Dual phenotypic characteristics of P-selectin in a mouse model of hemorrhagic shock and hepatectomy.

Background: Membrane-bound P-selectin induces endothelial adhesion of leucocytes and amplifies organ inflammations during major trauma, while soluble P-selectin (sP-sel) mediates survival rescue properties. This study characterized the differential effects of P-selectin in a "2-hit" model of hemorrhagic shock (HS) and partial hepatectomy (PH). Materials and methods: HS was induced by withdrawing blood (0.3 mL) directly from the mouse femoral arteries. 70% or 50% of liver volumes were resected after inducing HS. Time of survival in P-selectin deficient (Selp -/-) mice treated with and without intraperitoneal injections of recombinant P-sel IgG-Fc fusion proteins (rP-sel-Fc, 1.5 mg/kg) were recorded for up to 72h after injury. In addition, liver regeneration at 72h after HS and 50% PH was assessed in wild-type and Selp -/- mice. Results: Compared to wild-types, Selp -/- mice had significantly higher mortality rates post HS and 70% PH, as none of these animals survived up to 48h postoperatively. The survival curve was restored in Selp -/- mice pre-treated with rP-sel-Fc. In the HS followed by 50% PH experimental arm, liver remnant growth ratios were significantly higher in Selp -/- mice (15.7 ± 3.1 vs 11.7 ± 4.9, P = 0.040). The elevated serum concentrations of alanine aminotransferase post-PH were significantly reduced in Selp -/- mice. Hepatocyte proliferation indices (CYP7a1 and PCNA) expression were enhanced and myeloperoxidase activity in the regenerated remnant liver was reduced in the Selp -/- mice. Conclusion: In critical conditions induced by HS and PH, P-selectin mediates two distinct phenotypic characteristics. Soluble-form circulating P-selectin improves survival in the acute stage of HS and extensive loss of liver parenchyma; membrane-bound P-selectin induces regional pro-inflammatory reactions in the remnant liver after the acute stage of two insults, thereby inhibiting hepatic regeneration. The results of this pre-clinical study may provide molecular mechanistic insight and clinical therapeutic applications of P-selectin in the acute and regenerative phases of traumatic hepatic injury.

Viable Allogeneic Mitochondria Transplantation Improves Gas Exchange and Alveolar-Capillary Permeability in Rats with Endotoxin-Induced Acute Lung Injuries.

Background: Acute lung injuries (ALI) cause disruption of the alveolar-capillary barrier and is the leading cause of death in critically ill patients. This study tested the hypothesis that the administration of freshly isolated viable allogeneic mitochondria can prevent alveolar-capillary barrier injuries at the endothelial level, as mitochondrial dysfunction of the pulmonary endothelium is a critical aspect of ALI progression. Methods: ALI was induced by intratracheal lipopolysaccharide instillation (LPS, 1mg/kg) in anesthetized rats. Mitochondria (100 µg) were isolated from the freshly harvested soleus muscles of naïve rats and stained with a green fluorescence MitoTracker™ dyne. A mitochondria or placebo solution was randomly administered into the jugular veins of the rats at 2 h and 4 h after ALI induction. An arterial blood gas analysis was done 20 h later. The animals were then sacrificed and lung tissues were harvested for analysis. Results: An IVIS Spectrum imaging system was used to obtain ex vivo heart-lung block images and track the enhancement of MitoTracker™ fluorescence in the lungs. Mitochondria transplantation significantly improved arterial oxygen contents (PaO2 and SaO2) and reduced CO2 tension in rats with ALI. Animals with mitochondrial transplants had significantly higher ATP concentrations in their lung tissues. Allogeneic mitochondria transplantation preserved alveolar-capillary barrier function, as shown by a reduction in protein levels in the bronchoalveolar lavage fluid and decreased extravasated Evans blue dyne and hemoglobin content in lung tissues. In addition, relaxation responses to acetylcholine and eNOS expression were potentiated in injured pulmonary arteries and inflammatory cells infiltration into lung tissue was reduced following mitochondrial transplantation. Conclusions: Transplantation of viable mitochondria protects the integrity of endothelial lining of the alveolar-capillary barrier, thereby improving gas exchange during the acute stages of endotoxin-induced ALI. However, the long-term effects of mitochondrial transplantation on pulmonary function recovery after ALI requires further investigation.

Transplantation of viable mitochondria improves right ventricular performance and pulmonary artery remodeling in rats with pulmonary arterial hypertension.

OBJECTIVE: Because mitochondrial dysfunction is a key factor in the progression of pulmonary hypertension, this study tested the hypothesis that transplantation of exogenous viable mitochondria can reverse pulmonary artery remodeling and restore right ventricular performance in pulmonary hypertension. METHODS: Pulmonary hypertension was induced by parenteral injection of monocrotaline (60 mg/kg) and creation of a left-to-right shunt aortocaval fistula in rats. Three weeks after creation of fistula, the animals were randomly assigned to receive intravenous delivery of placebo solution or allogeneic mitochondria once weekly for 3 consecutive weeks. Mitochondria (100 µg) were isolated from the freshly harvested soleus muscles of naïve rats. Transthoracic echocardiography was performed at 3 weeks after mitochondrial delivery. RESULTS: Ex vivo heart-lung block images acquired by an IVIS Spectrum (PerkinElmer, Waltham, Mass) imaging system confirmed the enhancement of MitoTracker (Invitrogen, Carlsbad, Calif) fluorescence in the pulmonary arteries. Mitochondria transplantation significantly increased lung tissue adenosine triphosphate concentrations and improved right ventricular performance, as evidenced by a reduction in serum levels of B-type natriuretic peptide and ventricular diameter. Right ventricular mass and wall thickness were restored in the mitochondrial group. In the pulmonary arteries of rats that received mitochondrial treatment, vascular smooth muscle cells expressed higher levels of α-smooth muscle actin and smooth muscle myosin heavy chain II, indicating the maintenance of the nonproliferative, contractile phenotype. The hyper-reactivity of isolated pulmonary arteries to α-adrenergic stimulation was also attenuated after mitochondrial transplantation. CONCLUSIONS: Transplantation of viable mitochondria can restore the contractile phenotype and vasoreactivity of the pulmonary artery, thereby reducing the afterload and right ventricular remodeling in rats with established pulmonary hypertension. The improvement in overall right ventricular performance suggests that mitochondrial transplantation can be a revolutionary clinical therapeutic option for the management of pulmonary hypertension.

Prolonged preoperative fasting induces postoperative insulin resistance by ER-stress mediated Glut4 down-regulation in skeletal muscles.

Preoperative fasting aims to prevent pulmonary aspiration and improve bowel preparation, but it may induce profound systemic catabolic responses that lead to protein breakdown and insulin-resistant hyperglycemia after operation. However, the molecular mechanisms of catabolic reaction induced by prolonged preoperative fasting and surgical stress are undetermined. In this study, anesthetized rats were randomly assigned to receive a sham operation or laparotomy cecectomy. Fasting groups were restricted from food and water for 12 h before operation, while the feeding group had free access to food throughout the study period. Twenty-four hours after operation, the animals were sacrificed to collect blood samples and soleus muscles for analysis. Postoperative blood glucose level was significantly increased in the fasting group with elevated serum insulin and C-peptide. Continuous feeding reduced serum myoglobin and lactate dehydrogenase concentrations. Preoperative fasting activated inositol-requiring transmembrane kinase/endoribonuclease (IRE)-1α and c-Jun N-terminal kinase (JNK) mediated endoplasmic reticulum (ER)-stress, and reduced glucose transporter type 4 (Glut4) expression in the soleus muscle. Phospholamban phosphorylation was reduced and intracellular calcium levels were increased in the isolated skeletal muscle cells. Similar results were found in ER stress-induced C1C12 myoblasts. The expression of Glut4 was suppressed in the stressed C1C12, but was potentiated following inhibition of ER stress and chelation of intracellular free calcium. This study provides evidence demonstrating that prolonged preoperative fasting induces ER stress and generates insulin resistance in the skeletal muscle through suppression of Glut4 and inactivation of Ca2+-ATPase, leading to intracellular calcium homeostasis disruption and peripheral insulin resistance.

Exendin-4, a glucagon-like peptide-1 analogue accelerates healing of chronic gastric ulcer in diabetic rats.

BACKGROUND: Diabetes mellitus is an independent risk factor for impaired healing of peptic ulcers, and there are currently no supplementary therapeutics other than the standard antipeptic medicine to improve the ulcer healing in diabetes. This study examined the potential pleiotropic effect of a glucagon-like peptide (Glp)-1 analogue exendin (Ex)-4 on the regeneration of gastric ulcer in streptozotocin-induced diabetic rats. METHODS AND RESULTS: Chronic ulcer was created in rat stomach by submucosal injection of acetic acid and peri-ulcer tissues were analyzed 7 days after operation. Ulcer wound healing was impaired in diabetic rats with suppressed tissue expression of eNOS and enhanced levels of pro-inflammatory reactions. Treatment with intraperitoneal injection of Ex4 (0.5 µg/kg/d) significantly reduced the area of gastric ulcer without changing blood glucose level. Ex-4 restored the expression of pro-angiogenic factors, and attenuated the generation of regional inflammation and superoxide anions. The improvement of ulcer healing was associated with increased expression of MMP-2 and formation of granulation tissue in the peri-ulcer area. CONCLUSION: Administration of Ex4 may induce pro-angiogenic, anti-inflammatory and anti-oxidative reactions in the peri-ulcer tissue of diabetic rats that eventually enhances tissue granulation and closure of ulcerative wounds. Our results support the potential clinical application of Glp-1 analogues as supplementary hypoglycemic agents in the antipeptic ulcer medication in diabetes.