Mechanisms by which acute phase proteins enhance development of liver fibrosis: effects on collagenase and prolyl-4-hydroxylase activity in the rat liver

Double-Negative T Cells Regulate Hepatic Stellate Cell Activation to Promote Liver Fibrosis Progression via NLRP3

Aim

We mainly explored the role and mechanism of double-negative T cells (DNTs) in liver fibrosis.

Methods

DNTs were co-cultured with mouse hepatic stellate cells (HSCs). Later, cell viability was detected by Cell Counting Kit-8 (CCK-8) assay; α-SMA expression was measured through fluorescence staining; TNF-α, IL-6, and MMP-9 levels were measured by ELISA; and the expression of Bcl-2, TGF-β1, NLRP3, ASC, and TNFR1 proteins in HSCs was detected by Western blotting (WB) assay. At the same time, HSC-NLRP3-/- and HSC-TNFR1-/- are used to explore the mechanism. In mouse experiments, mice were intraperitoneally injected with DNTs; afterward, the hepatic tissue fibrosis degree was detected by Masson staining, α-SMA expression was measured through immunohistochemistry (IHC) assay, and histopathological changes were detected by sirius-red staining and H&E staining.

Results

The results suggested that DNTs promoted HSC activation and NLRP3 activation. The effect of DNTs on activating HSC-NLRP3-/- was suppressed, and the difference was significant as compared with HSCs. HSC-TNFR1-/- activation was also inhibited. To explore the mechanism of DNT-secreted TNF-α in TNFR1-NLRP3 activation, we transfected DNTs with TNF-α siRNA; as a result, DNTs with TNF-α silencing did not significantly affect HSC activation. DNTs promoted hepatic tissue fibrosis progression and HSC activation; after treatment with NLRP3 inhibitor, the effect of DNTs on promoting fibrosis was suppressed.

Conclusion

We discovered that DNTs played an important role in liver fibrosis and that DNTs promoted HSC activation via the TNF-α-TNFR1-NLRP3 signal axis, thus further promoting liver fibrosis progression.

Skin Protein Profile after Major Weight Loss and Its Role in Body Contouring Surgery

Chronic inflammation during morbid obesity significantly alters cutaneous tissue. Large weight loss achieved after bariatric surgery minimizes or halts damage caused by metabolic syndrome, but further deteriorates the clinical condition of skin. Postbariatric skin flaccidity produces major difficulties to plastic surgery. In this study, we analyzed differences in protein composition of the skin between patients with morbid obesity and those after large weight loss and established correlations between differentially expressed proteins and clinical characteristics of postbariatric skin tissue, to improve body contouring surgery techniques.

Accelerated development of liver fibrosis in CCl4-treated rats by the weekly induction of acute phase response episodes: upregulation of alpha1(I) procollagen and tissue inhibitor of metalloproteinase-1 mRNAs

Patients with alcoholic hepatitis have several manifestations of the acute phase response (APR) and have elevated blood levels of interleukin-1, interleukin-6 and tumor necrosis factor-alpha. We have previously shown that liver stellate cells express interleukin-6 mRNA and protein and respond to this cytokine with increased expression of alpha1(I) procollagen mRNA. We further showed that the production of an APR episode stimulates a transient expression of alpha1(I) procollagen mRNA in the liver. In this communication we demonstrate that the concomitant induction of a weekly APR episode in rats with a schedule of CCl4 to produce cirrhosis, accelerates the development of liver fibrosis. We show that the enhancement of liver fibrosis is due, in part, to further upregulation in the expression of alpha1(I) procollagen and tissue inhibitor of metalloproteinases-1 mRNAs above values observed in control rats receiving only CCl4. The effect of the APR appears to have specificity since not all the mRNAs measured were equally affected. Altogether, these results suggest that increased blood or liver levels of APR cytokines, whether induced by APR episodes, endotoxin or other unrelated causes, may contribute to the development of liver fibrosis by enhancing the expression of type I collagen and of tissue inhibitor of metalloproteinases-1 mRNAs.

Fibrogenesis in cirrhosis. Potential for therapeutic intervention

Liver cirrhosis is an end stage of several diseases that affect the liver chronically. It is characterized, among other things, by excess collagen deposition, distortion of liver architecture, tissue malfunction and hemodynamic alterations. Many of the complications of cirrhosis may result from excess matrix-deposition. Therefore, prevention of collagen accumulation or removal of collagen deposits could ameliorate the disease. In this article we discuss the pathophysiology of liver fibrosis and we describe various compounds with antiinflammatory and antifibrogenic activity. We discuss their possible mechanism of action and we describe animal and clinical studies in which these compounds have been utilized.

Effect of acute phase proteins, especially alpha 2-macroglobulin, on granuloma formation around Schistosoma mansoni eggs in the rat

A new model for the study of granuloma formation in the liver is described. Rats received an injection of 20,000 Schistosoma mansoni eggs in the portal vein and granuloma formation was evaluated at 3, 5 and 7 weeks post-injection. Liver collagen was estimated at the same time and serum procollagen III peptide, a marker of collagenesis, weekly. With this model, wherein the number of S. mansoni eggs and the time of injury are standardized, the effect of high levels of acute phase proteins especially alpha 2-macroglobulin on granuloma formation was studied. It appeared that in rats with high levels of alpha 2-macroglobulin the mean size of granulomas was significantly greater at 3 and 5 weeks compared with controls. In both groups an increase in liver collagen was observed during this period, reaching a peak at 5 weeks in the acute phase group. This model facilitates the study of the effects of S. mansoni eggs on granuloma formation.

Collagenase of hepatocytes and sinusoidal liver cells in the reversibility of experimental cirrhosis of the liver

In order to explore the cellular source(s) and the behaviour of the collagenolytic activity previously described in rat liver homogenates, in the reversibility of experimental cirrhosis of the liver, enriched suspensions of hepatocytes and of sinusoidal liver cells were obtained by a procedure which employs low EDTA concentrations and no bacterial collagenase. Cell suspensions were prepared from three different groups of animals: 1) normal controls, 2) rats with CCl4-induced cirrhosis of the liver, and 3) rats with swine serum-induced cirrhosis of the liver. Animals were sacrificed in each group upon completion of treatment and also after 3, 6 and 12 months. In each liver wet weight and collagen concentration were determined, and collagenolytic activity of both enriched cell suspensions was measured separately. In addition, histological studies of liver tissue and ultrastructural examination of cell suspensions were performed by standard procedures. Enriched suspensions of both normal hepatocytes and sinusoidal liver cells display Ca2(+)-dependent collagenolytic activities. Both cell suspensions obtained from each of the two types of cirrhotic livers show normal or slightly increased average levels of collagenase activity at the time of treatment discontinuation, when average liver collagen content ranges from 6 to 10-fold over normal, suggesting that the normal collagenase/collagen ratio is disturbed and that collagenolytic activity is deeply decreased in relation to the actual liver collagen load.(ABSTRACT TRUNCATED AT 250 WORDS)

Alpha 2-macroglobulin and fibrinogen modulate inflammatory edema in man

Animal experiments suggest that the response of acute-phase proteins (APPs) modulates the inflammatory reaction following tissue injury. To study this in man we investigated the relation between a number of APPs, including fibrinogen and alpha 2-macroglobulin, and the inflammatory edema induced by a primary immunization against cholera, typhoid, and yellow fever. Vaccination induces a significant APP response; however, only alpha 2-macroglobulin and fibrinogen were of importance to the amount of edema, measured 24 h after vaccination. High plasma levels of alpha 2-macroglobulin strongly inhibit the amount of edema, whereas a high level of fibrinogen proved to be a stimulating factor. This holds both for the basal prevaccination levels and the postvaccination levels. The normal variation of the plasma concentration of these proteins in healthy subjects seems to be a determining factor to the amount of edema in this kind of injury.

Relation between acute-phase proteins and enhanced bleomycin-induced pulmonary fibrosis in the rat

Intratracheal application of Bleomycin (Bleo) in rats induces interstitial pneumonitis followed by progressive fibrosis. As the presence of high levels of acute-phase proteins (= reactants = APR), especially alpha 2-macroglobulin of the rat (alpha 2M), enhances liver fibrosis, we investigated whether this phenomenon also occurs in rats with Bleo-induced lung fibrosis. The experiments showed that this is the case; lung fibrosis assessed by measuring hydroxyproline, hexosamine, and prolyl-4-hydroxylase was enhanced when just before Bleo application an acute-phase reaction was induced. This effect can be explained by the inhibitory effect of alpha 2M on collagenase. The experiments showed a significant positive correlation between alpha 2M and parameters of fibrosis. This is especially the case in the third week after Bleo application. Bleo itself does not induce a strong acute-phase reaction, notwithstanding the pneumonitis during the first weeks. The increased fibrosis is accompanied by progressive ventilatory disturbances demonstrated by high arterial pCO2 and low pO2. In patients undergoing Bleo treatment, varying levels of APR can be expected, and this could explain the rapid development of fibrosis in individual cases.

Collagenolytic activity in experimental cirrhosis of the liver

Collagenolytic activity has been measured in insoluble sediments of normal and CCl4-induced cirrhotic rat liver. Two techniques were used: in one assay, the insoluble liver sediments were incubated with a radioactively labeled exogenous substrate; in the other assay, the endogenous collagen present in the insoluble liver sediments served as the substrate. Animals in various stages of development of CCl4-induced cirrhosis were used. Results suggest that in rat liver cirrhosis collagenolytic activity assayed with both techniques appears to increase when expressed as weight of collagen degraded in 24 hr. On the other hand, when the data are corrected for the variable amounts of collagen present in the insoluble liver sediments and expressed as weight of collagen degraded in 24 hr per unit weight of total collagen incubated, collagenolytic activity is shown to be significantly decreased below the normal level and to remain so for prolonged periods.