Amit D. Tevar

Bortezomib provides effective therapy for antibody- and cell-mediated acute rejection.

Background. Current antihumoral therapies in transplantation and autoimmune disease do not target the mature antibody-producing plasma cell. Bortezomib is a first in class proteosomal inhibitor, that is Food and Drug Administration approved, for the treatment of plasma cell-derived tumors that is multiple myeloma. We report the first clinical experience with plasma cell-targeted therapy (bortezomib) as an antirejection strategy. Methods. Eight episodes of mixed antibody-mediated rejection (AMR) and acute cellular rejection (ACR) in six transplant recipients were treated with bortezomib at labeled dosing. Monitoring included serial donor-specific antihuman leukocyte antigen antibody (DSA) levels and repeated allograft biopsies. Results. Six kidney transplant patients received bortezomib for AMR and concomitant ACR. In each case, bortezomib therapy provided (1) prompt rejection reversal, (2) marked and prolonged reductions in DSA levels, (3) improved renal allograft function, and (4) suppression of recurrent rejection for at least 5 months. Moreover, immunodominant DSA (iDSA) (i.e., the antidonor human leukocyte antigen antibody with the highest levels) levels were decreased by more than 50% within 14 days and remained substantially suppressed for up to 5 months. One or more additional DSA were present at lower concentrations (non-iDSA) in each patient and were also reduced to nondetectable levels. Bortezomib-related toxicities (gastrointestinal toxicity, thrombocytopenia, and paresthesias) were all transient. Conclusions. Bortezomib therapy: (1) provides effective treatment of AMR and ACR with minimal toxicity and (2) provides sustained reduction in iDSA and non-iDSA levels. Bortezomib represents the first effective antihumoral therapy with activity in humans that targets plasma cells.

Reducing De Novo Donor‐Specific Antibody Levels during Acute Rejection Diminishes Renal Allograft Loss

The effect of de novo DSA detected at the time of acute cellular rejection (ACR) and the response of DSA levels to rejection therapy on renal allograft survival were analyzed. Kidney transplant patients with acute rejection underwent DSA testing at rejection diagnosis with DSA levels quantified using Luminex single‐antigen beads. Fifty‐two patients experienced acute rejection with 16 (31%) testing positive for de novo DSA. Median follow‐up was 27.0 ± 17.4 months postacute rejection. Univariate analysis of factors influencing allograft survival demonstrated significance for African American race, DGF, cytotoxic PRA >20% (current) and/or >50% (peak), de novo DSA, C4d and repeat transplantation. Multivariate analysis showed only de novo DSA (6.6‐fold increased allograft loss risk, p = 0.017) to be significant. Four‐year allograft survival was higher with ACR (without DSA) (100%) than mixed acute rejection (ACR with DSA/C4d) (65%) or antibody‐mediated rejection (35%) (p < 0.001). Patients with >50% reduction in DSA within 14 days experienced higher allograft survival (p = 0.039). De novo DSAs detected at rejection are associated with reduced allograft survival, but prompt DSA reduction was associated with improved allograft survival. DSA should be considered a potential new end point for rejection therapy.

Early and Late Acute Antibody-Mediated Rejection Differ Immunologically and in Response to Proteasome Inhibition

Background. The efficacy of plasma cell targeted therapies for antibody-mediated rejection (AMR) has not been defined in detail. The purpose of this study was to compare early and late acute AMR in terms of immunologic characteristics and responses with proteasome inhibitor (PI) therapy. Methods. Renal transplant recipients with acute AMR were treated with PI-based regimens. Early acute AMR was defined as occurring within 6 months posttransplant. Immunodominant donor-specific antibody (iDSA) was defined as the DSA with the highest level. Results. Results are expressed as early or late acute AMR. Thirty AMR episodes (13 early, 17 late) were treated in 12 and 16 patients. Early but not late AMR was associated with presensitization. Late AMR iDSA levels were higher, and specificities were primarily class II (DQ being most frequent). Early AMR patients demonstrated greater reduction in iDSA at 7, 14, and 30 days and at the posttreatment nadir (81.5%+21.2% vs. 51.4%+27.6%; P<0.01). Early AMR patients were more likely to demonstrate histologic resolution/improvement (87.5% vs. 53.8%; P=0.13). Both groups demonstrated significant improvement in renal function. Conclusions. Early and late AMR exhibit distinct immunologic characteristics and respond differently to PI therapy.

De Novo Cancers Arising in Organ Transplant Recipients are Associated With Adverse Outcomes Compared With the General Population

Background. Transplant recipients are at increased risk of malignancy; however, the influence of transplantation on cancer outcomes has not been rigorously defined. The purpose of this study was to examine the influence of transplantation on the outcomes of individual cancers. Methods. De novo nonsmall cell lung cancer, colon cancer, breast cancer, prostate cancer, bladder cancer, renal cell cancer (RCC), and malignant melanoma data in 635 adult (>18 years of age) transplant recipients (from the Israel Penn International Transplant Tumor Registry) were compared with data from 1,282,984 adults in the general population (from the Surveillance, Epidemiology, and End Results database). Results. Compared with the general population, transplant patients were more likely to have early stage (AJCC stage 0–II) RCC, but more advanced (AJCC stage >II) colon cancer, breast cancer, bladder cancer, and malignant melanoma. Compared with the general population, disease-specific survival was worse in the transplant population for colon cancer (all stages), nonsmall cell lung cancer (stage II), breast cancer (stage III), prostate cancer (stage II, III, and IV), bladder cancer (stage III), and RCC (stage IV). Multivariate analyses demonstrated transplantation to be a negative risk factor for survival for each cancer studied, and transplantation and cancer stage at diagnosis to be the most profound negative survival predictors. Conclusions. These analyses indicate that, for several common cancers, transplant patients experience worse outcomes than the general population. The data also suggest that cancers in transplant recipients are more aggressive biologically at the time of diagnosis.

Interleukin-37 reduces liver inflammatory injury via effects on hepatocytes and non-parenchymal cells.

Background and Aim:  The purpose of the present study was to determine the effects of interleukin‐37 (IL‐37) on liver cells and on liver inflammation induced by hepatic ischemia/reperfusion (I/R).

Interleukin-33 is hepatoprotective during liver ischemia/reperfusion in mice.

Interleukin (IL)‐33 is a recently identified member of the IL‐1 family that binds to the receptor, ST2L. In the current study, we sought to determine whether IL‐33 is an important regulator in the hepatic response to ischemia/reperfusion (I/R). Male C57BL/6 mice were subjected to 90 minutes of partial hepatic ischemia, followed by up to 8 hours of reperfusion. Some mice received recombinant IL‐33 (IL‐33) intraperitoneally (IP) before surgery or anti‐ST2 antibody IP at the time of reperfusion. Primary hepatocytes and Kupffer cells were isolated and treated with IL‐33 to assess the effects of IL‐33 on inflammatory cytokine production. Primary hepatocytes were treated with IL‐33 to assess the effects of IL‐33 on mediators of cell survival in hepatocytes. IL‐33 protein expression increased within 4 hours after reperfusion and remained elevated for up to 8 hours. ST2L protein expression was detected in healthy liver and was up‐regulated within 1 hour and peaked at 4 hours after I/R. ST2L was primarily expressed by hepatocytes, with little to no expression by Kupffer cells. IL‐33 significantly reduced hepatocellular injury and liver neutrophil accumulation at 1 and 8 hours after reperfusion. In addition, IL‐33 treatment increased liver activation of nuclear factor kappa light‐chain enhancer of activated B cells (NF‐κB), p38 mitogen‐activated protein kinase (MAPK), cyclin D1, and B‐cell lymphoma 2 (Bcl‐2), but reduced serum levels of CXC chemokines. In vitro experiments demonstrated that IL‐33 significantly reduced hepatocyte cell death as a result of increased NF‐κB activation and Bcl‐2 expression in hepatocytes. Conclusion: The data suggest that IL‐33 is an important endogenous regulator of hepatic I/R injury. It appears that IL‐33 has direct protective effects on hepatocytes, associated with the activation of NF‐κB, p38 MAPK, cyclin D1, and Bcl‐2 that limits liver injury and reduces the stimulus for inflammation. (HEPATOLOGY 2012)

CXC chemokines play a critical role in liver injury, recovery, and regeneration.

BACKGROUND Hepatic ischemia/reperfusion (I/R) injury is a principal consideration of trauma, resectional liver surgery, and transplantation. Despite improvements in supportive care, hepatic I/R injury continues to negatively impact patient outcomes because of significant tissue damage and organ dysfunction. CXC chemokines have been implicated as key mediators in the deleterious inflammatory cascade after hepatic I/R and also as important, beneficial regulators of liver recovery and regeneration. As such, their potential to mediate both beneficial and detrimental effects on hepatocytes makes them a key target for therapy. Herein, we provide a review of the inflammatory mechanisms of hepatic I/R injury, with a focus on the divergent functions of CXC chemokines in this response compared with other liver insults, and offer an explanation of this apparent paradox. DATA SOURCES MEDLINE and PubMed. CONCLUSIONS CXC chemokines are key mediators of both the inflammatory response to hepatic I/R as well as the recovery from this injury. Their contrasting functions in the regeneration of liver mass after an ischemic insult indicates that therapeutic manipulation of these mediator pathways should differ depending on the surgical milieu.

CXC chemokine signaling in the liver: Impact on repair and regeneration

The process of liver repair and regeneration following hepatic injury is complex and relies on a temporally coordinated integration of several key signaling pathways. Pathways activated by members of the CXC family of chemokines play important roles in the mechanisms of liver repair and regeneration through their effects on hepatocytes. However, little is known about the signaling pathways used by CXC chemokine receptors in hepatocytes. Here we review our current understanding of the pathways involved in both CXC chemokine receptor signaling in other cell types, most notably neutrophils, and similar pathways operant during hepatocyte proliferation/liver regeneration to formulate a basis for the function of CXC chemokine receptor signaling in hepatocytes. (HEPATOLOGY 2011;)

CXC chemokine receptor‐1 is expressed by hepatocytes and regulates liver recovery after hepatic ischemia/reperfusion injury

CXC chemokines mediate hepatic inflammation and injury following ischemia/reperfusion (I/R). More recently, signaling through CXC chemokine receptor‐2 (CXCR2) was shown to delay liver recovery and repair after I/R injury. The chemokine receptor CXCR1 shares ligands with CXCR2, yet nothing is known about its potential role in liver pathology. In the present study, we examined the role of CXCR1 in the injury and recovery responses to I/R using a murine model. CXCR1 expression was undetectable in livers of sham‐operated mice. However, after ischemia CXCR1 expression increased 24 hours after reperfusion and was maximal after 96 hours of reperfusion. CXCR1 expression was localized largely to hepatocytes. In order to assess the function of CXCR1, CXCR2−/− mice were treated with the CXCR1/CXCR2 antagonist, repertaxin. Prophylactic treatment with repertaxin had no effect on acute inflammation or liver injury. However, when repertaxin was administered 24 hours postreperfusion there was a significant increase in hepatocellular injury and a delay in recovery compared to control‐treated mice. CXCR1−/− mice also demonstrated delayed recovery and regeneration after I/R when compared to wild‐type mice. In vitro, hepatocytes from CXCR2−/− mice that were stimulated to express CXCR1 showed increased proliferation in response to ligand. Hepatocyte proliferation was decreased in CXCR1−/− mice in vivo. Conclusion: This is the first report to show that CXCR1 expression is induced in hepatocytes after injury. Furthermore, the data suggest that CXCR1 has divergent effects from CXCR2 and appears to facilitate repair and regenerative responses after I/R injury. (HEPATOLOGY 2011)

Receptor activator of nuclear factor‐κB ligand (RANKL) protects against hepatic ischemia/reperfusion injury in mice

The transcription factor nuclear factor kappaB (NF‐κB) plays diverse roles in the acute injury response to hepatic ischemia/reperfusion (I/R). Activation of NF‐κB in Kupffer cells promotes inflammation through cytokine expression, whereas activation in hepatocytes may be cell protective. The interaction of receptor activator of NF‐κB (RANK) and its ligand (RANKL) promotes NF‐κB activation; however, this ligand‐receptor system has not been studied in acute liver injury. In the current study, we sought to determine if RANK and RANKL were important in the hepatic response to I/R. Mice were subjected to partial hepatic ischemia followed by reperfusion. In some experiments, mice received recombinant RANKL or neutralizing antibodies to RANKL 1 hour prior to surgery or at reperfusion to assess the role of RANK/RANKL signaling during I/R injury. RANK was constitutively expressed in the liver and was not altered by I/R. RANK was strongly expressed in hepatocytes and very weakly expressed in Kupffer cells. Serum RANKL concentrations increased after I/R and peaked 4 hours after reperfusion. Serum levels of osteoprotegerin (OPG), a decoy receptor for RANKL, steadily increased over the 8‐hour period of reperfusion. Treatment with RANKL, before ischemia or at reperfusion, increased hepatocyte NF‐κB activation and significantly reduced liver injury. These beneficial effects occurred without any effect on cytokine expression or liver inflammation. Treatment with anti‐RANKL antibodies had no effect on liver I/R injury. Conclusion: During the course of injury, endogenous OPG appears to suppress the effects of RANKL. However, exogenous administration of RANKL, given either prophylactically or postinjury, reduces liver injury in a manner associated with increased hepatocyte NF‐κB activation. The data suggest that RANK/RANKL may be a viable therapeutic target in acute liver injury. (Hepatology 2012)