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E Titos

Publications and source records attributed to E Titos.

8 recordsLinked to original sources
PubMed2004

Cigarette smoke concentrate increases 8-epi-PGF2alpha and TGFbeta1 secretion in rat mesangial cells.

Epidemiological studies have shown that cigarette smoke, an oxidant agent, is a risk factor for the development of diabetic nephropathy (DN), in which pathogenesis transforming growth factor beta(1) (TGFbeta(1)) plays a key role. In our experimental model we exposed mesangial cell cultures to cigarette smoke concentrate (CSC) to study the effect of smoking on the pathogenesis of DN. Thus, we analyzed the effect of CSC on TGFbeta(1) and lipid peroxidation (8-epi-PGF(2alpha)) in rat mesangial cells. Furthermore, since the protein kinase C (PKC) pathway appears to be a key factor for the enhanced production of TGFbeta(1), we also analyzed the effect of the selective PKCbeta inhibitor LY379196 on TGFbeta(1) response to CSC. CSC induced an increase of both TGFbeta(1) and 8-epi-PGF(2) compared to basal conditions (5 mM glucose). The CSC-induced increase in TGFbeta(1) secretion was significantly suppressed by LY379196. These data suggest that smoking could increase TGFbeta(1) production, probably due to oxidative stress and PKCbeta activation. This finding supports the concept that smoking is a risk factor for DN development.

Animals↗
PubMed2004

[Kupffer cell].

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Humans↗
PubMed2000

Hepatocyte-derived cysteinyl leukotrienes modulate vascular tone in experimental cirrhosis.

BACKGROUND & AIMS: The leukotrienes C(4)/D(4)/E(4) (cysteinyl-LTs) are 5-lipoxygenase (5-LO)-derived eicosanoids with potent vasoconstrictor, proliferative, and profibrogenic properties that may participate in key pathophysiologic events in liver cirrhosis. We examined the cysteinyl-LT biosynthetic pathway in liver tissue and purified liver cells isolated from rats with carbon tetrachloride-induced cirrhosis, and assessed the vasoactive properties of LTD(4) in hepatic stellate cells (HSCs) and anesthetized rats. METHODS & RESULTS: Liver homogenates from cirrhotic rats had increased 5-LO mRNA and cysteinyl-LT content, as determined by Northern blot and enzyme immunoassay, respectively. In isolated rat liver cells, 5-LO mRNA expression was found to be restricted to Kupffer cells. However, among the liver cells (i.e., hepatocytes, Kupffer cells, HSCs, and sinusoidal endothelial cells), hepatocytes exhibited the highest ability to generate cysteinyl-LTs from the unstable intermediate LTA(4). Hepatocytes from cirrhotic rats showed an enhanced baseline generation of cysteinyl-LTs, but their ability to synthesize cysteinyl-LTs from exogenous LTA(4) was found to be similar to that of hepatocytes from normal animals. Both LTD(4) and hepatocyte-conditioned medium increased intracellular Ca(2+) concentration and induced contraction in HSCs, suggesting that hepatocyte-derived cysteinyl-LTs could act in a paracrine fashion on nearby nonparenchymal liver cells. The relevance of these in vitro findings was further established in vivo by the observation that LTD(4) significantly increased portal pressure in anesthetized rats. CONCLUSIONS: These data suggest a role for hepatocyte-derived cysteinyl-LTs in mediating hepatic vascular tone abnormalities in cirrhosis.

Animals↗
PubMed1999

Atrial natriuretic peptide antagonizes endothelin-induced calcium increase and cell contraction in cultured human hepatic stellate cells.

Hepatic stellate cells (HSCs) participate in the regulation of hepatic microcirculation and have receptors for many vasoconstrictor factors. It is unknown whether HSCs have receptors for circulating vasodilators such as atrial natriuretic peptide (ANP). This study investigated the presence of ANP receptors in human HSCs and whether ANP antagonizes the effects of endothelin-1 in these cells. ANP receptors were assessed by binding and cross-linking studies, reverse-transcriptase polymerase chain reaction (PCR), and measuring intracellular cyclic guanosine monophosphate concentration. Intracellular calcium concentration ([Ca(2+)](i)) and cell contraction were measured in individual cells loaded with fura-2 using a morphometric method. Binding and cross-linking affinity experiments showed the existence of ANP receptors in human HSCs. PCR products with the expected length were obtained for guanylate cyclase A receptor, the physiological receptor of ANP, both in quiescent and activated human cells. ANP induced a dose-dependent increase in intracellular cyclic guanosine monophosphate concentration and blunted the increase in [Ca(2+)](i) elicited by endothelin-1. Most importantly, ANP markedly reduced cell contraction induced by endothelin-1. HSCs isolated from rats with carbon tetrachloride-induced cirrhosis showed a higher number of ANP receptors compared with HSCs isolated from normal rats, indicating that in vivo activation of HSCs is associated with an up-regulation of ANP receptors. These results indicate that human HSCs have receptors for ANP, the activation of which reduces the effects of endothelin-1 on [Ca(2+)](i) and cell contraction. ANP could participate in regulating the contractility of HSCs by antagonizing the effect of vasoconstrictors.

Animals↗
PubMed1999

Selective inhibition of cyclooxygenase 2 spares renal function and prostaglandin synthesis in cirrhotic rats with ascites.

BACKGROUND & AIMS: The critical role of cyclooxygenase (COX) products in maintenance of renal function in cirrhosis with ascites discourages the use of nonsteroidal anti-inflammatory drugs in this disease. The recent development of selective COX-2 inhibitors opens new avenues for the use of these compounds in decompensated cirrhosis. The current study evaluates the effects of a selective COX-2 inhibitor (SC-236) on renal function in cirrhotic rats with ascites. METHODS: In protocol 1, urine volume, urinary excretion of sodium and prostaglandins, glomerular filtration rate, and renal plasma flow were measured before and after administration of SC-236 (n = 12) or ketorolac (n = 10) to rats with cirrhosis. Protocol 2 was aimed at assessing the effects of COX inhibitors on renal water metabolism in 28 cirrhotic rats. RESULTS: Administration of SC-236 to cirrhotic animals did not produce significant renal effects, whereas administration of the nonselective COX-1/COX-2 inhibitor, ketorolac, resulted in a marked reduction in urine volume, urinary excretion of prostaglandins, and glomerular filtration rate and in a significant impairment in renal water metabolism. CONCLUSIONS: These findings indicate that SC-236 does not significantly impair renal function in rats with cirrhosis.

Animals↗
PubMed1999

Hepatocytes are a rich source of novel aspirin-triggered 15-epi-lipoxin A(4).

Novel aspirin (ASA)-triggered 15-epi-lipoxins (ATL) comprise new potent bioactive eicosanoids that may contribute to the therapeutic effect of this drug. ATL biosynthesis is initiated by ASA acetylation of cyclooxygenase (COX)-2 and was originally identified during the interaction of leukocytes with either endothelial or epithelial cells. Here, we examined ATL biosynthesis in rat hepatocytes either alone or in coincubation with nonparenchymal liver cells (NPC) and in liver homogenates from ASA-treated rats. Rat hepatocytes and CC-1 cells, a rat hepatocyte cell line, displayed COX-1 but not COX-2 mRNA expression and predominantly produced thromboxane A(2) (TXA(2)) and 15-hydroxyeicosatetraenoic acid (15-HETE). In these cells, ASA shifted the arachidonic acid metabolism from TXA(2) to 15-HETE in a concentration-dependent manner. In contrast, neither indomethacin, ibuprofen, valeryl salicylate, nor nimesulide was able to trigger 15-HETE biosynthesis. SKF-525A, a cytochrome P-450 inhibitor, significantly reduced the effect of ASA on 15-HETE biosynthesis. Furthermore, phenobarbital, a potent inducer of cytochrome P-450 activity, further increased ASA-induced 15-HETE production. ASA treatment of hepatocyte-NPC coincubations resulted in the generation of significant amounts of ATL. In addition, in vivo experiments demonstrated augmented hepatic levels of 15-epi-lipoxin A(4) in ASA-treated rats. Taken together and considering that ASA is hydrolyzed on its first pass through the portal circulation, these data indicate that, during ASA's consumption, liver tissue generates biologically relevant amounts of ATL by COX-2-independent mechanisms.

Animals↗
PubMed1998

Altered biosynthesis of leukotrienes and lipoxins and host defense disorders in patients with cirrhosis and ascites.

BACKGROUND & AIMS: Advanced cirrhosis is associated with impaired leukocyte function, but the mechanism underlying this host defense alteration is unknown. The aim of this study was to investigate the lipoxygenase pathway of arachidonic acid metabolism and its influence in leukocyte trafficking in patients with cirrhosis and ascites. METHODS: Neutrophils (polymorphonuclear leukocytes [PMN]) were isolated from patients with cirrhosis and ascites and healthy subjects, and 5-lipoxygenase (5-LO) messenger RNA levels and 5-LO-derived products were measured. The effect of leukotrienes (LT) and lipoxins (LX) on PMN adhesion and migration was also assessed. RESULTS: PMN from patients with cirrhosis showed increased 5-LO messenger RNA expression. However, in vitro generation of LTB4, cysteinyl-containing LT and LX was significantly decreased in cirrhotic patients. Interestingly, a close relationship between the activity of the renin-angiotensin system and LXA4 biosynthesis was observed both in vitro and in vivo. PMN isolated from cirrhotic patients with ascites showed significantly decreased adhesion and migration in response to LTB4. LXA4 did not provoke PMN adhesion and migration, but rather abrogated the differences between control and cirrhotic PMN. Cirrhotic monocytes showed marked impairment in adherence to laminin when stimulated with either LTB4 or LXA4. CONCLUSIONS: These results show the existence of altered biosynthesis of LT and LX and defective response to these lipoxygenase products in leukocytes from patients with cirrhosis and ascites. This abnormality may be relevant to the pathogenesis of host defense disorders in chronic liver disease.

Angiotensin II↗