Approach to traumatic cardiac arrest in the emergency department: a narrative literature review for emergency providers.

BACKGROUND: Traumatic cardiac arrest (TCA) is a major contributor to mortality and morbidity in all age groups and poses a significant burden on the healthcare system. Although there have been advances in treatment modalities, survival rates for TCA patients remain low. This narrative literature review critically examines the indications and effectiveness of current therapeutic approaches in treating TCA. METHODS: We performed a literature search in the PubMed and Scopus databases for studies published before December 31, 2022. The search was refined by combining search terms, examining relevant study references, and restricting publications to the English language. Following the search, 943 articles were retrieved, and two independent reviewers conducted a screening process. RESULTS: A review of various studies on pre- and intra-arrest prognostic factors showed that survival rates were higher when patients had an initial shockable rhythm. There were conflicting results regarding other prognostic factors, such as witnessed arrest, bystander cardiopulmonary resuscitation (CPR), and the use of prehospital or in-hospital epinephrine. Emergency thoracotomy was found to result in more favorable outcomes in cases of penetrating trauma than in those with blunt trauma. Resuscitative endovascular balloon occlusion of the aorta (REBOA) provides an advantage to emergency thoracotomy in terms of occupational safety for the operator as an alternative in managing hemorrhagic shock. When implemented in the setting of aortic occlusion, emergency thoracotomy and REBOA resulted in comparable mortality rates. Veno-venous extracorporeal life support (V-V ECLS) and veno-arterial extracorporeal life support (V-A ECLS) are viable options for treating respiratory failure and cardiogenic shock, respectively. In the context of traumatic injuries, V-V ECLS has been associated with higher rates of survival to discharge than V-A ECLS. CONCLUSION: TCA remains a significant challenge for emergency medical services due to its high morbidity and mortality rates. Pre- and intra-arrest prognostic factors can help identify patients who are likely to benefit from aggressive and resource-intensive resuscitation measures. Further research is needed to enhance guidelines for the clinical use of established and emerging therapeutic approaches that can help optimize treatment efficacy and ameliorate survival outcomes.

0.05% Chlorhexidine Gluconate Irrigation in Trauma/Emergency General Surgical Laparotomy Wounds Closure: A Pilot Study.

INTRODUCTION: Patients who undergo exploratory laparotomy (EL) in an emergent setting are at higher risk for surgical site infections (SSIs) compared to the elective setting. Packaged Food and Drug Administration-approved 0.05% chlorhexidine gluconate (CHG) irrigation solution reduces SSI rates in nonemergency settings. We hypothesize that the use of 0.05% CHG irrigation solution prior to closure of emergent EL incisions will be associated with lower rates of superficial SSI and allows for increased rates of primary skin closure. METHODS: A retrospective observational study of all emergent EL whose subcutaneous tissue were irrigated with 0.05% CHG solution to achieve primary wound closure from March 2021 to June 2022 were performed. Patients with active soft-tissue infection of the abdominal wall were excluded. Our primary outcome is rate of primary skin closure following laparotomy. Descriptive statistics, including t-test and chi-square test, were used to compare groups as appropriate. A P value <0.05 was statistically significant. RESULTS: Sixty-six patients with a median age of 51 y (18-92 y) underwent emergent EL. Primary wound closure is achieved in 98.5% of patients (65/66). Bedside removal of some staples and conversion to wet-to-dry packing changes was required in 27.3% of patients (18/66). We found that most of these were due to fat necrosis. We report no cases of fascial dehiscence. CONCLUSIONS: In patients undergoing EL, intraoperative irrigation of the subcutaneous tissue with 0.05% CHG solution is a viable option for primary skin closure. Further studies are needed to prospectively evaluate our findings.

Development and Validation of a Novel Hollow Viscus Injury Prediction Score for Abdominal Seatbelt Sign: A Pacific Coast Surgical Association Multicenter Study.

BACKGROUND: High-quality CT can exclude hollow viscus injury (HVI) in patients with abdominal seatbelt sign (SBS) but performs poorly at identifying HVI. Delay in diagnosis of HVI has significant consequences necessitating timely identification. STUDY DESIGN: This multicenter, prospective observational study conducted at 9 trauma centers between August 2020 and October 2021 included adult trauma patients with abdominal SBS who underwent abdominal CT before surgery. HVI was determined intraoperatively and physiologic, examination, laboratory, and imaging findings were collected. Least absolute shrinkage and selection operator- and probit regression-selected predictor variables and coefficients were used to assign integer points for the HVI score. Validation was performed by comparing the area under receiver operating curves (AUROC). RESULTS: Analysis included 473 in the development set and 203 in the validation set. The HVI score includes initial systolic blood pressure <110 mmHg, abdominal tenderness, guarding, and select abdominal CT findings. The derivation set has an AUROC of 0.96, and the validation set has an AUROC of 0.91. The HVI score ranges from 0 to 17 with score 0 to 5 having an HVI risk of 0.03% to 5.36%, 6 to 9 having a risk of 10.65% to 44.1%, and 10 to 17 having a risk of 58.59% to 99.72%. CONCLUSIONS: This multicenter study developed and validated a novel HVI score incorporating readily available physiologic, examination, and CT findings to risk stratify patients with an abdominal SBS. The HVI score can be used to guide decisions regarding management of a patient with an abdominal SBS and suspected HVI.

Racial Disparities in Administration of Venous Thromboembolism Prophylaxis After Severe Traumatic Injuries.

BACKGROUND: Race is associated with differences in quality of care process measures and incidence of venous thromboembolism (VTE) in trauma patients. We aimed to investigate if racial disparities exist in the administration of VTE prophylaxis in trauma patients. METHODS: We queried the Trauma Quality Improvement Project database from 2017 to 2019. Patients ages ≥16 years old with ISS ≥15 were included. Patients with no signs of life on arrival, any AIS ≥6, hospital length of stay <1 day, anticoagulant use before admission, or without recorded race were excluded. Patients were grouped by race: white, black, Asian, American Indian, and Native Hawaiian or Pacific Islander. The association between VTE prophylaxis administration and race was determined using a Poisson regression model with robust standard errors to adjust for confounders. RESULTS: A total of 285,341 patients were included. Black patients had the highest rates of VTE prophylaxis exposure (73.8%), shortest time to administration (1.6 days), and highest use of low molecular weight heparin (56%). Black patients also had the highest incidence of deep vein thrombosis (2.8%) and pulmonary embolism (1.4%). Black patients were 4% more likely to receive VTE prophylaxis than white patients [adj. IRR (95% CI): 1.04 (1.03-1.05), P < .001]. American Indians were 8% less likely to receive VTE prophylaxis [adj. IRR (95% CI): .92 (.88-.97), P < .001] than white patients. No differences between white and Asian or Native Hawaiian or Pacific Islander patients existed. DISCUSSION: While black patients had the highest incidence of DVT and PE, they had higher administration rates and earlier initiation of VTE prophylaxis. Further work can elucidate modifiable causes of these differences.

Two Urgency Categories, Same Outcome: No Difference After "Therapeutic" vs. "Prophylactic" Fasciotomy.

OBJECTIVES: Fasciotomy to treat or prevent compartment syndromes in patients with truncal or peripheral arterial injuries is a valuable adjunct. The objective of this study was to document the current incidence, indications, and outcomes of below knee fasciotomy in patients with femoropopliteal arterial injuries. METHODS: The PROspective Observational Vascular Injury Treatment registry of the American Association for the Surgery of Trauma was utilized to identify patients undergoing two-incision four-compartment fasciotomy of the leg after repair of a femoropopliteal arterial injury. Outcomes after therapeutic versus prophylactic (surgeon label) fasciotomy were compared as was the technique of closure, that is, primary skin closure or application of a split-thickness skin graft (STSG). RESULTS: From 2013 to 2018, fasciotomy was performed in 158 patients overall, including 95.6% (151/158) at the initial operation. In the group of 139 patients who survived to discharge, fasciotomies were labeled as therapeutic in 58.3% (81/139) and prophylactic in 41.7% (58/139). There were no significant differences between the therapeutic and prophylactic groups in amputation rates (14.8% vs. 8.6%, P = .919). Primary skin closure was achieved at a median of 5.0 days vs. 11.0 days for STSG (P = .001). CONCLUSIONS: Over 55% of patients undergoing repair of an injury to a femoral or popliteal artery have a fasciotomy performed at the same operation. A "therapeutic" indication for fasciotomy continues to be more common than "prophylactic," while outcomes are identical in both groups.

Contemporary Management of Traumatic Duodenal Injuries.

BACKGROUND: Traumatic duodenal injury is a rare, potentially devastating condition with challenging management decisions. Contemporary literature on operative management of duodenal injury is lacking. The purpose of this study is to assess optimal management strategies based on outcomes of patients with traumatic duodenal injury at a single trauma center. METHODS: A retrospective study of patients with traumatic duodenal injury from 2013-2020 at a level 1 trauma center was performed. Patient demographics, grade of injury as noted on CT scan or intraoperatively, surgical procedure(s) performed, and resultant outcomes were extracted. RESULTS: After excluding one patient due to death on arrival, 23 patients met inclusion criteria. Injuries consisted of grade 1 (n = 7), grade 2 (n = 2), grade 3 (n = 12), and grade 5 (n = 2); there were no grade 4 injuries. Patients were predominantly male (83%) with a median age of 30 years old. Nineteen patients (82%) underwent surgery. Four of nine patients (44%) with grade 1/2 injuries had hematomas and were managed non-operatively. The remaining five patients (56%) with grade 1/2 injuries underwent operation, which included primary repair (n = 3), duodenal exclusion (n = 1), and periduodenal drainage (n = 1). Of 12 patients with grade 3 injury, 6 underwent primary repair and 6 underwent resection. Three patients who underwent primary repair and one who underwent resection developed a duodenal leak. All patients with grade 5 injury (n = 2) underwent pancreaticoduodenectomy. CONCLUSION: Grade 1 and 2 duodenal hematomas can be managed non-operatively, while lacerations require operative repair. Outcomes may be better following resection in patients with grade 3 injury.

Excluding Hollow Viscus Injury for Abdominal Seat Belt Sign Using Computed Tomography.

Importance: Abdominal seat belt sign (SBS) has historically entailed admission and observation because of the diagnostic limitations of computed tomography (CT) imaging and high rates of hollow viscus injury (HVI). Recent single-institution, observational studies have questioned the utility of this practice. Objective: To evaluate whether a negative CT scan can safely predict the absence of HVI in the setting of an abdominal SBS. Design, Setting, and Participants: This prospective, observational cohort study was conducted in 9 level I trauma centers between August 2020 and October 2021 and included adult trauma patients with abdominal SBS. Exposures: Inclusion in the study required abdominal CT as part of the initial trauma evaluation and before any surgical intervention, if performed. Results of CT scans were considered positive if they revealed any of the following: abdominal wall soft tissue contusion, free fluid, bowel wall thickening, mesenteric stranding, mesenteric hematoma, bowel dilation, pneumatosis, or pneumoperitoneum. Main Outcomes and Measures: Presence of HVI diagnosed at the time of operative intervention. Results: A total of 754 patients with abdominal SBS had an HVI prevalence of 9.2% (n = 69), with only 1 patient with HVI (0.1%) having a negative CT (ie, none of the 8 a priori CT findings). On bivariate analysis comparing patients with and without HVI, there were significant associations between each of the individual CT scan findings and the presence of HVI. The strongest association was found with the presence of free fluid, with a more than 40-fold increase in the likelihood of HVI (odds ratio [OR], 42.68; 95% CI, 20.48-88.94; P < .001). The presence of free fluid also served as the most effective binary classifier for presence of HVI (area under the receiver operator characteristic curve [AUC], 0.87; 95% CI, 0.83-0.91). There was also an association between a negative CT scan and the absence of HVI (OR, 41.09; 95% CI, 9.01-727.69; P < .001; AUC, 0.68; 95% CI, 0.66-0.70). Conclusions and Relevance: The prevalence of HVI among patients with an abdominal SBS and negative findings on CT is extremely low, if not zero. The practice of admitting and observing all patients with abdominal SBS should be reconsidered when a high-quality CT scan is negative, which may lead to significant resource and cost savings.

Cresting mortality: Defining a plateau in ongoing massive transfusion.

BACKGROUND: Blood-based balanced resuscitation is a standard of care in massively bleeding trauma patients. No data exist as to when this therapy no longer significantly affects mortality. We sought to determine if there is a threshold beyond which further massive transfusion will not affect in-hospital mortality. METHODS: The Trauma Quality Improvement database was queried for all adult patients registered between 2013 and 2017 who received at least one unit of blood (packed red blood cell) within 4 hours of arrival. In-hospital mortality was evaluated based on the total transfusion volume (TTV) at 4 hours and 24 hours in the overall cohort (OC) and in a balanced transfusion cohort, composed of patients who received transfusion at a ratio of 1:1 to 2:1 packed red blood cell to plasma. A bootstrapping method in combination with multivariable Poisson regression was used to find a cutoff after which additional transfusion no longer affected in-hospital mortality. Multivariable Poisson regression was used to control for age, sex, race, highest Abbreviated Injury Scale score in each body region, comorbidities, advanced directives limiting care, and the primary surgery performed for hemorrhage control. RESULTS: The OC consisted of 99,042 patients, of which 28,891 and 30,768 received a balanced transfusion during the first 4 hours and 24 hours, respectively. The mortality rate plateaued after a TTV of 40.5 units (95% confidence interval [CI], 40-41) in the OC at 4 hours and after a TTV of 52.8 units (95% CI, 52-53) at 24 hours following admission. In the balanced transfusion cohort, mortality plateaued at a TTV of 39 units (95% CI, 39-39) and 53 units (95% CI, 53-53) at 4 hours and 24 hours following admission, respectively. CONCLUSION: Transfusion thresholds exist beyond which ongoing transfusion is not associated with any clinically significant change in mortality. These TTVs can be used as markers for resuscitation timeouts to assess the plan of care moving forward. LEVEL OF EVIDENCE: Prognostic and epidemiological, Level III.

Association of Early Aspirin Use With In-Hospital Mortality in Patients With Moderate COVID-19.

Importance: Prior observational studies suggest that aspirin use may be associated with reduced mortality in high-risk hospitalized patients with COVID-19, but aspirin's efficacy in patients with moderate COVID-19 is not well studied. Objective: To assess whether early aspirin use is associated with lower odds of in-hospital mortality in patients with moderate COVID-19. Design, Setting, and Participants: Observational cohort study of 112 269 hospitalized patients with moderate COVID-19, enrolled from January 1, 2020, through September 10, 2021, at 64 health systems in the United States participating in the National Institute of Health's National COVID Cohort Collaborative (N3C). Exposure: Aspirin use within the first day of hospitalization. Main Outcome and Measures: The primary outcome was 28-day in-hospital mortality, and secondary outcomes were pulmonary embolism and deep vein thrombosis. Odds of in-hospital mortality were calculated using marginal structural Cox and logistic regression models. Inverse probability of treatment weighting was used to reduce bias from confounding and balance characteristics between groups. Results: Among the 2 446 650 COVID-19-positive patients who were screened, 189 287 were hospitalized and 112 269 met study inclusion. For the full cohort, Median age was 63 years (IQR, 47-74 years); 16.1% of patients were African American, 3.8% were Asian, 52.7% were White, 5.0% were of other races and ethnicities, 22.4% were of unknown race and ethnicity. In-hospital mortality occurred in 10.9% of patients. After inverse probability treatment weighting, 28-day in-hospital mortality was significantly lower in those who received aspirin (10.2% vs 11.8%; odds ratio [OR], 0.85; 95% CI, 0.79-0.92; P < .001). The rate of pulmonary embolism, but not deep vein thrombosis, was also significantly lower in patients who received aspirin (1.0% vs 1.4%; OR, 0.71; 95% CI, 0.56-0.90; P = .004). Patients who received early aspirin did not have higher rates of gastrointestinal hemorrhage (0.8% aspirin vs 0.7% no aspirin; OR, 1.04; 95% CI, 0.82-1.33; P = .72), cerebral hemorrhage (0.6% aspirin vs 0.4% no aspirin; OR, 1.32; 95% CI, 0.92-1.88; P = .13), or blood transfusion (2.7% aspirin vs 2.3% no aspirin; OR, 1.14; 95% CI, 0.99-1.32; P = .06). The composite of hemorrhagic complications did not occur more often in those receiving aspirin (3.7% aspirin vs 3.2% no aspirin; OR, 1.13; 95% CI, 1.00-1.28; P = .054). Subgroups who appeared to benefit the most included patients older than 60 years (61-80 years: OR, 0.79; 95% CI, 0.72-0.87; P < .001; >80 years: OR, 0.79; 95% CI, 0.69-0.91; P < .001) and patients with comorbidities (1 comorbidity: 6.4% vs 9.2%; OR, 0.68; 95% CI, 0.55-0.83; P < .001; 2 comorbidities: 10.5% vs 12.8%; OR, 0.80; 95% CI, 0.69-0.93; P = .003; 3 comorbidities: 13.8% vs 17.0%, OR, 0.78; 95% CI, 0.68-0.89; P < .001; >3 comorbidities: 17.0% vs 21.6%; OR, 0.74; 95% CI, 0.66-0.84; P < .001). Conclusions and Relevance: In this cohort study of US adults hospitalized with moderate COVID-19, early aspirin use was associated with lower odds of 28-day in-hospital mortality. A randomized clinical trial that includes diverse patients with moderate COVID-19 is warranted to adequately evaluate aspirin's efficacy in patients with high-risk conditions.

Attending guidance advised: educational quality of surgical videos on YouTube.

INTRODUCTION: YouTube is the most used platform for case preparation by surgical trainees. Despite its popular use, studies have noted limitations in surgical technique, safety, and vetting of these videos. This study identified the most viewed laparoscopic cholecystectomy (LC) videos on YouTube and analyzed the ability of attendings, residents, and medical students to identify critical portions of the procedure, technique, and limitations of the videos. METHODS: An incognito search was conducted on YouTube using the term "laparoscopic cholecystectomy." Results were screened for length, publication date, and language. The top ten most viewed videos were presented to general surgery attendings, residents, and medical students at a single academic institution. Established rubrics were used for evaluation, including the Critical View of Safety (CVS) for LC, a modified Global Operative Assessment of Laparoscopic Skills (GOALS) score, a task-specific checklist, and visual analog scales for case difficulty and operator competence. Educational quality and likelihood of video recommendation for case preparation were evaluated using a Likert scale. Attending assessments were considered the gold standard. RESULTS: Six attending surgeons achieved excellent internal consistency on CVS, educational quality, and likelihood of recommendation scales, with Cronbach alpha (⍺) of 0.93, 0.92, and 0.92, respectively. ⍺ was ≥ 0.7 in all the other scales measured. Attending evaluations revealed that only one of the ten videos attained all three established CVS criteria. Four videos demonstrated none of the CVS criteria. The mean educational quality (mEQ) was 4.63 on a 10-point scale. The mean likelihood of recommendation (mLoR) for case preparation was 2.3 on a 5-point scale. Senior resident assessments (Postgraduate Year (PGY)4 + , n = 12) aligned with attending surgeons, with no statistically significant differences in CVS attainment, mEQ, and mLoR. Junior residents (PGY1-3, n = 17) and medical students (MS3-4, n = 20) exhibited significant difference with attendings in CVS attainment, mEQ, and mLoR for more than half the videos. Both groups tended to overrate videos compared to attendings. CONCLUSION: YouTube is the most popular unvetted resource used for case presentation by surgical trainees. Attending evaluations revealed that the most viewed LC videos on YouTube did not attain the CVS, and were deemed as inappropriate for case preparation, with low educational value. Senior resident video assessments closely aligned with attendings, while junior trainees were more likely to overstate video quality and value. Attending guidance and direction of trainees to high-quality, vetted resources for surgical case preparation is needed. This may also suggest a need for surgical societies with platforms for video sharing to prioritize the creation and dissemination of high-quality videos on easily accessible public platforms.

A Retrospective Study of Infection in Patients Requiring Extracorporeal Membrane Oxygenation Support.

BACKGROUND: Healthcare-associated infections (HAIs) in critically ill patients are a serious public health problem. Extracorporeal membrane oxygenation (ECMO) has been used increasingly for patients with severe cardiac or respiratory failure, but it may increase HAI risk. The goal of our study was to characterize HAIs in ECMO patients at an ECMO referral center. METHODS: This institutional review board-approved study identified all consecutive adult ECMO patients admitted to the cardiac surgery intensive care unit (CSICU) between January 1, 2015, and December 31, 2017. Demographic data, diagnosis, ECMO cannulation technique, and survival were collected. Urinary tract infection, pneumonia, and bacteremia incidence during ECMO and within 3 months of decannulation were collected. Outcomes of patients with HAIs were compared with noninfected patients, the CSICU infection incidence, and overall Extracorporeal Life Support Organization survival data. RESULTS: There were 288 ECMO patients and 3396 CSICU admissions during this period. Survival was 72.3% for venoarterial ECMO, 85.3% for venovenous ECMO, and 57.1% for multimodality or veno-arteriovenous ECMO, with discharge survival of 60.2%, 72.0%, and 28.6%, respectively. Bacteremia incidence while cannulated was 6.8% for venoarterial ECMO and 9.3% for venovenous ECMO. Bacteremia occurred in 22 of 288 (7.6%) ECMO patients, compared with 48 of 3109 (1.5%) in non-ECMO CSICU patients, which was statistically significant (P < .002). Bacteremia and pneumonia were associated with decreased VA-ECMO survival, with prolonged overall requirements for ECMO support. CONCLUSIONS: Nosocomial ECMO infections are significantly higher than in other CSICU patients. Infection risk remains significant even after decannulation. Infection is associated with increased mortality and longer duration of ECMO support. Further efforts are needed to determine HAI reduction strategies in this high-risk patient population.

A Multi-Institutional Analysis of Damage Control Laparotomy in Elderly Trauma Patients: Do Geriatric Trauma Protocols Matter?

BACKGROUND: Trauma centers are receiving increasing numbers of older trauma patients. There is a lack of literature on the outcomes for elderly trauma patients who undergo damage control laparotomy (DCL). We hypothesized that trauma centers with geriatric protocols would have better outcomes in elderly patients after DCL. METHODS: A retrospective chart review of consecutive adult trauma patients with DCL at 8 level 1 trauma centers was conducted from 2012 to 2018. Patients aged 40 or older were included. Age ≥ 55 years was defined as elderly. Demographics, injury information, clinical outcomes, including mortality, and complications were recorded. Univariate and multivariate analyses were performed. RESULTS: A total of 379 patients with DCLs were identified with an average age of 54.8 ± 0.4 years with 39.3% (n = 149/379) of patients aged ≥ 55. Geriatric protocols or a consulting geriatric service was present at 37.5% (n = 3/8) of institutions. Age ≥ 55 was a significant risk factor for in-hospital mortality (OR 2, 95% CI 1.0-4.0, P = .04). Institutions without dedicated geriatric trauma protocols/services had higher overall in-hospital mortality on both univariate (57.9% vs 34.3%, P = .02) and multivariate analyses (OR 2.1, 95% CI 1.3-3.4, P < .001). CONCLUSIONS: Surgical management of older trauma patients remains a challenge. Geriatric protocols or dedicated services were found to be associated with improved outcomes. Future efforts should focus on standardizing the availability of these resources at trauma centers.

Cessation of biomechanical stretch model of C2C12 cells models myocyte atrophy and anaplerotic changes in metabolism using non-targeted metabolomics analysis.

Studies of skeletal muscle disuse, either in patients on bed rest or experimentally in animals (immobilization), have demonstrated that decreased protein synthesis is common, with transient parallel increases in protein degradation. Muscle disuse atrophy involves a process of transition from slow to fast myosin fiber types. A shift toward glycolysis, decreased capacity for fat oxidation, and substrate accumulation in atrophied muscles have been reported, as has accommodation of the liver with an increased gluconeogenic capacity. Recent studies have modeled skeletal muscle disuse by using cyclic stretch of differentiated myotubes (C2C12), which mimics the loading pattern of mature skeletal muscle, followed by cessation of stretch. We utilized this model to determine the metabolic changes using non-targeted metabolomics analysis of the media. We identified increases in amino acids resulting from muscle atrophy-induced protein degradation (largely sarcomere) that occurs with muscle atrophy that are involved in feeding the Kreb's cycle through anaplerosis. Specifically, we identified increased alanine/proline metabolism (significantly elevated proline, alanine, glutamine, and asparagine) and increased α-ketoglutaric acid, the proposed Kreb's cycle intermediate being fed by the alanine/proline metabolic anaplerotic mechanism. Additionally, several unique pathways not clearly delineated in previous studies of muscle unloading were seen, including: (1) elevated keto-acids derived from branched chain amino acids (i.e. 2-ketoleucine and 2-keovaline), which feed into a metabolic pathway supplying acetyl-CoA and 2-hydroxybutyrate (also significantly increased); and (2) elevated guanine, an intermediate of purine metabolism, was seen at 12h unloading. Given the interest in targeting different aspects of the ubiquitin proteasome system to inhibit protein degradation, this C2C12 system may allow the identification of direct and indirect alterations in metabolism due to anaplerosis or through other yet to be identified mechanisms using a non-targeted metabolomics approach.

Cardiomyocyte-Specific Human Bcl2-Associated Anthanogene 3 P209L Expression Induces Mitochondrial Fragmentation, Bcl2-Associated Anthanogene 3 Haploinsufficiency, and Activates p38 Signaling.

The Bcl2-associated anthanogene (BAG) 3 protein is a member of the BAG family of cochaperones, which supports multiple critical cellular processes, including critical structural roles supporting desmin and interactions with heat shock proteins and ubiquitin ligases intimately involved in protein quality control. The missense mutation P209L in exon 3 results in a primarily cardiac phenotype leading to skeletal muscle and cardiac complications. At least 10 other Bag3 mutations have been reported, nine resulting in a dilated cardiomyopathy for which no specific therapy is available. We generated αMHC-human Bag3 P209L transgenic mice and characterized the progressive cardiac phenotype in vivo to investigate its utility in modeling human disease, understand the underlying molecular mechanisms, and identify potential therapeutic targets. We identified a progressive heart failure by echocardiography and Doppler analysis and the presence of pre-amyloid oligomers at 1 year. Paralleling the pathogenesis of neurodegenerative diseases (eg, Parkinson disease), pre-amyloid oligomers-associated alterations in cardiac mitochondrial dynamics, haploinsufficiency of wild-type BAG3, and activation of p38 signaling were identified. Unexpectedly, increased numbers of activated cardiac fibroblasts were identified in Bag3 P209L Tg+ hearts without increased fibrosis. Together, these findings point to a previously undescribed therapeutic target that may have application to mutation-induced myofibrillar myopathies as well as other common causes of heart failure that commonly harbor misfolded proteins.

BRG1 and BRM SWI/SNF ATPases redundantly maintain cardiomyocyte homeostasis by regulating cardiomyocyte mitophagy and mitochondrial dynamics in vivo.

There has been an increasing recognition that mitochondrial perturbations play a central role in human heart failure. Mitochondrial networks, whose function is to maintain the regulation of mitochondrial biogenesis, autophagy ('mitophagy') and mitochondrial fusion/fission, are new potential therapeutic targets. Yet our understanding of the molecular underpinning of these processes is just emerging. We recently identified a role of the SWI/SNF ATP-dependent chromatin remodeling complexes in the metabolic homeostasis of the adult cardiomyocyte using cardiomyocyte-specific and inducible deletion of the SWI/SNF ATPases BRG1 and BRM in adult mice (Brg1/Brm double mutant mice). To build upon these observations in early altered metabolism, the present study looks at the subsequent alterations in mitochondrial quality control mechanisms in the impaired adult cardiomyocyte. We identified that Brg1/Brm double-mutant mice exhibited increased mitochondrial biogenesis, increases in 'mitophagy', and alterations in mitochondrial fission and fusion that led to small, fragmented mitochondria. Mechanistically, increases in the autophagy and mitophagy-regulated proteins Beclin1 and Bnip3 were identified, paralleling changes seen in human heart failure. Evidence for perturbed cardiac mitochondrial dynamics included decreased mitochondria size, reduced numbers of mitochondria, and an altered expression of genes regulating fusion (Mfn1, Opa1) and fission (Drp1). We also identified cardiac protein amyloid accumulation (aggregated fibrils) during disease progression along with an increase in pre-amyloid oligomers and an upregulated unfolded protein response including increased GRP78, CHOP, and IRE-1 signaling. Together, these findings described a role for BRG1 and BRM in mitochondrial quality control, by regulating mitochondrial number, mitophagy, and mitochondrial dynamics not previously recognized in the adult cardiomyocyte. As critical to the pathogenesis of heart failure, epigenetic mechanisms like SWI/SNF chromatin remodeling seem more intimately linked to cardiac function and mitochondrial quality control mechanisms than previously realized.

Fenofibrate unexpectedly induces cardiac hypertrophy in mice lacking MuRF1.

The muscle-specific ubiquitin ligase muscle ring finger-1 (MuRF1) is critical in regulating both pathological and physiological cardiac hypertrophy in vivo. Previous work from our group has identified MuRF1's ability to inhibit serum response factor and insulin-like growth factor-1 signaling pathways (via targeted inhibition of cJun as underlying mechanisms). More recently, we have identified that MuRF1 inhibits fatty acid metabolism by targeting peroxisome proliferator-activated receptor alpha (PPARα) for nuclear export via mono-ubiquitination. Since MuRF1-/- mice have an estimated fivefold increase in PPARα activity, we sought to determine how challenge with the PPARα agonist fenofibrate, a PPARα ligand, would affect the heart physiologically. In as little as 3 weeks, feeding with fenofibrate/chow (0.05% wt/wt) induced unexpected pathological cardiac hypertrophy not present in age-matched sibling wild-type (MuRF1+/+) mice, identified by echocardiography, cardiomyocyte cross-sectional area, and increased beta-myosin heavy chain, brain natriuretic peptide, and skeletal muscle α-actin mRNA. In addition to pathological hypertrophy, MuRF1-/- mice had an unexpected differential expression in genes associated with the pleiotropic effects of fenofibrate involved in the extracellular matrix, protease inhibition, hemostasis, and the sarcomere. At both 3 and 8 weeks of fenofibrate treatment, the differentially expressed MuRF1-/- genes most commonly had SREBP-1 and E2F1/E2F promoter regions by TRANSFAC analysis (54 and 50 genes, respectively, of the 111 of the genes >4 and <-4 log fold change; P ≤ .0004). These studies identify MuRF1's unexpected regulation of fenofibrate's pleiotropic effects and bridges, for the first time, MuRF1's regulation of PPARα, cardiac hypertrophy, and hemostasis.

Nebulized Delivery of the MAPKAP Kinase 2 Peptide Inhibitor MMI-0100 Protects Against Ischemia-Induced Systolic Dysfunction.

Acute myocardial infarction (AMI) results in systolic dysfunction, myocarditis and fibrotic remodeling, which causes irreversible pathological remodeling of the heart. Associated cell death and inflammation cause cytokine release, which activates the p38 MAPK signaling pathway to propagate damaging signals via MAPKAP kinase 2 (MK2). Previously we showed that intraperitoneal injection of a cell permeable peptide inhibitor of MK2, MMI-0100, protects against fibrosis, apoptosis and systolic dysfunction in a mouse model of AMI induced by left-anterior descending coronary artery (LAD) ligation. Here we tested a new route of administration of MMI-0100: inhalation of nebulized peptide. When given within 30 min of AMI and daily for 2 weeks thereafter, both inhaled and injected MMI-0100 improved cardiac function as measured by conscious echocardiography. Limited fibrosis was observed after 2 weeks by Massons trichrome staining, suggesting that MMI-0100 protects the heart prior to the formation of significant fibrosis. These results support a nebulized route of administration of MMI-0100 can protect the myocardium from ischemic damage.

MuRF2 regulates PPARγ1 activity to protect against diabetic cardiomyopathy and enhance weight gain induced by a high fat diet.

BACKGROUND: In diabetes mellitus the morbidity and mortality of cardiovascular disease is increased and represents an important independent mechanism by which heart disease is exacerbated. The pathogenesis of diabetic cardiomyopathy involves the enhanced activation of PPAR transcription factors, including PPARα, and to a lesser degree PPARß and PPARγ1. How these transcription factors are regulated in the heart is largely unknown. Recent studies have described post-translational ubiquitination of PPARs as ways in which PPAR activity is inhibited in cancer. However, specific mechanisms in the heart have not previously been described. Recent studies have implicated the muscle-specific ubiquitin ligase muscle ring finger-2 (MuRF2) in inhibiting the nuclear transcription factor SRF. Initial studies of MuRF2-/- hearts revealed enhanced PPAR activity, leading to the hypothesis that MuRF2 regulates PPAR activity by post-translational ubiquitination. METHODS: MuRF2-/- mice were challenged with a 26-week 60% fat diet designed to simulate obesity-mediated insulin resistance and diabetic cardiomyopathy. Mice were followed by conscious echocardiography, blood glucose, tissue triglyceride, glycogen levels, immunoblot analysis of intracellular signaling, heart and skeletal muscle morphometrics, and PPARα, PPARß, and PPARγ1-regulated mRNA expression. RESULTS: MuRF2 protein levels increase ~20% during the development of diabetic cardiomyopathy induced by high fat diet. Compared to littermate wildtype hearts, MuRF2-/- hearts exhibit an exaggerated diabetic cardiomyopathy, characterized by an early onset systolic dysfunction, larger left ventricular mass, and higher heart weight. MuRF2-/- hearts had significantly increased PPARα- and PPARγ1-regulated gene expression by RT-qPCR, consistent with MuRF2's regulation of these transcription factors in vivo. Mechanistically, MuRF2 mono-ubiquitinated PPARα and PPARγ1 in vitro, consistent with its non-degradatory role in diabetic cardiomyopathy. However, increasing MuRF2:PPARγ1 (>5:1) beyond physiological levels drove poly-ubiquitin-mediated degradation of PPARγ1 in vitro, indicating large MuRF2 increases may lead to PPAR degradation if found in other disease states. CONCLUSIONS: Mutations in MuRF2 have been described to contribute to the severity of familial hypertrophic cardiomyopathy. The present study suggests that the lack of MuRF2, as found in these patients, can result in an exaggerated diabetic cardiomyopathy. These studies also identify MuRF2 as the first ubiquitin ligase to regulate cardiac PPARα and PPARγ1 activities in vivo via post-translational modification without degradation.