Granzyme B-dependent proteolysis acts as a switch to enhance the proinflammatory activity of IL-1α.

Granzyme B is a cytotoxic lymphocyte-derived protease that plays a central role in promoting apoptosis of virus-infected target cells, through direct proteolysis and activation of constituents of the cell death machinery. However, previous studies have also implicated granzymes A and B in the production of proinflammatory cytokines, via a mechanism that remains undefined. Here we show that IL-1α is a substrate for granzyme B and that proteolysis potently enhanced the biological activity of this cytokine in vitro as well as in vivo. Consistent with this, compared with full-length IL-1α, granzyme B-processed IL-1α exhibited more potent activity as an immunoadjuvant in vivo. Furthermore, proteolysis of IL-1α within the same region, by proteases such as calpain and elastase, was also found to enhance its biological potency. Thus, IL-1α processing by multiple immune-related proteases, including granzyme B, acts as a switch to enhance the proinflammatory properties of this cytokine.

Suppression of interleukin-33 bioactivity through proteolysis by apoptotic caspases.

Interleukin-33 (IL-33) is a member of the IL-1 family and is involved in polarization of T cells toward a T helper 2 (Th2) cell phenotype. IL-33 is thought to be activated via caspase-1-dependent proteolysis, similar to the proinflammatory cytokines IL-1 beta and IL-18, but this remains unproven. Here we showed that IL-33 was processed by caspases activated during apoptosis (caspase-3 and -7) but was not a physiological substrate for caspases associated with inflammation (caspase-1, -4, and -5). Furthermore, caspase-dependent processing of IL-33 was not required for ST2 receptor binding or ST2-dependent activation of the NF-kappaB transcription factor. Indeed, caspase-dependent proteolysis of IL-33 dramatically attenuated IL-33 bioactivity in vitro and in vivo. These data suggest that IL-33 does not require proteolysis for activation, but rather, that IL-33 bioactivity is diminished through caspase-dependent proteolysis within apoptotic cells. Thus, caspase-mediated proteolysis acts as a switch to dampen the proinflammatory properties of IL-33.

Impact of Tenofovir on Hepatitis Delta Virus Replication in the Swiss Human Immunodeficiency Virus Cohort Study.

We analyzed changes in hepatitis B virus and hepatitis delta virus (HDV) viral loads (VL) during tenofovir-containing antiretroviral therapy among patients with a replicating HDV infection in the Swiss HIV Cohort Study. Only 28.6% experienced a ≥2.0 log reduction in HDV RNA, and 14.3% had undetectable HDV VL within 5 years.

Hepatitis delta-associated mortality in HIV/HBV-coinfected patients.

BACKGROUND & AIMS: Hepatitis delta virus (HDV) infection accelerates the progression of hepatitis B virus (HBV)-related liver disease. We assessed the epidemiological characteristics of HDV infection in the nationwide Swiss HIV Cohort Study and evaluated its impact on clinical outcomes. METHODS: All HIV-infected patients with a positive hepatitis B surface antigen test were considered and tested for anti-HDV antibodies. HDV amplification and sequencing were performed in anti-HDV-positive patients. Demographic and clinical characteristics at initiation of antiretroviral therapy, as well as causes of death were compared between HDV-positive and HDV-negative individuals using descriptive statistics. Kaplan-Meier and multivariable Cox regression analyses were used to evaluate the association between HDV infection and overall mortality, liver-related mortality as well as incidence of hepatocellular carcinoma (HCC). RESULTS: Of 818 patients with a positive hepatitis B surface antigen tests, 771 (94%) had a stored serum sample available and were included. The prevalence of HDV infection was 15.4% (119/771, 95% CI: 12.9-18.0) and the proportion of HDV-positive patients with HDV replication 62.9% (73/116). HDV-infected patients were more likely to be persons who inject drugs (60.6% vs. 9.1%) and to have a positive hepatitis C virus (HCV) serology (73.1% vs. 17.8%) compared to HDV-uninfected ones. HDV infection was strongly associated with overall death (adjusted hazard ratio 2.33, 95% CI 1.41-3.84), liver-related death (7.71, 3.13-18.97) and with the occurrence of HCC (9.30, 3.03-28.61). Results were similar when persons who inject drugs or HCV-coinfected patients were excluded from the analyses. CONCLUSIONS: The prevalence of HDV in hepatitis B surface antigen-positive patients in the Swiss HIV Cohort Study (SHCS) is high and HDV infection is independently associated with mortality and liver-related events, including HCC. LAY SUMMARY: Hepatitis delta virus (HDV) infection accelerates the progression of hepatitis B virus (HBV)-related liver disease. In a nationwide cohort of HIV-infected individuals in Switzerland, 15% of HBV-coinfected patients had antibodies to HDV infection, of which a majority had active HDV replication. HDV-infected individuals were 2.5 times more likely to die, eight times more likely to die from a liver-related cause and nine times more likely to develop liver cancer compared to HDV-uninfected ones. Our results emphasize the need for prevention programs (including HBV vaccination), the systematic screening of at risk populations as well as close monitoring, and underline the importance of developing new treatments for chronic HDV infection.

Caspase-1 promiscuity is counterbalanced by rapid inactivation of processed enzyme.

Members of the caspase family of cysteine proteases coordinate the highly disparate processes of apoptosis and inflammation. However, although hundreds of substrates for the apoptosis effector caspases (caspase-3 and caspase-7) have been identified, only two confirmed substrates for the key inflammatory protease (caspase-1) are known. Whether this reflects intrinsic differences in the substrate specificity of inflammatory versus apoptotic caspases or their relative abundance in vivo is unknown. To address this issue, we have compared the specificity of caspases-1, -3, and -7 toward peptide and protein substrates. Contrary to expectation, caspase-1 displayed concentration-dependent promiscuity toward a variety of substrates, suggesting that caspase-1 specificity is maintained by restricting its abundance. Although endogenous concentrations of caspase-1 were found to be similar to caspase-3, processed caspase-1 was found to be much more labile, with a half-life of ~9 min. This contrasted sharply with the active forms of caspase-3 and caspase-7, which exhibited half-lives of 8 and 11 h, respectively. We propose that the high degree of substrate specificity displayed by caspase-1 is maintained through rapid spontaneous inactivation of this protease.

Human and murine granzyme B exhibit divergent substrate preferences.

The cytotoxic lymphocyte protease granzyme B (GzmB) can promote apoptosis through direct processing and activation of members of the caspase family. GzmB can also cleave the BH3-only protein, BID, to promote caspase-independent mitochondrial permeabilization. Although human and mouse forms of GzmB exhibit extensive homology, these proteases diverge at residues predicted to influence substrate binding. We show that human and mouse GzmB exhibit radical differences in their ability to cleave BID, as well as several other key substrates, such as ICAD and caspase-8. Moreover, pharmacological inhibition of caspases clonogenically rescued human and mouse target cells from apoptosis initiated by mouse GzmB, but failed to do so in response to human GzmB. These data demonstrate that human and murine GzmB are distinct enzymes with different substrate preferences. Our observations also illustrate how subtle differences in enzyme structure can radically affect substrate selection.

Executioner caspase-3 and caspase-7 are functionally distinct proteases.

Members of the caspase family of cysteine proteases play central roles in coordinating the stereotypical events that occur during apoptosis. Because the major executioner caspases, caspase-3 and caspase-7, exhibit almost indistinguishable activity toward certain synthetic peptide substrates, this has led to the widespread view that these proteases occupy functionally redundant roles within the cell death machinery. However, the distinct phenotypes of mice deficient in either of these caspases, as well as mice deficient in both, is at odds with this view. These distinct phenotypes could be related to differences in the relative expression levels of caspase-3 and caspase-7 in vivo, or due to more fundamental differences between these proteases in terms of their ability to cleave natural substrates. Here we show that caspase-3 and caspase-7 exhibit differential activity toward multiple substrate proteins, including Bid, XIAP, gelsolin, caspase-6, and cochaperone p23. Caspase-3 was found to be generally more promiscuous than caspase-7 and appears to be the major executioner caspase during the demolition phase of apoptosis. Our observations provide a molecular basis for the different phenotypes seen in mice lacking either caspase and indicate that these proteases occupy nonredundant roles within the cell death machinery.

Testing Measurement Properties of the Norwegian Version of Electronic Health Literacy Scale (eHEALS) in a Group of Day Surgery Patients.

BACKGROUND AND AIM: In order to assess patients' ability to search, understand, and benefit from Internet-based information, several screening tools have been developed. One of these tools, which has been widely used, is the eHealth Literacy Scale (eHEALS). The aim of this study was to examine the measurement properties of the Norwegian version of the eHEALS, as it was used in a group of patients undergoing day surgery. METHODS: A cross-sectional survey study was conducted among 119 patients scheduled for day surgical treatment in a Norwegian hospital. The questionnaire included the screening tool eHEALS, which contains 8 items for assessing a person's information awareness skills, information seeking skills, and skills to evaluate and act based on the information. Cronbach's alpha coefficients and item-total correlations were assessed for estimating reliability of the eHEALS. Exploratory factor analysis with Oblimin rotation was used for assessing the validity of the scale. Eigenvalue was set to 1.0. RESULTS: A Cronbach's alpha coefficient of 0.89 for the total scale, values >0.82 for Alpha if Item Deleted, and moderate to high item-total correlations supported the homogeneity and internal consistency of the scale. A two-component solution explained a total of 74.8% of the variance, with the first component explaining 59.53% of the variance in the scale and included the items reflecting information awareness and seeking. The second component explained 15.23% of the variance, including items reflecting the ability to evaluate and act. CONCLUSION: The reliability of the Norwegian version of eHEALS, used in a group of patients undergoing day surgery, was good. The internal structure, with two distinct factors, is in line with several previous studies. The eHEALS appears to be an appropriate tool for assessing eHealth literacy among this patient group.

Proteomic and functional analysis identifies galectin-1 as a novel regulatory component of the cytotoxic granule machinery.

Secretory granules released by cytotoxic T lymphocytes (CTLs) are powerful weapons against intracellular microbes and tumor cells. Despite significant progress, there is still limited information on the molecular mechanisms implicated in target-driven degranulation, effector cell survival and composition and structure of the lytic granules. Here, using a proteomic approach we identified a panel of putative cytotoxic granule proteins, including some already known granule constituents and novel proteins that contribute to regulate the CTL lytic machinery. Particularly, we identified galectin-1 (Gal1), an endogenous immune regulatory lectin, as an integral component of the secretory granule machinery and unveil the unexpected function of this lectin in regulating CTL killing activity. Mechanistic studies revealed the ability of Gal1 to control the non-secretory lytic pathway by influencing Fas-Fas ligand interactions. This study offers new insights on the composition of the cytotoxic granule machinery, highlighting the dynamic cross talk between secretory and non-secretory pathways in controlling CTL lytic function.

P73 status in B-cell chronic lymphocytic leukaemia.

B-cell chronic lymphocytic leukemia is a heterogenous disease with disturbed apoptosis in which the precise molecular defects leading to this pathogenesis are still unclear. The p73 gene (a p53 homologue) encodes 2 proteins with opposing functions. TAp73 induces cell cycle arrest and apoptosis, whilst the oncogenic deltaNp73 inhibits both TAp73 and p53 induced apoptosis. Microsatellite analysis was performed to investigate the p73 gene locus in B-CLL. Moreover, we investigated the expression of the TAp73 and deltaNp73 variant by measuring the mRNA transcripts in 51 B-CLL patients by real-time RT-PCR. And in addition, protein expression was analyzed by Western blotting technique in 20 B-CLL patients. There was no evidence of clonal loss of heterozygosity at 1p36, the p73 gene locus in B-CLL patients. The real time RT-PCR analysis showed that the expression of both p73 gene variants was much higher in leukemic cells compared to controls. In 17/20 (85%) patients deltaNp73 and TAp73 protein were present. The observed increase of expression of the antiapoptotic deltaNp73 variant in neoplastic cells may lead to a functional p53 inactivation. This mechanism might be relevant in malignancies with an intact p53 gene but disturbed apoptosis mechanisms such as in B-CLL.

Sensitive and rapid detection of ganciclovir resistance by PCR based MALDI-TOF analysis.

BACKGROUND: Cytomegalovirus (CMV) infection is associated with significant morbidity and mortality in transplant recipients. Resistance against ganciclovir is increasingly observed. According to current guidelines, direct drug resistance testing is not always performed due to high costs and work effort, even when resistance is suspected. OBJECTIVES: To develop a more sensitive, easy applicable and cost-effective assay as proof of concept for direct drug resistance testing in CMV surveillance of post-transplant patients. STUDY DESIGN: Five consecutive plasma samples from a heart transplant patient with a primary CMV infection were analyzed by quantitative real-time polymerase chain reaction (rtPCR) as a surrogate marker for therapy failure, and by direct drug resistance detection assays such as Sanger sequencing and the novel primer extension (PEX) reaction matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) based method. RESULTS: This report demonstrates that PEX reaction followed by MALDI-TOF analysis detects the A594V mutation, encoding ganciclovir resistance, ten days earlier compared to Sanger sequencing and more than 30 days prior to an increase in viral load. CONCLUSION: The greatly increased sensitivity and rapid turnaround-time combined with easy handling and moderate costs indicate that this procedure could make a major contribution to improve transplantation outcomes.

Nucleophosmin is cleaved and inactivated by the cytotoxic granule protease granzyme M during natural killer cell-mediated killing.

Natural killer (NK) cells kill virus-infected or transformed target cells by delivering cytotoxic proteases called granzymes to the target cell cytosol. One of these proteases, granzyme M, is specifically expressed in NK cells and is thought to instigate a form of cell death distinct from that mediated by granzyme A or granzyme B. However, the mechanism of granzyme M-induced cell death is unclear at present, and few substrates for this granzyme have been reported to date. Here we show that the abundant nucleolar phosphoprotein, nucleophosmin (NPM), is cleaved and inactivated by granzyme M. NPM is essential for cell viability as RNA interference-mediated ablation of NPM expression in human cells resulted in spontaneous apoptosis. Significantly, overexpression of wild-type NPM rescued cells treated with NPM small interference RNA, whereas overexpression of the granzyme M-cleaved form of NPM did not. Because NPM is essential for cell viability, these data suggest that targeting of NPM by granzyme M may contribute to tumor cell eradication by abolishing NPM function.

Analysis of apoptosis in cell-free systems.

Cell-free systems have been instrumental in the identification of several important components of the cell death machinery such as cytochrome c, APAF-1, ICAD/CAD (DFF45/DFF40) and Smac/Diablo. Such systems have also proved invaluable for the detailed analysis of caspase activation mechanisms, caspase activation cascades, proteolysis of caspase substrates, apoptosis-associated chromatin condensation and internucleosomal DNA fragmentation. Here, we describe a cell-free system that we have used routinely in our laboratory for the analysis of caspase activation and associated events. Caspase activation in this system can be triggered either through assembly of the APAF-1 apoptosome by addition of cytochrome c/dATP, or alternatively, by addition of the cytotoxic lymphocyte protease, granzyme B. In both cases, the order of caspase activation events has been established and the relative importance of individual caspases to apoptosis-associated nuclear events, as well as substrate proteolysis, is known. Cell-free systems are therefore very useful for screening potential caspase-inhibitory compounds or other agents that may positively or negatively affect caspase-dependent events in apoptosis.

Two-dimensional gel-based analysis of the demolition phase of apoptosis.

Apoptosis is coordinated by members of the caspase family of aspartic acid-specific proteases. To date, over 400 substrates for the apoptosis-associated caspases have been reported and there are likely to be hundreds more yet to be discovered. Global approaches toward identifying proteins cleaved by caspases during apoptosis are now possible and give a more complete perspective on the alterations to the proteome that occur during this complex process. This chapter outlines methods that have been used successfully to visualize the demolition phase of apoptosis by two-dimensional gel electrophoresis coupled with mass spectrometry. It discusses techniques used to generate cell-free extracts from human cells and details how these extracts can be used to activate caspases. The analysis of these extracts by two-dimensional gel electrophoresis is then described, followed by methods used to identify changes to the proteome during the demolition phase of apoptosis.