Remodeling of the Residual Gastric Mucosa after Roux-En-Y Gastric Bypass or Vertical Sleeve Gastrectomy in Diet-Induced Obese Rats

Whereas the remodeling of intestinal mucosa after bariatric surgeries has been the matter of numerous studies to our knowledge, very few reported on the remodeling of the residual gastric mucosa. In this study, we analyzed remodeling of gastric mucosa after Roux-en-Y gastric bypass (RYGB) and vertical sleeve gastrectomy (VSG) in rats. Diet-induced obese rats were subjected to RYGB, VSG or sham surgical procedures. All animals were assessed for food intake, body-weight, fasting blood, metabolites and hormones profiling, as well as insulin and glucose tolerance tests before and up to 5 weeks post-surgery. Remodeling of gastric tissues was analyzed by routine histology and immunohistochemistry studies, and qRT-PCR analyses of ghrelin and gastrin mRNA levels. In obese rats with impaired glucose tolerance, VSG and RYGB caused substantial weight loss and rats greatly improved their oral glucose tolerance. The remaining gastric mucosa after VSG and gastric pouch (GP) after RYGB revealed a hyperplasia of the mucous neck cells that displayed a strong immunoreactivity for parietal cell H⁺/K⁺-ATPase. Ghrelin mRNA levels were reduced by 2-fold in remaining fundic mucosa after VSG and 10-fold in GP after RYGB. In the antrum, gastrin mRNA levels were reduced after VSG in line with the reduced number of gastrin positive cells. This study reports novel and important observations dealing with the remaining gastric mucosa after RYGB and VSG. The data demonstrate, for the first time, a hyperplasia of the mucous neck cells, a transit cell population of the stomach bearing differentiating capacities into zymogenic and peptic cells.     

Synthesis of a New Tri-Branched PEG-IFNα2 and Its Impact on Anti Viral Bioactivity

Efficacy of proteins can be enhanced by using polyethylene glycol (PEG) conjugation (PEGylation) to the protein molecules. Mobile non-toxic PEG chains conjugated to bio-therapeutics increase their hydrodynamic volume and in turn can prolong their plasma retention time and increase their solubility. An important aspect of PEGylation is the selection of PEG molecule with suitable structure and molecular weight. In this study, conceiving the idea that branched PEG-conjugates show superior efficacy over the linear PEG-conjugates, a tri-branched PEG-interferon (mPEG₃L₂-IFN) was synthesized by reacting a 30 KDa tri-branched mPEG₃L₂-NHS reagent with IFN to improve its pharmacokinetic properties and reduce the loss of in vitro bioactivity (which is generally exhibited by PEGylation) of the conjugated protein to some extent. The PEGylation procedure was optimized in terms of concentration and molar ratios of reactants, reaction time, temperature and pH conditions of the reaction mix. The conjugate was purified by cation exchange chromatography and characterized by SDS-PAGE and SE-HPLC. Trypsin digestion of mPEG₃L₂-IFN indicated a single site specificity of PEGylation. Anti viral bioactivity of mPEG₃L₂-IFN was found to be 2.38 × 10⁷ IU/mg which is approximately 9.52% of native IFNα2 (2.5 × 10⁸ IU/mg) and better than PEGasys from Roche Pharma. Therefore, it is reported that the tri-branched mPEG₃L₂-NHS reagent has the potential to be used to conjugate proteins for the promising therapeutic results.     

Possibilities of subunit localization with fluorescent protein tags and electron microscopy examplified by a cyanobacterial NDH-1 study

Cyanobacterial NDH-1 is a multisubunit complex involved in proton translocation, cyclic electron flow around photosystem I and CO₂ uptake. The function and location of several of its small subunits are unknown. In this work, the location of the small subunits NdhL, -M, -N, -O and CupS of Synechocystis 6803 NDH-1 was established by electron microscopy (EM) and single particle analysis. To perform this, the subunits were enlarged by fusion with the YFP protein. After classification of projections, the position of the YFP tag was revealed; all five subunits are integrated in the membrane domain. The results on NDH-1 demonstrate that a GFP tag can be revealed after data processing of EM data sets of moderate size, thus showing that this way of labeling is a fast and reliable way for subunit mapping in multisubunit complexes after partial purification.     

Sequence and Gene Expression Analyses of Plasmid pHPM8 from Helicobacter pylori Reveal the Presence of Two Operons with Putative Roles in Plasmid Replication and Antibiotic Activity

The DNA sequence of a 7.8-kb Helicobacter pylori plasmid, pHPM8, was determined. Six open reading frames (ORFs) were present. Ribonuclease protection studies showed that ORF1/ORF2 and ORF3/ORF4 genes are organized in operons possibly involved in plasmid replication and in production of a peptide with antibiotic activity, respectively. Finding areas of pHPM8 with a high level of identity to H. pylori chromosomal DNA supported the hypothesis that recombination occurs between plasmids and the chromosome of H. pylori.     

Secreted PCSK9 downregulates low density lipoprotein receptor through receptor-mediated endocytosis

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a protease that regulates low density lipoprotein receptor (LDLR) protein levels. The mechanisms of this action, however, remain to be defined. We show here that recombinant human PCSK9 expressed in HEK293 cells was readily secreted into the medium, with the prosegment associated with the C-terminal domain. Secreted PCSK9 mediated cell surface LDLR degradation in a concentration- and time-dependent manner when added to HEK293 cells. Accordingly, cellular LDL uptake was significantly reduced as well. When infused directly into C57B6 mice, purified human PCSK9 substantially reduced hepatic LDLR protein levels and resulted in increased plasma LDL cholesterol. When added to culture medium, fluorescently labeled PCSK9 was endocytosed and displayed endosomal-lysosomal intracellular localization in HepG2 cells, as was demonstrated by colocalization with DiI-LDL. PCSK9 endocytosis was mediated by LDLR as LDLR deficiency (hepatocytes from LDLR null mice), or RNA interference-mediated knockdown of LDLR markedly reduced PCSK9 endocytosis. In addition, RNA interference knockdown of the autosomal recessive hypercholesterolemia (ARH) gene product also significantly reduced PCSK9 endocytosis. Biochemical analysis revealed that the LDLR extracellular domain interacted directly with secreted PCSK9; thus, overexpression of the LDLR extracellular domain was able to attenuate the reduction of cell surface LDLR levels by secreted PCSK9. Together, these results reveal that secreted PCSK9 retains biological activity, is able to bind directly to the LDLR extracellular domain, and undergoes LDLR-ARH-mediated endocytosis, leading to accelerated intracellular degradation of the LDLR.     

Angiotensin-(1-7) prevents diabetes-induced cardiovascular dysfunction

The aim of this study was to test the hypothesis that treatment with angiotensin-(1-7) [ANG-(1-7)] or ANG-(1-7) nonpeptide analog AVE-0991 can produce protection against diabetes-induced cardiovascular dysfunction. We examined the influence of chronic treatment (4 wk) with ANG-(1-7) (576 microg.kg(-1).day(-1) ip) or AVE-0991 (576 microg.kg(-1).day(-1) ip) on proteinuria, vascular responsiveness of isolated carotid and renal artery ring segments and mesenteric bed to vasoactive agonists, and cardiac recovery from ischemia-reperfusion in streptozotocin-treated rats (diabetes). Animals were killed 4 wk after induction of diabetes and/or treatment with ANG-(1-7) or AVE-0991. There was a significant increase in urine protein (231 +/- 2 mg/24 h) in diabetic animals compared with controls (88 +/- 6 mg/24 h). Treatment of diabetic animals with ANG-(1-7) or AVE-0991 resulted in a significant reduction in urine protein compared with vehicle-treated diabetic animals (183 +/- 16 and 149 +/- 15 mg/24 h, respectively). Treatment with ANG-(1-7) or AVE-0991 also prevented the diabetes-induced abnormal vascular responsiveness to norepinephrine, endothelin-1, angiotensin II, carbachol, and histamine in the perfused mesenteric bed and isolated carotid and renal arteries. In isolated perfused hearts, recovery of left ventricular function from 40 min of global ischemia was significantly better in ANG-(1-7)- or AVE-0991-treated animals. These results suggest that activation of ANG-(1-7)-mediated signal transduction could be an important therapeutic strategy to reduce cardiovascular events in diabetic patients.     

Overexpression of human Hsp27 inhibits serum-induced proliferation in airway smooth muscle myocytes and confers resistance to hydrogen peroxide cytotoxicity

Airway smooth muscle (ASM) hypertrophy and hyperplasia are characteristics of asthma that lead to thickening of the airway wall and obstruction of airflow. Very little is known about mechanisms underlying ASM remodeling, but in vascular smooth muscle, it is known that progression of atherosclerosis depends on the balance of myocyte proliferation and cell death. Small heat shock protein 27 (Hsp27) is antiapoptotic in nonmuscle cells, but its role in ASM cell survival is unknown. Our hypothesis was that phosphorylation of Hsp27 may regulate airway remodeling by modifying proliferation, cell survival, or both. To test this hypothesis, adenoviral vectors were used to overexpress human Hsp27 in ASM cells. Cells were infected with empty vector (Ad5) or wild-type Hsp27 (AdHsp27 WT), and proliferation and death were assessed. Overexpressing Hsp27 WT caused a 50% reduction in serum-induced proliferation and increased cell survival after exposure to 100 microM hydrogen peroxide (H(2)O(2)) compared with mock-infected controls. Overexpression studies utilizing an S15A, S78A, and S82A non-phosphorylation mutant (AdHsp27 3A) and an S15D, S78D, and S82D pseudo-phosphorylation mutant (AdHsp27 3D) showed phosphorylation of Hsp27 was necessary for regulation of ASM proliferation, but not survival. Hsp27 provided protection against H(2)O(2)-induced cytotoxicity by upregulating cellular glutathione levels and preventing necrotic cell death, but not apoptotic cell death. The results support the notion that ASM cells can be stimulated to undergo proliferation and death and that Hsp27 may regulate these processes, thereby contributing to airway remodeling in asthmatics.