Growth hormone upregulates intestinal trefoil factor expression in the ileum of rats after γ-radiation

Growth hormone (GH) and intestinal trefoil factor (ITF) have been involved in intestinal protection and repair. This study investigates the effects of GH administration on ITF expression and histological changes associated with tissue injury in an intestinal rat model of radiation. Adult male rats were divided into four groups: control, GH, radiation and radiation + GH (GHyRAD). Ileum samples were obtained at 2 or 72 h after radiation and processed to determine ITF levels (mRNA and protein) by quantitative polymerase chain reaction, Western blot and immunohistochemistry. In addition, goblet ITF-positive cells were identified by immunohistochemistry at 72 h. Our results showed an upregulation of mRNA and protein production of ITF in ileum samples after GH and radiation + GH compared with control and irradiated samples. Irradiation alone affected ITF protein expression. However, irradiation after GH pretreatment produced the highest ITF mRNA and protein levels at both the tested time points. ITF-producing goblet cells were identified in intestinal villi (apical location). GH treatment increased the number of ITF-producing goblet cells, and radiation after GH treatment displayed further increase in the number of ITF-positive goblet cells. GH upregulates ITF in normal intestinal tissue. This upregulation is higher when radiation is given after GH treatment. Nevertheless, the mechanism by which GH regulates ITF expression remains unclear and is still under investigation. These results could open up new avenues in the therapeutic reparative and protective effects of GH during radiotherapy and chemotherapy.

Effects of mannoprotein E1 in liquid diet on inflammatory response and TLR5 expression in the gut of rats infected by Salmonella typhimurium

Background

Mannoproteins are yeast cell wall componend, and rich in mannose. The use of foods rich in mannose as carbohydrate, could have a bioprotective effect against entrobacteria intestinal infection. Nothing is known about mannoproteins' activity in inflammatory bowel processes induced by entrobacteria.

This study investigates the effects of mannoprotein administration via a liquid diet on inflammatory response and TLR5 expression during intestinal tissue injury in a rat model of infection with Salmonella typhimurium.

Methods

Adult Wistar male rats were divided into three groups: control, and mannoprotein E₁ at 10 or 15%. Animals were fed with a liquid diet supplemented or not with mannoprotein E₁. Groups were infected by intragastrical administration of S. typhimurium. 24 h post-inoculation samples of spleen, ileum and liver were collected for microbiological studies. Gut samples were processed to determine levels of proinflammatory cytokines (mRNA) and TLR5 (mRNA and protein) by quantitative PCR and Western-blot, and the number of proliferative and apoptotic cells determined by immunohistochemistry.

Results

Ininfected levels of proinflammatory cytokines and TLR5 were higher in untreated controls than in the animals receiving mannoprotein. Proliferation was similar in both groups, whereas apoptosis was higher in controls. Curiosly, the mannoprotein effect was dose dependent.

Conclusions

Mannoprotein administration in a liquid diet seems to protect intestinal tissue against S. typhimurium infection. This protection seems to expressed as a lower pro-inflammatory response and TLR5 downregulation in gut epithelium, as well as by an inhibition of apoptosis. Nevertheless, the molecular mechanism by which mannoprotein is able to regulate these responses remain unclear. These results could open up new avenues in the use of mannoproteins as prebiotics in the therapeutic strategy for treatment of inflammatory gut processes induced by microbia.

Factors involved in the progress of preclinical atherosclerosis associated with systemic lupus erythematosus: a 2-year longitudinal study

Objectives

To assess the changes in carotid intima-media thickness (IMT) and the associated risks factors in patients with low severity systemic lupus erythematosus (SLE).

Methods

Common carotid IMT measurements were obtained by ultrasound from 101 patients with SLE at an interval of 2 years. Cardiovascular risk factors, disease activity, accumulated damage, severity (Katz index) and biochemical parameters (including high sensitivity C-reactive protein, interleukin 6, C3a, C4a, C5a and homocysteine) were also assessed. Multiple linear regression was used to assess the effect of these variables on the end IMT measurement (eIMT) adjusted to the baseline measurement (bIMT).

Results

The cohort comprised 94.1% women, with a mean age at entry of 41.5 years and a mean disease duration of 12.1 years. An increase of 0.078 mm in IMT was detected over 2 years, from a mean bIMT of 0.37 mm to a mean eIMT of 0.44 mm (p<0.001). When adjusted for the bIMT, multiple linear regression identified bIMT, age at diagnosis, homocysteine, C3 and C5a as risk factors for IMT progression.

Conclusions

IMT significantly increases over 2 years in patients with SLE. Age, baseline IMT, C3, C5a anaphylatoxin and homocysteine are all associated risk factors, supporting a role for complement and homocysteine in the early stages of premature SLE-associated atherosclerosis.

The epidermal growth factor receptor tyrosine kinase phosphorylates connexin32

The epidermal growth factor (EGF) receptor purified by calmodulin-affinity chromatography from solubilized rat liver plasma membranes phosphorylates connexin32 in gap junction plaques isolated from the same origin. Phosphorylation of connexin32 was stimulated by EGF and mainly occurs at tyrosine residue(s), although phosphorylation of serine and threonine residues was also detected. The kinetics parameters for the phosphorylation of connexin32 parallel those for the transphosphorylation of the EGF receptor. m-Calpain proteolyzes phosphoconnexin32, and its major 26 kDa proteolytic fragment only contains phosphotyrosine residue(s). Calmodulin binds to connexin32 in the absence of calcium and prevents in great extent its phosphorylation by the EGF receptor tyrosine kinase.

Phosphorylation of connexin-32 by protein kinase C prevents its proteolysis by mu-calpain and m-calpain

Isolated connexin-32s from rat and mouse liver are proteolyzed in vitro by the intracellular Ca(2+)-dependent neutral proteases, mu-calpain and m-calpain, producing a major fragment of 26 kDa. Connexin-26 is not proteolyzed by calpain. Calpain cleaves connexin-32 at its C-terminal end as shown by 125I-calmodulin binding experiments. Connexin-32, but not connexin-26, is phosphorylated by both protein kinase A and protein kinase C in serine residues and the sites of phosphorylation by both kinases remain in the major 26-kDa fragment resulting from calpain proteolysis. Phosphorylation of connexin-32 by protein kinase C, but not by protein kinase A, prevents the proteolytic attack of mu-calpain and m-calpain. Phosphorylation of connexin-32 by protein kinase A and protein kinase C does not prevent its proteolysis by papain, alpha-chymotrypsin, proteinase K, and trypsin.