Lipopolysaccharide augments expression and secretion of vascular endothelial growth factor in rat ventricular myocytes

Irbesartan has a curative effect on lipopolysaccharide-induced cardiotoxicity by antioxidant and antiapoptotic pathways

INTRODUCTION AND OBJECTIVE

Lipopolysaccharide (LPS) has been associated with myocardial inflammation, oxidative stress, apoptosis, and cardiac dysfunction, as well as death by causing sepsis. In this study, we investigated the effect of irbesartan (IRB), an angiotensin receptor antagonist, on cardiotoxicity caused by LPS.

METHODS

The experiment involved 24 Wistar albino rats divided into three groups of eight: control, LPS (5 mg/kg), and LPS (5 mg/kg)+IRB (3 mg/kg). Parameters including total oxidative status, total antioxidant status, oxidative stress index, and ischemia-modified albumin were measured to assess oxidative stress in heart tissues and serum. Serum CK, CK-MB, and LDH levels were measured spectrophotometrically. RT-qPCR was used to detect the mRNA expression levels of Bcl-2, BAX, p53, caspase-3, and sirtuin 1. Tissues taken from the heart and aorta were examined by immunohistochemistry and histopathology.

RESULTS

While there was an increase in the parameters indicating heart damage, oxidative stress, and apoptosis in the group given LPS, there was an improvement in all parameters and heart damage in the group treated with IRB.

CONCLUSION

As a result of our study, we determined that IRB has an ameliorating effect on myocardial damage caused by oxidative stress and apoptosis developed by the LPS-induced sepsis model.

Mitochondrial DNA induces inflammation and increases TLR9/NF-κB expression in lung tissue

Mitochondrial DNA (mtDNA) contains unmethylated CpG motifs that exhibit immune stimulatory capacities. The aim of this study was to investigate whether mtDNA activates the Toll-like receptor 9 (TLR9)/nuclear factor-κB (NF-κB) pathway, thereby contributing to post-traumatic systemic inflammatory response syndrome (SIRS) and lung injury in rats. The effects of mtDNA on macrophage culture were examined in order to elucidate the putative cellular mechanisms. Rats and macrophage cultures were treated with phosphate-buffered saline, nuclear DNA, or mtDNA for 2, 4, 8 and 24 h. Histological analysis of lung tissue was undertaken following hematoxylin and eosin staining, and cytokine levels were assessed by ELISA. NF-κB and IκB-α phosphorylation levels, as well as TLR9 protein expression were determined by western blot analysis; NF-κB, IκB-α and TLR9 mRNA levels were analyzed by RT-PCR. A greater degree of inflammation and lung injury was observed in response to mtDNA. In addition, mtDNA increased serum tumor necrosis factor-α, interleukin (IL)-6 and IL-10 levels in vivo and increased their secretion by cultured macrophages (p<0.05). In lung tissue, mtDNA increased NF-κB, IκB-α and TLR9 mRNA levels (p<0.05); it also increased phosphorylated NF-κB p65 and TLR9 protein levels in the macrophage cultures. Thus, mtDNA may be part of the danger-associated molecular patterns, contributing to the initiation of sterile SIRS through the activation of the TLR9/NF-κB pathway and the induction of pro-inflammatory cytokine production.

Assessment of control tissue for gene and protein expression studies: a comparison of three alternative lung sources

The use of an appropriate control group in human research is essential in investigating the level of a pathological disorder. This study aimed to compare three alternative sources of control lung tissue and to determine their suitability for gene and protein expression studies. Gene and protein expression levels of the vascular endothelial growth factor (VEGF) and gelatinase families and their receptors were measured using real-time reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemistry. The gene expression levels of VEGFA, placental growth factor (PGF), and their receptors, fms-related tyrosine kinase 1 (FLT1), and kinase insert domain receptor (KDR) as well as matrix metalloproteinase-2 (MMP-2) and the inhibitors, tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) and TIMP-2 were significantly higher in lung cancer resections. The gene expression level of MMP-9 was significantly lower in the corresponding samples. Altered protein expression was also detected, depending on the area assessed. The results of this study show that none of the three control groups studied are completely suitable for gene and protein studies associated with the VEGF and gelatinase families, highlighting the need for researchers to be selective in which controls they opt for.

LPS-induced vascular endothelial growth factor expression in rat lung pericytes

Vascular endothelial growth factor (VEGF) is a potent angiogenic and vascular permeability factor. Recent studies have shown that the VEGF levels increase in several cell types, for example, macrophages and smooth muscle cells after LPS stimulation, suggesting that it is important in the initiation and development of sepsis. In particular, LPS-regulated contractility in lung pericytes may play an important role in mediating pulmonary microvascular fluid hemodynamics during sepsis. This study investigated the production of VEGF by rat lung pericytes in response to LPS. LPS was found to enhance VEGF mRNA expression in a concentration-dependent manner peaking 2 h after stimulation in pericytes. Vascular endothelial growth factor protein levels in conditioned medium and in cell lysate also increased on increasing LPS and peaked after 24 to 48 h. LPS also significantly augmented iNOS expression in lung pericytes within 6 h. However, iNOS mRNA induction occurred later than LPS-induced VEGF mRNA increases. Interestingly, attempted inhibition with nuclear factor-kappaB or tyrosine kinase did not suppress LPS-induced augmented VEGF mRNA expression in lung pericytes, although both inhibitors markedly inhibited LPS-induced iNOS mRNA expression. SB203580, a p38 MAP kinase inhibitor, repressed LPS-induced VEGF mRNA expression. Furthermore, LPS stimulated a rapid and sustained phosphorylation of p38 MAP kinase. These results show that pericytes produce VEGF in response to LPS stimulation, and that this may be partly mediated by the p38 MAP kinase pathway. More research should be done to establish the regulation of capillary hemodynamics and identify mechanisms of their regulation.

Heat shock protein 70, heat shock protein 32, and vascular endothelial growth factor production and their effects on lipopolysaccharide-induced apoptosis in porcine aortic endothelial cells

Lipopolysaccharide (LPS) is a highly proactive molecule that causes in vivo a systemic inflammatory response syndrome and activates in vitro the inflammatory pathway in different cellular types, including endothelial cells (EC). Because the proinflammatory status could lead to EC injury and apoptosis, the expression of proinflammatory genes must be finely regulated through the induction of protective genes. This study aimed at determining whether an LPS exposure is effective in inducing apoptosis in primary cultures of porcine aortic endothelial cells and in stimulating heat shock protein (Hsp)70 and Hsp32 production as well as vascular endothelial growth factor (VEGF) secretion. Cells between third and eighth passage were exposed to 10 microg/mL LPS for 1, 7, 15, and 24 hours (time-course experiments) or to 1, 10, and 100 microg/mL LPS for 7 and 15 hours (dose-response experiments). Apoptosis was not affected by 1 microg/mL LPS but significantly increased in a dose-dependent manner with the highest LPS doses. Furthermore, apoptosis rate increased only till 15 hours of LPS exposure. LPS stimulated VEGF secretion in a dose-dependent manner; its effect became significant after 7 hours and reached a plateau after 15 hours. Both Hsp70 and Hsp32 expressions were induced by LPS in a dose-dependent manner after 7 hours. Subsequent studies were addressed to evaluate the protective role of Hsp32, Hsp70, and VEGF. Hemin, an Hsp32 inducer (5, 20, 50 microM), and recombinant VEGF (100 and 200 ng/mL), were added to the culture 2 hours before LPS (10 microg/mL for 24 hours); to induce Hsp70 expression, cells were heat shocked (42 degrees C for 1 hour) 15 hours before LPS (10 microg/mL for 24 hours). Hemin exposure upregulated Hsp32 expression in a dose-dependent manner and protected cells against LPS-induced apoptosis. Heat shock (HS) stimulated Hsp70 expression but failed to reduce LPS-induced apoptosis; VEGF addition did not protect cells against LPS-induced apoptosis at any dose tested. Nevertheless, when treatments were associated, a reduction of LPS-induced apoptosis was always observed; the reduction was maximal when all the treatments (HS + Hemin + VEGF) were associated. In conclusion, this study demonstrates that LPS is effective in evoking "the heat shock response" with an increase of nonspecific protective molecules (namely Hsp70 and Hsp32) and of VEGF, a specific EC growth factor. The protective role of Hsp32 was also demonstrated. Further investigations are required to clarify the synergic effect of Hsp32, Hsp70, and VEGF, thus elucidating the possible interaction between these molecules.

TNF-alpha and endotoxin increase hypoxia-induced VEGF production by cultured human nasal fibroblasts in synergistic fashion

OBJECTIVE

Vascular endothelial growth factor (VEGF) promotes angiogenesis and is associated with the invasion and metastasis of malignant tumors. It enhances vascular permeability and is expressed in inflammatory nasal as well as middle-ear mucosa. As the mechanism of VEGF induction during chronic inflammation, such as chronic paranasal sinusitis (CPS) remains to be clarified, we studied the factors regulating the production of VEGF in cultured human nasal fibroblasts and discussed the role of VEGF in the pathogenesis of CPS.

METHODS

We used ELISA to quantify VEGF levels in paranasal sinus effusions, nasal secretions, and serum from patients with CPS. In addition, we cultured human nasal fibroblasts isolated from nasal polyps of CPS patients and studied the effects of hypoxia, TNF-alpha, and endotoxin on their production of VEGF using ELISA and PCR.

RESULTS

The VEGF concentration was significantly higher in paranasal sinus effusions than in nasal secretions and serum. Nasal fibroblasts produced high levels of VEGF, when cultured under hypoxic condition and this production was remarkably enhanced in the presence of TNF-alpha or endotoxin.

CONCLUSION

VEGF is locally produced in paranasal sinuses as well as nasal mucosa and its production is increased in patients with CPS. Hypoxia is associated with the production of VEGF by nasal fibroblasts and TNF-alpha and endotoxin may act synergistically to enhance VEGF production in paranasal sinuses under hypoxic condition.

Purified protein derivative of tuberculin upregulates the expression of vascular endothelial growth factor in T lymphocytes in vitro

The purpose of this study was to investigate the cellular source and significance of vascular endothelial growth factor (VEGF) which, as reported previously, is elevated in the sera of pulmonary tuberculous patients. We obtained peripheral blood mononuclear cells (PBMCs) from 28 patients with active pulmonary tuberculosis, from 11 healthy controls who were positive for purified protein derivative of tuberculin (PPD), and from eight healthy individuals who were negative for PPD. We incubated the PBMCs with PPD in the presence or absence of major histocompatibility (MHC) class I or class II antibody in vitro, and measured the VEGF levels of culture supernatants. We also analysed the source of cells that secrete VEGF by using flow cytometry with intracellular staining. The T lymphocytes of active tuberculous patients secreted a higher level of VEGF than those of healthy controls. This production of VEGF was inhibited by adding MHC class II antibody. The addition of MHC class I antibody, however, did not inhibit. We propose that CD4+ T lymphocytes are almost certainly the cells that produce VEGF in response to PPD. VEGF production might be associated with an antigen-specific immune reaction via CD4+ T lymphocytes in tuberculosis.

Prostaglandin E(2) modulation of vascular endothelial growth factor production in murine macrophages

We have previously shown that dietary (n-3) fatty acids decrease mammary tumor vascularization and PGE(2) production. One possible mechanism may be the modulation of vascular endothelial growth factor (VEGF) production by PGE(2). Macrophages are major producers of VEGF, and thus we assessed the role of PGE(2) in vitro and in vivo on their VEGF production. When added to macrophages, pharmacological (10(-7) M) but not physiological (10(-9) to 10(-11) M) concentrations of PGE(2) increased VEGF mRNA and protein levels. That increased expression was relatively rapid and sustained up to 8 hrs, but declined by 24 hrs. Similarly, dibutryl cAMP increased production of VEGF protein which was completely inhibited by H89. Addition of cAMP-elevating agents further potentiated the production of VEGF by PGE(2). Next, (n-3) and (n-6) fatty acids were added to macrophages in vitro or provided in the diet. Macrophages of mice fed safflower oil (n-6) had 2- to 4-fold greater copy number of VEGF transcripts after lipopolysaccarhide (LPS) stimulation compared to fish oil (n-3). A decreasing trend was seen in LPS-induced VEGF secretion from macrophages in vitro after docosahexaenoic acid or eicosapentaenoic acid incubation compared to arachidonic acid. While pharmacological concentrations of PGE(2) modulate VEGF expression, physiological alterations did not alter VEGF protein production by macrophages.