are prospectively collected. Using such information, qSOFA and SIRS scores outside the ICU (specifically, within 8 hours before ICU admission) were calculated. This study population was therefore comprised of patients in the emergency department or the hospital wards who had suspected infection, were subsequently admitted to the medical ICU and were included in the Registry and Biobank.
One hundred fifty-two patients (67% from the emergency department) were included in this study. Sixty-seven percent had positive cultures and 19% died in the hospital. Discrimination of in-hospital mortality using qSOFA area under the receiver operating characteristic curve (AUC), 0.74; 95% confidence intervals (CI), 0.66-0.81 was significantly greater compared with SIRS criteria (AUC, 0.59; 95% CI, 0.51-0.67; p = 0.03). The qSOFA performed better than SIRS regarding discrimination for ICU-free days (p = 0.04), but not for ventilator-free days (p = 0.19), any organ dysfunction-free days (p = 0.13), or renal dysfunction-free days (p = 0.17).
In patients with suspected infection who eventually required admission to the ICU, qSOFA calculated before their ICU admission had greater accuracy than SIRS for predicting mortality and ICU-free days. However, it may be less clear whether qSOFA is also better than SIRS criteria for predicting ventilator free-days and organ dysfunction-free days. These findings may help clinicians gain further insight into the usefulness of qSOFA.
Chronic obstructive pulmonary disease (COPD) involves aberrant airway inflammatory responses to cigarette smoke (CS) that are associated with epithelial cell dysfunction, cilia shortening, and ...mucociliary clearance disruption. Exposure to CS reduced cilia length and induced autophagy in vivo and in differentiated mouse tracheal epithelial cells (MTECs). Autophagy-impaired (Becn1+/- or Map1lc3B-/-) mice and MTECs resisted CS-induced cilia shortening. Furthermore, CS increased the autophagic turnover of ciliary proteins, indicating that autophagy may regulate cilia homeostasis. We identified cytosolic deacetylase HDAC6 as a critical regulator of autophagy-mediated cilia shortening during CS exposure. Mice bearing an X chromosome deletion of Hdac6 (Hdac6-/Y) and MTECs from these mice had reduced autophagy and were protected from CS-induced cilia shortening. Autophagy-impaired Becn1-/-, Map1lc3B-/-, and Hdac6-/Y mice or mice injected with an HDAC6 inhibitor were protected from CS-induced mucociliary clearance (MCC) disruption. MCC was preserved in mice given the chemical chaperone 4-phenylbutyric acid, but was disrupted in mice lacking the transcription factor NRF2, suggesting that oxidative stress and altered proteostasis contribute to the disruption of MCC. Analysis of human COPD specimens revealed epigenetic deregulation of HDAC6 by hypomethylation and increased protein expression in the airways. We conclude that an autophagy-dependent pathway regulates cilia length during CS exposure and has potential as a therapeutic target for COPD.
Hyperoxia causes cell injury and death associated with reactive oxygen species formation and inflammatory responses. Recent studies show that hyperoxia-induced cell death involves apoptosis, ...necrosis, or mixed phenotypes depending on cell type, although the underlying mechanisms remain unclear. Using murine lung endothelial cells, we found that hyperoxia caused cell death by apoptosis involving both extrinsic (Fas-dependent) and intrinsic (mitochondria-dependent) pathways. Hyperoxia-dependent activation of the extrinsic apoptosis pathway and formation of the death-inducing signaling complex required NADPH oxidase-dependent reactive oxygen species production, because this process was attenuated by chemical inhibition, as well as by genetic deletion of the p47phox subunit, of the oxidase. Overexpression of heme oxygenase-1 prevented hyperoxia-induced cell death and cytochrome c release. Likewise, carbon monoxide, at low concentrations, markedly inhibited hyperoxia-induced endothelial cell death by inhibiting cytochrome c release and caspase-9/3 activation. Carbon monoxide, by attenuating hyperoxia-induced reactive oxygen species production, inhibited extrinsic apoptosis signaling initiated by death-inducing signal complex trafficking from the Golgi apparatus to the plasma membrane and downstream activation of caspase-8. We also found that carbon monoxide inhibited the hyperoxia-induced activation of Bcl-2-related proteins involved in both intrinsic and extrinsic apoptotic signaling. Carbon monoxide inhibited the activation of Bid and the expression and mitochondrial translocation of Bax, whereas promoted Bcl-XL/Bax interaction and increased Bad phosphorylation. We also show that carbon monoxide promoted an interaction of heme oxygenase-1 with Bax. These results define novel mechanisms underlying the antiapoptotic effects of carbon monoxide during hyperoxic stress.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Delay of tracheostomy for roughly 2 weeks after translaryngeal intubation of critically ill patients is the presently recommended practice and is supported by findings from large trials. However, ...these trials were suboptimally powered to detect small but clinically important effects on mortality. We aimed to assess the benefit of early versus late or no tracheostomy on mortality and pneumonia in critically ill patients who need mechanical ventilation.
We systematically searched PubMed, CINAHL, Embase, Web of Science, DOAJ, the Cochrane Library, references of relevant articles, scientific conference proceedings, and grey literature up to Aug 31, 2013, to identify randomised controlled trials comparing early tracheostomy (done within 1 week after translaryngeal intubation) with late (done any time after the first week of mechanical ventilation) or no tracheostomy and reporting on mortality or incidence of pneumonia in critically ill patients under mechanical ventilation. Our primary outcomes were all-cause mortality during the stay in the intensive-care unit and incidence of ventilator-associated pneumonia. Mortality during the stay in the intensive-care unit was a composite endpoint of definite intensive-care-unit mortality, presumed intensive-care-unit mortality, and 28-day mortality. We calculated pooled odds ratios (OR), pooled risk ratios (RR), and 95% CIs with a random-effects model. All but complications analyses were done on an intention-to-treat basis.
Analyses of 13 trials (2434 patients, 648 deaths) showed that all-cause mortality in the intensive-care unit was not significantly lower in patients assigned to the early versus the late or no tracheostomy group (OR 0·80, 95% CI 0·59-1·09; p=0·16). This result persisted when we considered only trials with a low risk of bias (511 deaths; OR 0·80, 95% CI 0·59-1·09; p=0·16; eight trials with 1934 patients). Incidence of ventilator-associated pneumonia was lower in mechanically ventilated patients assigned to the early versus the late or no tracheostomy group (691 cases; OR 0·60, 95% CI 0·41-0·90; p=0·01; 13 trials with 1599 patients). There was no evidence of a difference between the compared groups for 1-year mortality (788 deaths; RR 0·93, 95% CI 0·85-1·02; p=0·14; three trials with 1529 patients).
The synthesised evidence suggests that early tracheostomy is not associated with lower mortality in the intensive-care unit than late or no tracheostomy. However, early, compared with late or no, tracheostomy might be associated with a lower incidence of pneumonia; a finding that could question the present practice of delaying tracheostomy beyond the first week after translaryngeal intubation in mechanically ventilated patients. Nevertheless, the scarcity of a beneficial effect on long-term mortality and the potential complications associated with tracheostomy need careful consideration; thus, further studies focusing on long-term outcomes are warranted.
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