Title efficacy of phosphodiesterase 5 inhibitor on distant burn-induced muscle autophagy, microcirculation, and survival rate

Mito-kaede photoactivation and chase experiment for mitophagy: optimizing flux measurement via fluid exchange system

Modulating autophagy and mitophagy, vital cellular quality control systems, offer therapeutic potential for critical illnesses. However, limited drug screening options hinder progress. We present a novel assay using the photoswitchable fluorescent reporter, mito-Kaede, to quantify mitophagy flux. Mito-Kaede's superior UV-induced photoconversion and brightness post-conversion make it ideal for prolonged mitochondrial dynamics tracking. Its specificity in responding to mitophagy, confirmed by parkin-knockout cells, adds value. When coupled with a custom fluid exchange system, enabling efficient medium changes, precise mitophagy observations become feasible. This mitophagy assay, alongside our methodological insights, can decipher mitophagy's role in pathology and supports drug screening efforts.

Vardenafil alleviates cigarette smoke-induced chronic obstructive pulmonary disease by activating autophagy via the AMPK/mTOR signalling pathway: an in vitro and in vivo study

Chronic obstructive pulmonary disease (COPD) has always attracted global attention with its high prevalence, incidence rate, and mortality. Exposure to cigarette smoke is one of main causes of COPD. Therefore, it is still necessary to study its pathogenesis and find new therapeutic strategies for early COPD prevention and treatment. Vardenafil, a type 5 phosphodiesterase (PDE5) inhibitor, is known to have an efficient therapy in some cardiovascular, pulmonary, and vascular diseases, which is an important mechanism for COPD. However, it still loss relevant research on whether vardenafil is effective in COPD and its mechanism. In this study, the cigarette smoke inhalation was performed to establish cigarette smoke-induced COPD model using C57BL/6 mice and 16HBE cells were treated with cigarette smoke extract (CSE). Mice were treated with vardenafil for 30 d. Then condition of lung injury was evaluated using histological analysis. The content of cytokines and the number of inflammatory cells in lung tissues or bronchoalveolar lavage fluid were measured. Additionally, western blot analysis was employed to evaluate the activation of adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK)/mechanistic target of rapamycin (mTOR)-mediated autophagy in vitro. The results showed that vardenafil abolished CSE's effect by activating autophagy via the AMPK/mTOR signalling pathway in vitro. Vardenafil attenuated cigarette smoke-induced lung injury and inflammation response by activating autophagy via the AMPK/mTOR signalling pathway in vivo. These results provide valuable insights into the molecular mechanisms underlying vardenafil's beneficial effects in cigarette smoke-induced COPD treatment. In conclusion, vardenafil alleviates cigarette smoke-induced experimental COPD by activating autophagy via the AMPK/mTOR signalling pathway.

Advanced oxidation protein products mediate human keratinocytes apoptosis by inducing cell autophagy through the mTOR-Beclin-1 pathway

Excessive keratinocyte apoptosis leads to impaired wound healing. Recently, advanced oxidation protein products (AOPP) have been recognized as a marker of oxidative stress and a potent inducer of apoptosis. Previously, we have demonstrated that extracellular AOPP accumulation induced keratinocyte apoptosis, and we discovered that autophagy was involved. To further elucidate the role and mechanism of autophagy in AOPP-induced-apoptosis of keratinocytes, we treated HaCaT cells with increasing concentrations of AOPP-human serum albumin or with AOPP-human serum albumin for increasing durations. Cyto-ID solution staining was used to assess cell autophagy using confocal laser scanning microscopy. Autophagy-related protein interactions were investigated using western blot analysis. Exposure of HaCaT cells to AOPP decreased the expression of mammalian target of rapamycin (mTOR) and increased the expression of autophagy-related proteins Beclin-l and LC3, and eventually led to autophagy. Furthermore, an autophagy agonist significantly decreased the expression of apoptosis-related proteins. Taken together, we showed that accumulation of extracellular AOPP induced autophagy in HaCaT cells via a reactive oxygen species-dependent, mTOR-Beclin-1-mediated pathway, and that excessive autophagy-mediated apoptosis, which resulted in delayed wound healing.

The Effect of Udenafil on Stasis Zone in an Experimental Burn Model

BACKGROUND

Management of the burn injuries is still a problematic issue because the stasis zone may become necrotic. We hypothesized that udenafil, a potent phospodiesterase inhibitor, can be beneficial in burn treatment by enhancing the viability of the stasis zone.

METHODS

Fifteen Wistar rats were randomly divided into 3 groups. Comb burn injury model was conducted bilaterally on the back of rats in each subject. Group 1 received 1 mL/d of saline orally for 7 days. Group 2 received 10 mg/kg per day of udenafil for 7 days. Group 3 received 20 mg/kg per day of udenafil for 7 days. At the end of seventh day, gross morphological and histopathological samples of stasis zone survival were evaluated.

RESULTS

Histopathological examination of groups 2 and 3 revealed that the stasis zone was mostly viable. The mean necrotic area and severity of inflammation was significantly higher in the control group compared with the treatment groups. Significant differences were determined in treatment groups compared with control group in terms of vital stasis zone area and histopathological parameters.

CONCLUSIONS

Udenafil treatment improved tissue survival on zone of stasis in. Future experimental studies should be conducted to develop zone of stasis treatment protocols combining udenafil with potent anti-inflammatory and antioxidant drugs.

A clinical comparison of an endothelin receptor antagonist and phosphodiesterase type 5 inhibitors for treating digital ulcers of systemic sclerosis

OBJECTIVES

To assess the efficacy of an endothelin receptor antagonist (ERA) and phosphodiesterase type5 inhibitors (PDE5is) for treating SSc-related digital ulcers (DUs).

METHODS

This prospective, multicentre, observational cohort study recruited patients with active SSc-related DUs from 13 medical centres in South Korea. The primary outcome was time to cardinal ulcer (CU) healing. A secondary outcome was time to new DU occurrence. Patients were followed up 4, 8, 12 and 24 weeks after treatment initiation.

RESULTS

Sixty-three patients were analysed. Their mean age was 49.9 years (s.d. 11.4) and 49 were female. Twenty-eight had limited SSc. Forty-nine patients received ERA, 11 received a PDE5i (9 sildenafil, 1 udenafil and 1 tadalafil) and 3 received other medication. The hazard ratio (HR) for time to CU healing in the ERA group vs the PDE5i group was 0.75 (95% CI 0.35, 1.64; P = 0.47) in an unadjusted model and 0.80 (95% CI 0.36, 1.78; P = 0.59) in a model adjusted for age, sex, use of calcium channel blockers (CCBs), total DU number and initial CU area. The HR for new DU development in the ERA group vs the PDE5i group was 0.39 (95% CI 0.16, 0.93; P = 0.03) in an unadjusted model and 0.32 (95% CI 0.13, 0.81; P = 0.02) in an adjusted model. No patients receiving CCBs developed new DUs at 24 weeks.

CONCLUSION

Time to CU healing is comparable for ERA and PDE5i. ERAs are more effective in reducing new DU occurrence than PDE5is. CCBs may be effective as a background medication.

Burn-Induced Microglia Activation is Associated With Motor Neuron Degeneration and Muscle Wasting in Mice

INTRODUCTION

Burn injury (BI) leads to both systemic and neuro-inflammation and is associated with muscle wasting and weakness, which increase morbidity and mortality. Disuse atrophy is concomitantly present in BI patients. Most studies have focused on muscle with little attention to role of central nervous system (CNS) in the neuromuscular changes. We tested the hypothesis that BI-induced muscle wasting stems from CNS microglia activation and cytokines and chemokine release, which is associated with spinal ventral horn motor neuron degeneration.

METHODS

Body surface (35%) BI, immobilization alone (Immob), BI with immobilization (BI + Immob), or Sham BI were administered to mice. Spinal cord (L3-L4 segments) and skeletal muscle tissues were harvested on days 7 and 14 after perturbations to examine microglia, motor neuron, and skeletal muscle changes.

RESULTS

BI and BI + Immob significantly (P < 0.05) activated microglia, evidenced by its increased density around motor neurons, upregulated neuroinflammation-marker, translocator protein 18 kDa expression and inflammatory cytokines (interleukin-1β, tumor necrosis factor-α) and/or chemokines (CXCL2) expression at days 7 and 14. Ventral horn motor neurons apoptosis and downregulation were observed at both periods after BI and was significantly magnified by concomitant BI + Immob. BI and more prominently BI + Immob disintegrated and fragmented the pretzel-shaped synapse and was associated with significantly decreased gastrocnemius, tibialis, and soleus muscle masses.

CONCLUSION

BI induces microglia proliferation and activation (cytokine and chemokine release), degeneration of ventral horn motor neurons and muscle mass loss, all of which were accentuated by concomitant immobilization. The mechanisms connecting microglia activation and motor neuron degeneration to muscle mass loss require further delineation.

Effect of tadalafil on reduction of necrosis in the ischemic zone in a rat comb burn model

OBJECTIVES

A major goal of burn management is to reduce the progression of necrosis in the zone of ischemia surrounding the central zone of necrosis. A rat comb burn model is often used to assess the progression of necrosis in the zone of ischemia. We compared various combinations of naproxen [NPX], N-acetyl cysteine [NAC], and tadalafil [TD] (a phosphodiesterase-5 inhibitor used as a vasodilator to treat erectile dysfunction) in a rat comb burn model to determine their effects on injury progression.

METHODS

We created two comb burns on the backs of 40 anesthetized Sprague-Dawley rats using a brass comb with four rectangular prongs preheated in boiling water and applied for 30s, resulting in four rectangular 10×20mm full-thickness burns separated by three 5×20mm unburned interspaces, representing the ischemic zones. We randomized five animals each to daily oral gavage with TD (1mg/kg), NPX (10mg/kg), NAC (500mg/kg), NAC+NPX, TD+NPX, TD+NAC, TD+NPX+NAC, or normal saline [NS]. Wounds were observed daily for gross evidence of necrosis in the unburned interspaces and full-thickness biopsies from the interspaces were evaluated with Hematoxylin & Eosin seven days after injury for histological evidence of necrosis.

RESULTS

The percentages of interspaces with histological evidence of necrosis at day seven were TD-40%, NPX-93%, NAC-97%, NS-87%, TD+NPX-50%, TD+NAC-40%, TD+NPX+NAC-33%, and NPX+NAC-60% (P<0.001). Repeated measures ANOVA demonstrated reduced gross percentage of interspace area undergoing necrosis in all groups that included TD, compared with all groups not including TD (P<0.001). There were no differences among the various treatments within the groups that did or did not include TD.

CONCLUSIONS

Daily oral therapy with tadalafil reduces necrosis in the unburned interspaces compared with naproxen, NAC, or their combination in a rat comb burn model. Addition of naproxen or NAC to tadalafil does not further reduce injury progression.

Phosphodiesterase 4B knockout prevents skeletal muscle atrophy in rats with burn injury

The phosphodiesterase 4 (PDE4)-cAMP pathway plays a predominant role in mediating skeletal muscle proteolysis in burn injury. The present investigations to determine the PDE4 isoform(s) involved in this action revealed that burn injury increased the expression of rat skeletal muscle PDE4B mRNA by sixfold but had little or no effect on expression of other PDE4 isoforms. These observations led us to study the effects of burn in PDE4B knockout (KO) rats. As reported by us previously, burn injury significantly increased extensor digitorum longus (EDL) muscle total and myofibrillar proteolysis in wild-type (WT) rats, but there were no significant effects on either total or myofibrillar protein breakdown in EDL muscle of PDE4B KO rats with burn injury. Moreover, burn injury increased PDE4 activity in the skeletal muscle of WT rats, but this was reduced by >80% in PDE4B KO rats. Also, burn injury decreased skeletal muscle cAMP concentration in WT rats but had no significant effects in the muscles of PDE4B KO rats. Incubation of the EDL muscle of burn-PDE4B KO rats with an inhibitor of the exchange factor directly activated by cAMP, but not with a protein kinase A inhibitor, eliminated the protective effects of PDE4B KO on EDL muscle proteolysis and increased muscle proteolysis to the same extent as in the EDL of burn-WT rats. These novel findings confirm a major role for PDE4B in skeletal muscle proteolysis in burn injury and suggest that an innovative therapy based on PDE4B-selective inhibitors could be developed to treat skeletal muscle cachexia in burn injury without the fear of causing emesis, which is associated with PDE4D inhibition.

Burns: Pathophysiology of Systemic Complications and Current Management

As a result of many years of research, the intricate cellular mechanisms of burn injury are slowly becoming clear. Yet, knowledge of these cellular mechanisms and a multitude of resulting studies have often failed to translate into improved clinical treatment for burn injuries. Perhaps the most valuable information to date is the years of clinical experience and observations in the management and treatment of patients, which has contributed to a gradual improvement in reported outcomes of mortality. This review provides a discussion of the cellular mechanisms and pathways involved in burn injury, resultant systemic effects on organ systems, current management and treatment, and potential therapies that we may see implemented in the future.

Prevention of Burn-Induced Inflammatory Responses and Muscle Wasting by GTS-21, a Specific Agonist for α7 Nicotinic Acetylcholine Receptors

INTRODUCTION

Muscle wasting (MW) in catabolic conditions (e.g., burn injury [BI]) is a major risk factor affecting prognosis. Activation of interleukin-1β (IL-1β)/nuclear factor-kappa B (NF-κB), interleukin-6 (IL-6)/signal transducer and activator of transcription 3 (STAT3), and/or forkhead box O transcriptional factor (FOXO)-mediated gene transcription pathways is the pivotal trigger of inflammatory response-induced protein catabolic processes in muscle. The α7 acetylcholine receptors (α7AChRs) are upregulated in macrophages and peripheral tissues including skeletal muscle during MW conditions. Stimulation of α7AChRs mitigates inflammatory responses. Hypothesis tested is that attenuation of inflammation by α7AChR stimulation with specific α7AChR agonist, GTS-21, will reverse BI-induced body mass and MW by modulating inflammatory and proteolytic signals.

METHODS

Body surface area (30%) BI or sham BI mice were treated with GTS-21 or saline. Tibialis anterior (TA) muscle was harvested at 6 h, day 1 or 3 to examine inflammatory and proteolytic signals.

RESULTS

GTS-21 significantly ameliorated the BI-induced increased expression of inflammatory cytokines IL-6, IL-1β, C-X-C motif chemokine ligand 2 (6 h), phosphorylated STAT3, and NF-κB (day 1) in TA muscle. GTS-21 also significantly inhibited BI-induced increase of MuRF1 and FOXO1 (day 1). Consistent with the cytokine and inflammatory mediator changes, BI-induced body weight and TA muscle mass loss at day 3 were mitigated by GTS-21 treatment. The beneficial effect of GTS-21 on BI changes was absent in methyllycaconitine (α7AChR antagonist)-treated wild-type and α7AChR knockout mice.

CONCLUSION

GTS-21 stimulation of α7AChRs, by modulating multiple molecular signals related to inflammation and proteolysis, attenuates protein wasting, evidenced by maintenance of body weight and attenuation of distant muscle mass loss after BI. GTS-21 can be a novel, potent therapeutic option for reversal of BI-induced MW.

Amyloid β-induced impairments on mitochondrial dynamics, hippocampal neurogenesis, and memory are restored by phosphodiesterase 7 inhibition

Background

The phosphodiesterase (PDE) 7 inhibitor S14 is a cell-permeable small heterocyclic molecule that is able to cross the blood–brain barrier. We previously found that intraperitoneal treatment with S14 exerted neuroprotection in an Alzheimer’s disease (AD) model (in APP/PS1 mice). The objective of this study was to investigate the neurogenic and cellular effects of oral administration of S14 on amyloid β (Aβ) overload.

Methods

We orally administered the PDE7 inhibitor S14 (15 mg/kg/day) or vehicle in 6-month-old APP/PS1 mice. After 5 weeks of S14 treatment, we evaluated cognitive functions and brain tissues. We also assessed the effects of S14 on the Aβ-treated human neuroblastome SH-SY5Y cell line.

Results

Targeting the cyclic adenosine monophosphate (cAMP)/cAMP-response element binding protein (CREB) pathway, S14 rescued cognitive decline by improving hippocampal neurogenesis in APP/PS1 transgenic mice. Additionally, S14 treatment reverted the Aβ-induced reduction in mitochondrial mass in APP/PS1 mice and in the human neuroblastoma SH-SY5Y cells co-exposed to Aβ. The restoration of the mitochondrial mass was found to be a dual effect of S14: a rescue of the mitochondrial biogenesis formerly slowed down by Aβ overload, and a reduction in the Aβ-increased mitochondrial clearance mechanism of mitophagy.

Conclusions

Here, we show new therapeutic effects of the PDE7 inhibitor, confirming S14 as a potential therapeutic drug for AD.

Electronic supplementary material

The online version of this article (10.1186/s13195-018-0352-4) contains supplementary material, which is available to authorized users.

Role of Elevated Fibrinogen in Burn-Induced Mitochondrial Dysfunction: Protective Effects of Glycyrrhizin

INTRODUCTION

Skeletal muscle wasting and weakness with mitochondrial dysfunction (MD) are major pathological problems in burn injury (BI) patients. Fibrinogen levels elevated in plasma is an accepted risk factor for poor prognosis in many human diseases, and is also designated one of damage-associated molecular pattern (DAMPs) proteins. The roles of upregulated fibrinogen on muscle changes of critical illness including BI are unknown. The hypothesis tested was that BI-upregulated fibrinogen plays a pivotal role in the inflammatory responses and MD in muscles, and that DAMPs inhibitor, glycyrrhizin mitigates the muscle changes.

METHODS

After third degree BI to mice, fibrinogen levels in the plasma and at skeletal muscles were compared between BI and sham-burn (SB) mice. Fibrinogen effects on inflammatory responses and mitochondrial membrane potential (MMP) loss were analyzed in C2C12 myotubes. In addition to survival, the anti-inflammatory and mitochondrial protective effects of glycyrrhizin were tested using in vivo microscopy of skeletal muscles of BI and SB mice.

RESULTS

Fibrinogen in plasma and its extravasation to muscles significantly increased in BI versus SB mice. Fibrinogen applied to myotubes evoked inflammatory responses (increased MCP-1 and TNF-α; 32.6 and 3.9-fold, respectively) and reduced MMP; these changes were ameliorated by glycyrrhizin treatment. In vivo MMP loss and superoxide production in skeletal muscles of BI mice were significantly attenuated by glycyrrhizin treatment, together with improvement of BI survival rate.

CONCLUSIONS

Inflammatory responses and MMP loss in myotubes induced by fibrinogen were reversed by glycyrrhizin. Anti-inflammatory and mitochondrial protective effect of glycyrrhizin in vivo leads to amelioration of muscle MD and improvement of BI survival rate.

Formoterol decreases muscle wasting as well as inflammation in the rat model of rheumatoid arthritis

Adjuvant-induced arthritis is an experimental model of rheumatoid arthritis that is associated with body weight loss and muscle wasting. β2-adrenergic receptor agonists are powerful anabolic agents that trigger skeletal muscle hypertrophy and have been proposed as a promising treatment for muscle wasting in human patients. The aim of this work was to determine whether formoterol, a selective β2-adrenoreceptor agonist, is able to ameliorate muscle wasting in arthritic rats. Arthritis was induced in male Wistar rats by intradermal injection of Freund's adjuvant. Control and arthritic rats were injected daily with 50 μg/kg sc formoterol or saline for 12 days. Body weight change, food intake, and arthritis index were analyzed. After euthanasia, in the gastrocnemius mRNA was analyzed by PCR, and proteins were analyzed by Western blotting. Arthritis decreased gastrocnemius weight, cross-sectional area, and myofiber size, whereas formoterol increased those variables in both arthritic and control rats. Formoterol decreased the external signs of arthritis as well as NF-κB(p65) activation, TNFα, and COX-2 levels in the gastrocnemius of arthritic and control rats. Those effects of formoterol were associated with a decreased expression of myostatin, atrogin-1, and MuRF1 and in LC3b lipidation. Arthritis increased the expression of MyoD, myogenin, IGF-I, and IGFBP-3 and -5 in the gastrocnemius. In control and in arthritic rats, treatment with formoterol increased Akt phosphorylation and myogenin levels, whereas it decreased IGFBP-3 expression in the gastrocnemius. These data suggest that formoterol has an anti-inflammatory effect and decreases muscle wasting in arthritic rats through increasing Akt activity and myogenin and decreasing myostatin, the p-NF-κB(p65)/TNF pathway, and IGFBP-3.

MITOCHONDRIAL FUNCTION IN SEPSIS

Mitochondria are an essential part of the cellular infrastructure, being the primary site for high-energy adenosine triphosphate production through oxidative phosphorylation. Clearly, in severe systemic inflammatory states, like sepsis, cellular metabolism is usually altered, and end organ dysfunction is not only common, but also predictive of long-term morbidity and mortality. Clearly, interest is mitochondrial function both as a target for intracellular injury and response to extrinsic stress have been a major focus of basic science and clinical research into the pathophysiology of acute illness. However, mitochondria have multiple metabolic and signaling functions that may be central in both the expression of sepsis and its ultimate outcome. In this review, the authors address five primary questions centered on the role of mitochondria in sepsis. This review should be used both as a summary source in placing mitochondrial physiology within the context of acute illness and as a focal point for addressing new research into diagnostic and treatment opportunities these insights provide.

The melanocortin receptor type 3 agonist d-Trp(8)-γMSH decreases inflammation and muscle wasting in arthritic rats

BACKGROUND

Chronic inflammatory diseases induce cachexia that increases mortality and morbidity of the illness. Adjuvant-induced arthritis is an experimental model of rheumatoid arthritis that is associated with body weight loss and muscle wasting. Alpha-melanocyte stimulating hormone has an anti-inflammatory effect in arthritic rats and decreases muscle wasting. The aim of this work was to elucidate whether the anti-cachectic action of alpha-melanocyte stimulating hormone is mediated by the melanocortin receptor type 3 pathway.

METHODS

Arthritis was induced in male Wistar rats by intradermal injection of Freund's adjuvant, and 6 days afterwards, arthritic rats were injected with the selective melanocortin receptor type 3 agonist d-Trp(8)-gammaMSH ( d-Trp(8)-γMSH) 500 µg/kg subcutaneously. or saline twice a day, for 10 days.

RESULTS

d-Trp(8)-γMSH decreased the external signs of inflammation and body weight loss, but it was not able to modify the anorexigenic effect of arthritis or the increase in hypothalamic cyclooxygenase-2 (COX-2) expression. In contrast, d-Trp(8)-γMSH prevented arthritis-induced increase in hypothalamic IL-1β and serum corticosterone levels and the decrease in serum IGF-I levels. d-Trp(8)-γMSH treatment also prevented arthritis-induced NF-kB(p65) phosphorylation and tumour necrosis factor-α mRNA increase in the gastrocnemius. d-Trp(8)-γMSH administration to arthritic rats increased gastrocnemius mass, its cross-sectional area, and mean fast fibre area. Those effects of d-Trp(8)-γMSH were associated with a decreased expression of atrogin-1 and muscle ring-finger protein-1 in the gastrocnemius. In rats treated with saline, arthritis increased the expression of autophagy marker genes LC3b, Bnip-3, and Gabarap1 as well as the conversion of LC3b I to LC3b II by lipidation in the gastrocnemius. d-Trp(8)-γMSH decreased gastrocnemius LC3b, Bnip-3, and Gabarap1 mRNA expression and prevented the increase in LC3b II in arthritic rats.

CONCLUSION

These data suggest that d-Trp(8)-γMSH administration prevents the effect of arthritis on corticosterone and insulin-like growth factor-I serum levels and decreases muscle wasting, by down-regulating atrogenes and autophagy through modifying the NF-kB(p65)/tumour necrosis factor-α signalling transduction pathway.

Bacterial-excreted small volatile molecule 2-aminoacetophenone induces oxidative stress and apoptosis in murine skeletal muscle

Oxidative stress induces mitochondrial dysfunction and facilitates apoptosis, tissue damage or metabolic alterations following infection. We have previously discovered that the Pseudomonas aeruginosa (PA) quorum sensing (QS)-excreted small volatile molecule, 2-aminoacetophenone (2-AA), which is produced in infected human tissue, promotes bacterial phenotypes that favor chronic infection, while also compromising muscle function and dampens the pathogen-induced innate immune response, promoting host tolerance to infection. In this study, murine whole-genome expression data have demonstrated that 2-AA affects the expression of genes involved in reactive oxygen species (ROS) homeostasis, thus producing an oxidative stress signature in skeletal muscle. The results of the present study demonstrated that the expression levels of genes involved in apoptosis signaling pathways were upregulated in the skeletal muscle of 2-AA-treated mice. To confirm the results of our transcriptome analysis, we used a novel high-resolution magic-angle-spinning (HRMAS), proton (¹H) nuclear magnetic resonance (NMR) method and observed increased levels of bisallylic methylene fatty acyl protons and vinyl protons, suggesting that 2-AA induces skeletal muscle cell apoptosis. This effect was corroborated by our results demonstrating the downregulation of mitochondrial membrane potential in vivo in response to 2-AA. The findings of the present study indicate that the bacterial infochemical, 2-AA, disrupts mitochondrial functions by inducing oxidative stress and apoptosis signaling and likely promotes skeletal muscle dysfunction, which may favor chronic/persistent infection.

Heat shock response and autophagy--cooperation and control

Protein quality control (proteostasis) depends on constant protein degradation and resynthesis, and is essential for proper homeostasis in systems from single cells to whole organisms. Cells possess several mechanisms and processes to maintain proteostasis. At one end of the spectrum, the heat shock proteins modulate protein folding and repair. At the other end, the proteasome and autophagy as well as other lysosome-dependent systems, function in the degradation of dysfunctional proteins. In this review, we examine how these systems interact to maintain proteostasis. Both the direct cellular data on heat shock control over autophagy and the time course of exercise-associated changes in humans support the model that heat shock response and autophagy are tightly linked. Studying the links between exercise stress and molecular control of proteostasis provides evidence that the heat shock response and autophagy coordinate and undergo sequential activation and downregulation, and that this is essential for proper proteostasis in eukaryotic systems.

Anesthesia with Disuse Leads to Autophagy Up-regulation in the Skeletal Muscle

BACKGROUND

It has been known that skeletal muscles show atrophic changes after prolonged sedation or general anesthesia. Whether these effects are due to anesthesia itself or disuse during anesthesia has not been fully clarified. Autophagy dysregulation has been implicated in muscle-wasting conditions. This study tested the hypothesis that the magnitude of skeletal muscle autophagy is affected by both anesthesia and immobility.

METHODS

The extent of autophagy was analyzed chronologically during general anesthesia. In vivo microscopy was performed using green fluorescent protein-tagged LC3 for the detection of autophagy using sternomastoid muscles of live mice during pentobarbital anesthesia (n = 6 and 7). Western blotting and histological analyses were also conducted on tibialis anterior muscles (n = 3 to 5). To distinguish the effect of anesthesia from that due to disuse, autophagy was compared between animals anesthetized with pentobarbital and those immobilized by short-term denervation without continuation of anesthesia. Conversely, tibialis anterior and sternomastoid muscles were electrically stimulated during anesthesia.

RESULTS

Western blots and microscopy showed time-dependent autophagy up-regulation during pentobarbital anesthesia, peaking at 3 h (728.6 ± 93.5% of basal level, mean ± SE). Disuse by denervation without sustaining anesthesia did not lead to equivalent autophagy, suggesting that anesthesia is essential to cause autophagy. In contrast, contractile stimulation of the tibialis anterior and sternomastoid muscles significantly reduced the autophagy up-regulation during anesthesia (85% at 300 min). Ketamine, ketamine plus xylazine, isoflurane, and propofol also up-regulated autophagy.

CONCLUSIONS

Short-term disuse without anesthesia does not lead to autophagy, but anesthesia with disuse leads to marked up-regulation of autophagy.

The Sick and the Weak: Neuropathies/Myopathies in the Critically Ill

Critical illness polyneuropathies (CIP) and myopathies (CIM) are common complications of critical illness. Several weakness syndromes are summarized under the term intensive care unit-acquired weakness (ICUAW). We propose a classification of different ICUAW forms (CIM, CIP, sepsis-induced, steroid-denervation myopathy) and pathophysiological mechanisms from clinical and animal model data. Triggers include sepsis, mechanical ventilation, muscle unloading, steroid treatment, or denervation. Some ICUAW forms require stringent diagnostic features; CIM is marked by membrane hypoexcitability, severe atrophy, preferential myosin loss, ultrastructural alterations, and inadequate autophagy activation while myopathies in pure sepsis do not reproduce marked myosin loss. Reduced membrane excitability results from depolarization and ion channel dysfunction. Mitochondrial dysfunction contributes to energy-dependent processes. Ubiquitin proteasome and calpain activation trigger muscle proteolysis and atrophy while protein synthesis is impaired. Myosin loss is more pronounced than actin loss in CIM. Protein quality control is altered by inadequate autophagy. Ca(2+) dysregulation is present through altered Ca(2+) homeostasis. We highlight clinical hallmarks, trigger factors, and potential mechanisms from human studies and animal models that allow separation of risk factors that may trigger distinct mechanisms contributing to weakness. During critical illness, altered inflammatory (cytokines) and metabolic pathways deteriorate muscle function. ICUAW prevention/treatment is limited, e.g., tight glycemic control, delaying nutrition, and early mobilization. Future challenges include identification of primary/secondary events during the time course of critical illness, the interplay between membrane excitability, bioenergetic failure and differential proteolysis, and finding new therapeutic targets by help of tailored animal models.

Tadalafil therapy and severe chronic foot wound resolution

We report an unanticipated medication effect resulting in near-complete wound healing in a patient after beginning tadalafil therapy of 20 mg thrice daily. This patient was treated for 50 years with state-of-the art acute and then chronic wound interventions after a traumatic farm machinery accident which resulted in a devascularised foot wound. This infection was both life- and limb-threatening. The patient had undergone multiple vascular and plastic surgeries and antimicrobial therapies in addition to hospitalisations for sepsis. Limb amputation was being considered, when his urologist placed him on daily phosphodiesterase-5 inhibitor therapy, prior to unrelated urologic surgery. Remarkably, his foot wound underwent near-complete resolution and has been stable for 2 years.

Coming back: autophagy in cachexia

PURPOSE OF REVIEW

Cachexia is a complex syndrome characterized by body weight loss, tissue wasting, systemic inflammation, metabolic abnormalities, and altered nutritional status. One of the most prominent features of cachexia is the loss of muscle mass, mainly because of increased protein degradation rates. This review is aimed at discussing the involvement of autophagy in the pathogenesis of muscle wasting in cachexia.

RECENT FINDINGS

Modulations of muscle mass in the adult reflect an imbalance between protein synthesis and degradation rates. Muscle depletion in cachexia is associated with increased protein breakdown, mainly involving the pathways dependent on ubiquitin-proteasome and autophagy-lysosomes. This latter, in particular, was considered not relevant for a long time. Just in the last years, autophagy was shown to contribute to the pathogenesis of muscle wasting not only in myopathies because of intrinsic muscle defects, but also in muscle depletion associated with conditions such as sepsis, chronic obstructive pulmonary disease, glucocorticoid treatment, cancer cachexia, and aging.

SUMMARY

The present review highlights that both excess and defective autophagy are relevant to the onset of muscle depletion, and draws some considerations about possible therapeutic intervention aimed at modulating autophagy in order to improve muscle trophism.

VIDEO ABSTRACT

http://links.lww.com/COCN/A5.