Advanced diagnostic and therapeutic techniques for anaesthetists in thoracic trauma: an evidence-based review.

Anaesthetists play an important role in the evaluation and treatment of patients with signs of thoracic trauma. Anaesthesia involvement can provide valuable input using both advanced diagnostic and therapeutic interventions. Commonly performed interventions may be complicated in this setting including airway management, damage control resuscitation, and acute pain management. Anaesthetists must consider additional factors including airway injuries, vascular injuries, and coagulopathy when treating this population. This evidence-based review discusses traumatic thoracic injuries with a focus on new interventions and modern anaesthesia techniques. This review further serves to support the early involvement of anaesthetists in the emergency department and other areas where they can provide value to the trauma care pathway.

The low molecular weight protein tyrosine phosphatase promotes adipogenesis and subcutaneous adipocyte hypertrophy.

Obesity is a major contributing factor to the pathogenesis of Type 2 diabetes. Multiple human genetics studies suggest that high activity of the low molecular weight protein tyrosine phosphatase (LMPTP) promotes metabolic syndrome in obesity. We reported that LMPTP is a critical promoter of insulin resistance in obesity by regulating liver insulin receptor signaling and that inhibition of LMPTP reverses obesity-associated diabetes in mice. Since LMPTP is expressed in adipose tissue but little is known about its function, here we examined the role of LMPTP in adipocyte biology. Using conditional knockout mice, we found that selective deletion of LMPTP in adipocytes impaired obesity-induced subcutaneous adipocyte hypertrophy. We assessed the role of LMPTP in adipogenesis in vitro, and found that LMPTP deletion or knockdown substantially impaired differentiation of primary preadipocytes and 3T3-L1 cells into adipocytes, respectively. Inhibition of LMPTP in 3T3-L1 preadipocytes also reduced adipogenesis and expression of proadipogenic transcription factors peroxisome proliferator activated receptor gamma (PPARγ) and CCAAT/enhancer-binding protein alpha. Inhibition of LMPTP increased basal phosphorylation of platelet-derived growth factor receptor alpha (PDGFRα) on activation motif residue Y849 in 3T3-L1, resulting in increased activation of the mitogen-associated protein kinases p38 and c-Jun N-terminal kinase and increased PPARγ phosphorylation on inhibitory residue S82. Analysis of the metabolome of differentiating 3T3-L1 cells suggested that LMPTP inhibition decreased cell glucose utilization while enhancing mitochondrial respiration and nucleotide synthesis. In summary, we report a novel role for LMPTP as a key driver of adipocyte differentiation via control of PDGFRα signaling.

PTPN14 phosphatase and YAP promote TGFß signalling in rheumatoid synoviocytes.

OBJECTIVE: We aimed to understand the role of the tyrosine phosphatase PTPN14-which in cancer cells modulates the Hippo pathway by retaining YAP in the cytosol-in fibroblast-like synoviocytes (FLS) from patients with rheumatoid arthritis (RA). METHODS: Gene/protein expression levels were measured by quantitative PCR and/or Western blotting. Gene knockdown in RA FLS was achieved using antisense oligonucleotides. The interaction between PTPN14 and YAP was assessed by immunoprecipitation. The cellular localisation of YAP and SMAD3 was examined via immunofluorescence. SMAD reporter studies were carried out in HEK293T cells. The RA FLS/cartilage coimplantation and passive K/BxN models were used to examine the role of YAP in arthritis. RESULTS: RA FLS displayed overexpression of PTPN14 when compared with FLS from patients with osteoarthritis (OA). PTPN14 knockdown in RA FLS impaired TGFß-dependent expression of MMP13 and potentiation of TNF signalling. In RA FLS, PTPN14 formed a complex with YAP. Expression of PTPN14 or nuclear YAP-but not of a non-YAP-interacting PTPN14 mutant-enhanced SMAD reporter activity. YAP promoted TGFß-dependent SMAD3 nuclear localisation in RA FLS. Differences in epigenetic marks within Hippo pathway genes, including YAP, were found between RA FLS and OA FLS. Inhibition of YAP reduced RA FLS pathogenic behaviour and ameliorated arthritis severity. CONCLUSION: In RA FLS, PTPN14 and YAP promote nuclear localisation of SMAD3. YAP enhances a range of RA FLS pathogenic behaviours which, together with epigenetic evidence, points to the Hippo pathway as an important regulator of RA FLS behaviour.

Diabetes reversal by inhibition of the low-molecular-weight tyrosine phosphatase.

Obesity-associated insulin resistance plays a central role in type 2 diabetes. As such, tyrosine phosphatases that dephosphorylate the insulin receptor (IR) are potential therapeutic targets. The low-molecular-weight protein tyrosine phosphatase (LMPTP) is a proposed IR phosphatase, yet its role in insulin signaling in vivo has not been defined. Here we show that global and liver-specific LMPTP deletion protects mice from high-fat diet-induced diabetes without affecting body weight. To examine the role of the catalytic activity of LMPTP, we developed a small-molecule inhibitor with a novel uncompetitive mechanism, a unique binding site at the opening of the catalytic pocket, and an exquisite selectivity over other phosphatases. This inhibitor is orally bioavailable, and it increases liver IR phosphorylation in vivo and reverses high-fat diet-induced diabetes. Our findings suggest that LMPTP is a key promoter of insulin resistance and that LMPTP inhibitors would be beneficial for treating type 2 diabetes.

The Combination of IV and Perineural Dexamethasone Prolongs the Analgesic Duration of Intercostal Nerve Blocks Compared with IV Dexamethasone Alone.

Objective: The use of multiple-level, single-injection intercostal nerve blocks for pain control following video-assisted thorascopic surgery (VATS) is limited by the analgesic duration of local anesthetics. This study examines whether the combination of perineural and intravenous (IV) dexamethasone will prolong the duration of intraoperatively placed intercostal nerve blocks following VATS compared with IV dexamethasone and a perineural saline placebo. Design: Prospective, double-blind, randomized placebo-controlled trial. Setting: Single level-1 academic trauma center. Subjects: Forty patients undergoing a unilateral VATS under the care of a single surgeon. Methods: Patients were randomly assigned to two groups and received an intercostal nerve block containing 1) 0.5% bupivacaine with epinephrine and 1 ml of 0.9% saline or 2) 0.5% bupivacaine with epinephrine and 1 ml of a 4 mg/ml dexamethasone solution. All patients received 8 mg of IV dexamethasone. Results: Group 2 had lower NRS-11 scores at post-operative hours 8 (5.05, SD = 2.13 vs 3.50, SD = 2.50; p = 0.04), 20 (4.30, SD = 2.96 vs 2.26, SD = 2.31; p = 0.02), and 24 (4.53, SD = 1.95 vs 2.26, SD = 2.31; p = 0.02). Equianalgesic opioid requirement was decreased in group 2 at 32 hours (5.78 mg, SD = 5.77 vs 1.67 mg, SD = 3.49; p = 0.02). Group 2 also had greater FEV1 measured at 8, 12, 24, and 44 hours; greater FVC at 24 hours; greater PEF at 28 through 48 hours; and greater FEV1/FVC at 8 and 36 hours. Conclusions: The combination of IV and perineural dexamethasone prolonged the duration of a single-injection bupivacaine intercostal nerve block as measured by NRS-11 compared with IV dexamethasone alone at 24 hours. Reduced NRS-11 at other times, reduced opioid requirements, and increased PFTs were observed in group 2.

Erythroferrone exacerbates iron overload and ineffective extramedullary erythropoiesis in a mouse model of ß-thalassemia.

ß-thalassemia is characterized by chronic hepcidin suppression and iron overload, even in patients who have not undergone transfusion. The HbbTh3/+ (Th3/+) mouse model of nontransfusion-dependent ß-thalassemia (NTDBT) partially recapitulates the human phenotype but lacks chronic hepcidin suppression, progressive iron accumulation into adulthood, or the interindividual variation of the rate of iron loading observed in patients. Erythroferrone (ERFE) is an erythroid regulator that suppresses hepcidin during increased erythropoiesis. ERFE concentrations in the sera of patients with NTDBT correlate negatively with hepcidin levels but vary over a broad range, possibly explaining the variability of iron overload in patients. To analyze the effect of high ERFE concentrations on hepcidin and iron overload in NTDBT, we crossed Th3/+ mice with erythroid ERFE-overexpressing transgenic mice. Th3/ERFE-transgenic mice suffered high perinatal mortality, but embryos at E18.5 showed similar viability, appearance, and anemia effects as Th3/+ mice. Compared with Th3/+ littermates, adult Th3/ERFE mice had similarly severe anemia but manifested greater suppression of serum hepcidin and increased iron accumulation in the liver, kidney, and spleen. The Th3/ERFE mice had much higher concentrations of serum ERFE than either parental strain, a finding attributable to both a higher number of erythroblasts and higher production of ERFE by each erythroblast.Th3/+ and Th3/ERFE mice had similar red blood cell count and shortened erythrocyte lifespan, but Th3/ERFE mice had an increased number of erythroid precursors in their larger spleens, indicative of aggravated ineffective extramedullary erythropoiesis. Thus, high ERFE concentrations increase the severity of nontransfusional iron overload and ineffective erythropoiesis in thalassemic mice but do not substantially affect anemia or hemolysis.

A mouse model characterizes the roles of ZIP8 in systemic iron recycling and lung inflammation and infection.

ZIP8 (SLC39A8) is a transmembrane divalent metal ion importer that is most highly expressed in the lung and is inducible by inflammatory stimuli. In addition to zinc and manganese, ZIP8 can transport iron, but its specific roles in iron regulation during homeostatic and pathologic processes remain poorly understood. Using a novel global inducible ZIP8 knockout (KO) mouse, we analyzed the role of ZIP8 in steady-state iron homeostasis and during inflammation and infection. We observed an unexpected phenotype of elevated spleen iron levels and decreased serum iron in ZIP8 KO mice, suggesting that ZIP8 plays a role in iron recycling. We also showed that ZIP8 is expressed on lung distal airspace epithelial cells and transports iron from the airway into lung tissue. LPS-induced inflammation induced ZIP8 expression in the lung, but ZIP8 deletion had no detrimental effect on the severity of LPS-induced acute lung injury or on the outcomes of Klebsiella pneumoniae lung infection. Thus, ZIP8 plays a role in systemic iron homeostasis but does not modulate the severity of inflammatory lung injury or the host defense against a common bacterial cause of pneumonia.

Bmpr2 mutant mice are an inadequate model for studying iron deficiency in pulmonary hypertension.

As bone morphogenetic protein receptor type II (Bmpr2) mutations are the most common genetic cause of pulmonary arterial hypertension (PAH), and iron deficiency (ID) is associated with worse clinical outcomes in PAH patients, we proposed to use Bmpr2 ± mice to induce a model of ID in pulmonary vascular disease. Our study shows that these transgenic mice are not a good model for this clinical phenomenon.

Iron overload causes a mild and transient increase in acute lung injury.

Recent studies have demonstrated a strong link between acute respiratory distress syndrome (ARDS) and the levels of iron and iron-related proteins in the lungs. However, the role of iron overload in ARDS development has yet to be characterized. In this study, we compared the highly iron-overloaded hepcidin knockout mice (HKO) to their iron-sufficient wild-type (WT) littermates in a model of sterile acute lung injury (ALI) induced by treatment with oropharyngeal (OP) LPS. There were no major differences in systemic inflammatory response or airway neutrophil infiltration between the two groups at the time of maximal injury (days 2 and 3) or during the recovery phase (day 7). Hepcidin knockout mice had transiently increased bronchoalveolar lavage fluid (BALF) protein and MPO activity in the lung and BALF on day 3, indicating worse vascular leakage and increased neutrophil activity, respectively. The increased ALI severity in iron-overloaded mice may be a result of increased apoptosis of lung tissue, as evidenced by an increase in cleaved capsase-3 protein in lung homogenates from HKO mice versus WT mice on day 3. Altogether, our data suggest that even severe iron overload has a relatively minor and transient effect in LPS-induced ALI.

Iron in Lung Pathology.

The lung presents a unique challenge for iron homeostasis. The entire airway is in direct contact with the environment and its iron particulate matter and iron-utilizing microbes. However, the homeostatic and adaptive mechanisms of pulmonary iron regulation are poorly understood. This review provides an overview of systemic and local lung iron regulation, as well as the roles of iron in the development of lung infections, airway disease, and lung injury. These mechanisms provide an important foundation for the ongoing development of therapeutic applications.

Abnormal PTPN11 enhancer methylation promotes rheumatoid arthritis fibroblast-like synoviocyte aggressiveness and joint inflammation.

The PTPN11 gene, encoding the tyrosine phosphatase SHP-2, is overexpressed in rheumatoid arthritis (RA) fibroblast-like synoviocytes (FLS) compared with osteoarthritis (OA) FLS and promotes RA FLS invasiveness. Here, we explored the molecular basis for PTPN11 overexpression in RA FLS and the role of SHP-2 in RA pathogenesis. Using computational methods, we identified a putative enhancer in PTPN11 intron 1, which contained a glucocorticoid receptor- binding (GR-binding) motif. This region displayed enhancer function in RA FLS and contained 2 hypermethylation sites in RA compared with OA FLS. RA FLS stimulation with the glucocorticoid dexamethasone induced GR binding to the enhancer and PTPN11 expression. Glucocorticoid responsiveness of PTPN11 was significantly higher in RA FLS than OA FLS and required the differentially methylated CpGs for full enhancer function. SHP-2 expression was enriched in the RA synovial lining, and heterozygous Ptpn11 deletion in radioresistant or innate immune cells attenuated K/BxN serum transfer arthritis in mice. Treatment with SHP-2 inhibitor 11a-1 reduced RA FLS migration and responsiveness to TNF and IL-1ß stimulation and reduced arthritis severity in mice. Our findings demonstrate how abnormal epigenetic regulation of a pathogenic gene determines FLS behavior and demonstrate that targeting SHP-2 or the SHP-2 pathway could be a therapeutic strategy for RA.