Faculty Bibliography

Cytokinins are adenine-based hormones that have been well-characterized in plants but are also made by bacteria, including the human-exclusive pathogen Mycobacterium tuberculosis. Like plants, M. tuberculosis uses cytokinins to regulate gene expression. We previously established that cytokinin overaccumulation in M. tuberculosis results in a buildup of aldehydes produced during cytokinin breakdown. In plants, dedicated enzymes called cytokinin oxidases convert cytokinins into adenine and various aldehydes. Proteasome degradation-deficient M. tuberculosis, which cannot degrade the cytokinin-producing enzyme Log, accumulates several cytokinins and at least one cytokinin-associated aldehyde, resulting in increased sensitivity to nitric oxide and copper. We therefore hypothesized that M. tuberculosis encodes one or more cytokinin oxidases, and disruption of this enzyme might restore resistance to nitric oxide and copper in a proteasome-defective strain. Using a homology-based search, we identified Rv3719 as a protein with high similarity to a plant cytokinin oxidase. Deletion of this gene, however, did not restore nitric oxide or copper resistance to a degradation-defective mutant. Instead, we observed increased copper sensitivity when Rv3719 was deleted from either wild-type or proteasome-defective strains. Finally, we characterized Rv3718c, a protein encoded adjacent to Rv3719, and found that it bound a cytokinin with high specificity. Collectively, these data support a role for cytokinin activity in M. tuberculosis physiology that remains to be further elucidated.IMPORTANCENumerous bacterial species encode cytokinin-producing enzymes, the functions of which are almost completely unknown. This work contributes new knowledge to the cytokinin field for bacteria and reveals further conservation of cytokinin-associated proteins between plants and prokaryotes.

OBJECTIVE:The purpose of this study was to determine the association of hypoalbuminemia with adverse outcomes in patients undergoing surgical repair of nonunions or malunions of upper and lower extremity long bones. METHODS:DESIGN: Retrospective. SETTING/METHODS:Hospitals participating in American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) from 2005 to 2019. PATIENTS/METHODS:Patients in the ACS-NSQIP database with upper extremity and lower extremity fractures who underwent nonunion or malunion repairs and had preoperative serum albumin levels. Outcome Measures and Comparisons: Demographic variables, comorbidities and postoperative complications were collected and compared using t tests and chi squared tests. Multivariate linear regression models were used to assess complications, adjusting for variables such as age, sex, BMI, hospital length of stay, and operation time. RESULTS:Univariate analysis of 1640 total patients (338 [20.6%] with hypoalbuminemia and 1302 [79.4%] with normal albumin) showed patients with hypoalbuminemia had significantly increased 30-day mortality rates, increased lengths of stay, and returns to the operating room. Multivariate analysis showed patients with hypoalbuminemia had significantly greater odds for any complication (OR: 2.62; 95% CI [1.77, 3.84]; p < 0.001), surgical site infections (OR: 2.62; 95% CI [1.34, 4.99]; p = 0.004) and transfusions (OR: 2.77; 95% CI: [1.62, 4.69]; p < 0.001) compared to the normal albumin group. CONCLUSIONS:There was a significant difference in 30-day postoperative complications between patients with normal albumin levels and those who were hypoalbuminemic after surgical repairs of nonunions or malunions. Albumin level is a risk factor that should be monitored and counseled upon prior to surgical intervention for nonunion or malunion correction. LEVEL OF EVIDENCE/METHODS:Level III Retrospective Comparative Study.

The capacity of the brain to compensate for insults during development depends on the type of cell loss, whereas the consequences of genetic mutations in the same neurons are difficult to predict. We reveal powerful compensation from outside the mouse cerebellum when the excitatory cerebellar output neurons are ablated embryonically and demonstrate that the main requirement for these neurons is for motor coordination and not basic learning and social behaviors. In contrast, loss of the homeobox transcription factors Engrailed1/2 (EN1/2) in the cerebellar excitatory lineage leads to additional deficits in adult learning and spatial working memory, despite half of the excitatory output neurons being intact. Diffusion MRI indicates increased thalamo-cortico-striatal connectivity in En1/2 mutants, showing that the remaining excitatory neurons lacking En1/2 exert adverse effects on extracerebellar circuits regulating motor learning and select non-motor behaviors. Thus, an absence of cerebellar output neurons is less disruptive than having cerebellar genetic mutations.

Modulating mechanotransduction by inhibiting yes-associated protein (YAP) in mice yields wound regeneration without scarring. However, rodents are loose-skinned and fail to recapitulate key aspects of human wound repair. We sought to elucidate the effects of YAP inhibition in red Duroc pig wounds, the most human-like model of scarring. We show that one-time treatment with verteporfin, a YAP inhibitor, immediately after wounding is sufficient to prevent scarring and to drive wound regeneration in pigs. By performing single-cell RNA sequencing (scRNA-seq) on porcine wounds in conjunction with spatial proteomic analysis, we found perturbations in fibroblast dynamics with verteporfin treatment and the presence of putative pro-regenerative/profibrotic fibroblasts enriched in regenerating/scarring pig wounds, respectively. We also identified differences in enriched myeloid cell subpopulations after treatment and linked this observation to increased elaboration of interleukin-33 (IL-33) in regenerating wounds. Finally, we validated our findings in a xenograft wound model containing human neonatal foreskin engrafted onto nude mice and used scRNA-seq of human wound cells to draw parallels with fibroblast subpopulation dynamics in porcine wounds. Collectively, our findings provide support for the clinical translation of local mechanotransduction inhibitors to prevent human skin scarring, and they clarify a YAP/IL-33 signaling axis in large animal wound regeneration.

The ε4 variant of human apolipoprotein E (APOE4) is a key genetic risk factor for neurodegeneration in Alzheimer's disease and elevated all-cause mortality in humans. Understanding the factors and mechanisms that can mitigate the harmful effects of APOE4 has significant implications. In this study, we find that inactivating the VHL-1 (Von Hippel-Lindau) protein can suppress mortality, neural and behavioral pathologies caused by transgenic human APOE4 in Caenorhabditis elegans. The protective effects of VHL-1 deletion are recapitulated by stabilized HIF-1 (hypoxia-inducible factor), a transcription factor degraded by VHL-1. HIF-1 activates a genetic program that safeguards against mitochondrial dysfunction, oxidative stress, proteostasis imbalance, and endolysosomal rupture-critical cellular events linked to neural pathologies and mortality. Furthermore, genetic inhibition of Vhl reduces cerebral vascular injury and synaptic lesions in APOE4 mice, suggesting an evolutionarily conserved mechanism. Thus, we identify the VHL-HIF axis as a potent modulator of APOE4-induced neural pathologies and propose that targeting this pathway in nonproliferative tissues may curb cellular damage, protect against neurodegeneration, and reduce tissue injuries and mortality.

INTRODUCTION/BACKGROUND:In city hospitals, subway-related traumatic amputations are a frequent pattern of injury, however there is a paucity of literature on this specific injury pattern. The purpose of this study was to describe the epidemiology of subway-related traumatic amputations, as well as compare them to non-subway traumatic amputations. PATIENTS AND METHODS/METHODS:Retrospective review was performed at a single Level-1 trauma center in a metropolitan area. All patients who sustained a traumatic lower-extremity amputation over a seven-year period were included. Demographics, injury, treatment-related information, and complications were collected. Subway and non-subway traumatic amputations were statistically compared. Cohorts were further subdivided into above-knee amputations (AKAs) and below-knee amputations (BKAs) for statistical comparison. RESULTS:Fifty-seven patients sustained 72 traumatic lower-extremity amputations, including 64 subway-related amputations. Fifteen patients with bilateral lower-extremity amputations all had subway-related injuries. Patients with subway-related injuries were more likely to have a history of alcohol use disorder (58.1 % vs. 0 %; P = 0.002), and experienced longer stays in the intensive care unit (ICU) (8.9 vs. 3.6 days; P = 0.006). Twenty-four amputations (33.3 %) were complicated by wound infection during the initial hospitalization, with wound cultures growing a variety of organisms, most frequently Enterococcus species and Enterobacter cloacae. When subway injuries were separated by AKAs and BKAs, patients with AKAs underwent more irrigation and debridement procedures on average (10.3 vs. 5.8; P = 0.006), had a higher rate of wound infections (58.8 % vs. 25.0 %; P = 0.018), and had longer hospital stays (50.4 vs. 32.2 days; P = 0.047). CONCLUSION/CONCLUSIONS:Subway-related amputations are associated with longer ICU stays and a history of alcohol use disorder compared to non-subway traumatic amputations. Approximately 1/3 of these patients are expected to develop a wound infection, with Enterococcus and Enterobacter species being the most commonly identified organisms. Further research into high-energy, traumatic amputations, including subway injuries, may help improve prognostication of patient outcomes, identify potential in-hospital complications, and proactively direct differences in care compared to the standard for non-subway-related amputations. LEVEL OF EVIDENCE/METHODS:Prognostic Level III.

It has been well established that adenosine plays a key role in the control of inflammation through G protein coupled receptors and recently shown that it can regulate thermogenesis. Here we investigated the specific requirements of the adenosine A2A receptor (A2AR) in mature adipocytes for thermogenic functionality and metabolic homeostasis. We generated fat tissue-specific adenosine A2AR KO mice to assess the influence of signaling through this receptor on brown and beige fat functionality, obesity, insulin sensitivity, inflammation, and liver function. Fat-specific A2AR KO and WT littermate mice were compared for potential differences in cold tolerance and energy metabolism. In addition, we measured glucose metabolism, AT inflammation, and liver phenotypes in mice of the two genotypes after exposure to a diet rich in fat. Our results provide novel evidence indicating that loss of the adenosine A2AR specifically in adipocytes is associated with cold intolerance and decreased oxygen consumption. Furthermore, mice with fat specific ablation of the A2AR exposed to a diet rich in fat showed increased propensity to obesity, decreased insulin sensitivity, elevated adipose tissue inflammation, and hepato-steatosis and hepato-steatitis. Overall, our data provide novel evidence that A2AR in mature adipocytes safeguards metabolic homeostasis, suggesting the possibility of targeting this receptor selectively in fat for the treatment of metabolic disease.

OBJECTIVE:Genome-wide association studies implicate metabo-psychiatric origins for anorexia nervosa (AN). There are two case reports totaling six adult females who experienced complete remission of AN following a treatment comprised of ketogenic diet (targeting metabolism) with ketamine infusions (targeting psychiatric origins), but no study has determined the efficacy of ketogenic diet, alone. We addressed this gap in knowledge, with exploration of potential molecular mechanisms, using an animal model. METHOD/METHODS:Adult C57BL6 female mice underwent 2 or 3 cycles of activity-based anorexia (ABA1, ABA2, ABA3), an animal model of AN relapse, in which AN-like maladaptive behaviors of hyperactivity and voluntary food restriction are elicited when wheel access is combined with food restriction. ABA was categorized as severe, based on weight loss ≥ 20%, food restriction-evoked increase in wheel counts > 10,000/6 h, and crouching/grimace, and compared across two groups: (1) KG, fed ketogenic food continuously (N = 25); and (2) CON, fed standard diet (N = 28). RESULTS:86% of CON versus none of the KG were crouching with grimace during ABA1. 93% of CON versus 11% of KG lost weight severely during ABA2 (p < 0.001, 8% difference of group mean weights). Severe hyperactivity was prevalent among CON (86%) and rare for KG (4%) during ABA2 (p < 0.001 on all food-restricted days). ABA up-regulated BDNF (brain-derived neurotrophic factor) in the hippocampus of both groups but ketone body, β-hydroxybutyrate, in urine was increased only among KG. DISCUSSION/CONCLUSIONS:Ketogenic diet may reduce severity of AN relapse through reduction of compulsive exercise, via mechanisms that are in addition to BDNF up-regulation and involve β-hydroxybutyrate.

BACKGROUND/UNASSIGNED:Endovascular abdominal aortic aneurysm repair (EVAR) is a preferred surgery to prevent aneurysm sac enlargement and minimize the risk of life-threatening rupture in patients with AAA. Serious complications of type II endoleaks following EVAR can cause sac expansion and increase rupture risk. This study focused on evaluating clinical and blood characteristics in patients with type II endoleaks to refine our understanding of systemic fluctuations associated with unsuccessful EVAR. METHODS/UNASSIGNED:This retrospective study included 146 patients with AAA who underwent primary elective endovascular procedures (EVAR/fEVAR) between 2013 and 2021. Clinical characteristics, complete blood count (CBC) and imaging data were analyzed from patients who did and did not develop type II endoleaks. RESULTS/UNASSIGNED:Mean platelet volume (MPV) was significantly increased in patients who developed type II endoleaks after EVAR. Receiver operating characteristic analysis showed that MPV has a satisfactory discriminatory performance in distinguishing post-EVAR patients who developed type II endoleaks, yielding an area under the curve (AUC) value of 0.64. A risk stratification panel incorporating MPV, type II diabetes history, and administration of dual antiplatelet therapies yielded an AUC of 0.70 and predicted an endoleak-free survival rate with a hazard ratio of 2.94. A nomogram revealed that MPV had the highest scoring weight among all significant variables. CONCLUSION/UNASSIGNED:Patients with type II endoleaks following EVAR have elevated MPV indicative of different phenotypes of circulating platelets. MPV presents an attractive predictive criteria for assessing the occurrence of type II endoleaks in patients with AAA.

BACKGROUND/UNASSIGNED:Cholesterol efflux capacity (CEC) of HDL (high-density lipoprotein) is inversely associated with incident cardiovascular events, independent of HDL cholesterol. Obesity is characterized by low HDL cholesterol and impaired HDL function, such as CEC. Bariatric surgery, including Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG), broadly leads to improved cardiovascular outcomes, but impacts on risk factors differ by procedure, with greater improvements in weight loss, blood pressure, and glycemic control after RYGB, but greater improvements in HDL cholesterol and CEC levels after SG. This study sought to determine effects of RYGB and SG on HDL protein and lipid cargo and investigate associations with CEC changes. METHODS/UNASSIGNED:We prospectively studied nondiabetic, premenopausal Hispanic women with severe obesity not using lipid medications undergoing RYGB (n=31) or SG (n=36). Anthropometric measurements and blood sampling were obtained before and at 6 and 12 months after surgery. HDL was isolated from plasma, and quantitative proteomic and lipidomic assessments were performed with LC-MS/MS (liquid chromatography with tandem mass spectrometry). CEC was assessed ex vivo using apoB-depleted serum. RESULTS/UNASSIGNED:Participants experienced similar, significant weight loss over 12 months following bariatric surgery (38.0±10.4 kg) regardless of the procedure. Relative quantities of 47 proteins (34 increased, 13 decreased) and 150 lipids (71 increased, 79 decreased) carried on HDL were significantly altered following either surgical procedure. Proteins with similar aggregate response patterns were clustered into 15 groups (5 increased, 5 decreased, 5 minimal change) and lipids with similar aggregate responses into 25 groups (7 increased, 11 decreased, 7 minimal change). Network mediation analyses suggested that changes in 4 protein and 2 lipid clusters mediated changes in ABCA1 (ATP-binding cassette transporter A1) CEC and that 1 lipid cluster mediated changes in non-ABCA1 CEC. The protein and lipid clusters that mediated changes in CEC were distinct between SG and RYGB. CONCLUSIONS/UNASSIGNED:Bariatric surgery produces substantial changes in HDL lipid and protein cargo, and specific changes may mediate changes in HDL function in CEC. Further study of these mechanisms may lead to improved interventions to reduce cardiovascular risk in patients with obesity.