Virological and immunological determinants of intrahepatic virus-specific CD8+ T-cell failure in chronic hepatitis C virus infection

Virus-specific CD8+ T-cells play an important role in the outcome of acute hepatitis C virus (HCV) infection. In the chronic phase, however, HCV can persist despite the presence of virus-specific T-cell responses. Therefore, we set out to perform a full-breadth analysis of the intrahepatic virus-specific CD8+ T-cell response, its relation to the peripheral T-cell response, and the overall influence of viral escape and the genetic restriction on intrahepatic CD8+ T-cell failure. Intrahepatic and peripheral CD8+ T-cells from 20 chronically HCV infected patients (genotype 1) were comprehensively analyzed using overlapping peptides spanning the entire HCV polyprotein in concert with autologous viral sequences that were obtained for all targeted regions. HCV-specific CD8+ T-cell responses were detectable in most (90%) chronically HCV-infected patients, and two thirds of these responses targeted novel previously undescribed epitopes. Most of the responses were detectable only in the liver but not in the peripheral blood, indicating accumulation and enrichment at the site of disease. Of note, only approximately half of the responses were associated with viral sequence variations supported by functional analysis as viral escape mutations. Escape mutations were more often associated with HLA-B alleles. CONCLUSION: Our results show an unexpected high frequency of intrahepatic virus-specific CD8+ T-cells, a large part of which continue to target the present viral antigens. Thus, our results suggest that factors other than mutational escape contribute to the failure of intrahepatic virus-specific CD8+ T-cells.     

The plaque lipid lysophosphatidic acid stimulates platelet activation and platelet-monocyte aggregate formation in whole blood: involvement of P2Y1 and P2Y12 receptors

Despite the fact that lysophosphatidic acid (LPA) has been identified as a main platelet-activating lipid of mildly oxidized low-density lipoprotein (LDL) and human atherosclerotic lesions, it remains unknown whether it is capable of activating platelets in blood. We found that LPA at concentrations slightly above plasma levels induces platelet shape change, aggregation, and platelet-monocyte aggregate formation in blood. 1-alkyl-LPA (16:0 fatty acid) was almost 20-fold more potent than 1-acyl-LPA (16:0). LPA directly induced platelet shape change in blood and platelet-rich plasma obtained from all blood donors. However, LPA-stimulated platelet aggregation in blood was donor dependent. It could be completely blocked by apyrase and antagonists of the platelet adenosine diphosphate (ADP) receptors P2Y1 and P2Y12. These substances also inhibited LPA-induced aggregation of platelet-rich plasma and aggregation and serotonin secretion of washed platelets. These results indicate a central role for ADP-mediated P2Y1 and P2Y12 receptor activation in supporting LPA-induced platelet aggregation. Platelet aggregation and platelet-monocyte aggregate formation stimulated by LPA was insensitive to inhibition by aspirin. We conclude that LPA at concentrations approaching those found in vivo can induce platelet shape change, aggregation, and platelet-monocyte aggregate formation in whole blood and suggest that antagonists of platelet P2Y1 and P2Y12 receptors might be useful preventing LPA-elicited thrombus formation in patients with cardiovascular diseases.     

Peroxisome proliferator-activated receptor-gamma protects against hepatic ischemia/reperfusion injury in mice

The function of peroxisome proliferator-activated receptor-gamma (PPARgamma) in hepatic inflammation and injury is unclear. In this study, we sought to determine the role of PPARgamma in hepatic ischemia/reperfusion injury in mice. Male mice were subjected to 90 minutes of partial hepatic ischemia followed by up to 8 hours of reperfusion. PPARgamma was found to be constitutively activated in hepatocytes but not in nonparenchymal cells. Upon induction of ischemia, hepatic PPARgamma activation rapidly decreased and remained suppressed throughout the 8-hour reperfusion period. This reduced activation was not a result of decreased protein availability as hepatic nuclear PPARgamma, retinoid X receptor-alpha (RXRalpha), and PPARgamma/RXRalpha heterodimer expression was maintained. Accompanying the decrease in PPARgamma activation was a decrease in the expression of the natural ligand 15-deoxy-Delta(12,14)-prostaglandin J(2). This was associated with reduced interaction of PPARgamma and the coactivator, p300. To determine whether PPARgamma activation is hepatoprotective during hepatic ischemia/reperfusion injury, mice were treated with the PPARgamma agonists, rosiglitazone and connecting peptide. These treatments increased PPARgamma activation and reduced liver injury compared to untreated mice. Furthermore, PPARgamma-deficient mice had more liver injury after ischemia/reperfusion than their wild-type counterparts. Conclusion: These data suggest that PPARgamma is an important endogenous regulator of, and potential therapeutic target for, ischemic liver injury.     

APC promoter methylation and protein expression in hepatocellular carcinoma

Purpose We investigated the impact of promoter methylation on APC protein expression in patients with hepatocellular carcinoma (HCC). Materials and methods 50 patients [HCC (n=19), liver metastasis (n=19), cholangiocellular cancer (n=7), and benign liver tumors (n=5)] were studied for methylation using Methylight analysis. APC mutation was investigated by protein truncation test and direct sequencing of genomic DNA. The protein expression was evaluated by immunohistochemistry and Western blot analysis. Results The APC promoter was hypermethylated in 81.8% of non-cancerous liver tissue samples. All HCC samples and ten patients with liver metastasis (52.6%) exhibited APC promoter methylation. The degree of methylation was significantly higher in samples from HCC compared to the non-cancerous liver tissue samples (63.1% vs. 24.98%; p=0.001). The level of APC protein expression was significantly reduced in HCC samples compared to that of the corresponding non-tumor liver tissue (p<0.05). Conclusions Promoter methylation of the APC gene seems to be of significance in hepatocarcinogenesis and results in reduced protein expression in HCC. Interestingly, APC promoter methylation is also present in the vast majority of non-cancerous liver tissue whose (patho)physiological function remains unresolved.     

New therapies in acute decompensated heart failure

PURPOSE OF REVIEW: Hospitalization and mortality rates associated with heart failure are persistently high. This is due partly to aging of the population but mostly to delayed progress in the pharmacological treatment of decompensated heart failure. We will review the current recommendations and most recent advancement in the pharmacological treatment of acute decompensated heart failure while providing a systematic approach to the management of this prevalent condition. RECENT FINDINGS: Loop diuretics, nitrates and inotropes such as dobutamine and milrinone are the current mainstay of acute heart failure management although their associated morbidity and possible mortality have raised serious concerns. Recent vasoactive agents such as Nesiritide, Tolvaptan and more recently the inotropic agent Levosimedan could offer improved hemodynamics and congestive relief to patients in acute pulmonary edema. SUMMARY: Despite the promising results of these agents, further clinical trials are required prior to their international approval as first-line therapy. Although we can be optimistic that these vasoactive drugs might have favorable clinical outcomes and improve the intricate management of decompensated heart failure, their associated mortality benefit remains unclear and controversial.