Adeno-associated virus-mediated IL-10 gene therapy inhibits diabetes recurrence in syngeneic islet cell transplantation of NOD mice

Islet transplantation represents a potential cure for type 1 diabetes, yet persistent autoimmune and allogeneic immunities currently limit its clinical efficacy. For alleviating the autoimmune destruction of transplanted islets, newly diagnosed NOD mice were provided a single intramuscular injection of recombinant adeno-associated viral vector encoding murine IL-10 (rAAV-IL-10) 4 weeks before renal capsule delivery of 650 syngeneic islets. A dose-dependent protection of islet grafts was observed. Sixty percent (3 of 5) of NOD mice that received a transduction of a high-dose (4 x 10(9) infectious units) rAAV-IL-10 remained normoglycemic for at least 117 days, whereas diabetes recurred within 17 days in mice that received a low-dose rAAV-IL-10 (4 x 10(8) infectious units; 5 of 5) as well as in all of the control mice (5 of 5 untreated and 4 of 4 rAAV-green fluorescent protein-transduced). Serum IL-10 levels positively correlated with prolonged graft survival and were negatively associated with the intensity of autoimmunity. The mechanism of rAAV-IL-10 protection involved a reduction of lymphocytic infiltration as well as induction of antioxidant enzymes manganese superoxide dismutase and heme oxygenase 1 in islet grafts. These studies support the utility of immunoregulatory cytokine gene therapy delivered by rAAV for preventing autoimmune disease recurrence in transplant-based therapies for type 1 diabetes.

Pre-operative screening: criteria for referring to anaesthetists

Nurses assess patients pre-operatively using screening questionnaires and locally-developed protocols. Our objectives were to determine which questions might identify patients who should be seen by an anaesthetist before the day of surgery. A review of the literature and a preliminary questionnaire to establish questions to be tested was followed by a modified, two-round Delphi questionnaire to determine the level of agreement by anaesthetists. There was agreement for referring patients who gave a positive response to questions that query: restricted exercise tolerance; previous anaesthetic problems; family history of anaesthetic problem; pathology affecting neck movement; angina; arrhythmia; heart failure; asthma; epilepsy; insulin-dependent diabetes mellitus; liver disease and unspecified kidney disease. There was equivocal agreement on questions that report a myocardial infarction over one year ago, cerebrovascular accident, non insulin-dependent diabetes mellitus and thyroid disease. Nurses should use these criteria during pre-operative assessment to decide the timing of evaluation by an anaesthetist.

T cells require TRAIL for optimal graft-versus-tumor activity

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a member of the TNF superfamily that exhibits specific tumoricidal activity against a variety of tumors. It is expressed on different cells of the immune system and plays a role in natural killer cell-mediated tumor surveillance. In allogeneic hematopoietic-cell transplantation, the reactivity of the donor T cell against malignant cells is essential for the graft-versus-tumor (GVT) effect. Cytolytic activity of T cells is primarily mediated through the Fas-Fas ligand and perforin-granzyme pathways. However, T cells deficient for both Fas ligand and perforin can still exert GVT activity in vivo in mouse models. To uncover a potential role for TRAIL in donor T cell-mediated GVT activity, we compared donor T cells from TRAIL-deficient and wild-type mice in clinically relevant mouse bone-marrow transplantation models. We found that alloreactive T cells can express TRAIL, but the absence of TRAIL had no effect on their proliferative and cytokine response to alloantigens. TRAIL-deficient T cells showed significantly lower GVT activity than did TRAIL-expressing T cells, but no important differences in graft-versus-host disease, a major complication of allogeneic hematopoietic cell transplantation, were observed. These data suggest that strategies to enhance TRAIL-mediated GVT activity could decrease relapse rates of malignancies after hematopoietic cell transplantation without exacerbation of graft-versus-host disease.

Combination of interferon alfa-2b and ribavirin in liver transplant recipients with histological recurrent hepatitis C

Recurrent hepatitis C virus (HCV) infection is an important cause of fibrosis and cirrhosis after liver transplantation (LT), with histological recurrence developing in at least 50% of patients within the first year. The aim of this study is to assess the safety and efficacy of interferon alfa-2b plus ribavirin in treating histological recurrent HCV after LT. Since 1998, patients with HCV with significant histological recurrence (fibrosis >/= 3 and/or histological activity index >/= 5) or progressive cholestatic disease after LT were treated with interferon alfa-2b (3 million units subcutaneously three times weekly) plus ribavirin (800 to 1,000 mg/d) for 12 months. Immunosuppression was tapered to cyclosporine/FK506 monotherapy. HCV RNA was assessed at entry, week 24, end of treatment, and 6 months after therapy. The primary end point was loss of HCV RNA 6 months after therapy, whereas the secondary end point was histological response. Fifty-four patients met criteria for treatment and have completed follow-up. Patients were mainly men (71% men; mean age, 51 +/- 5 years) with genotype 1 infection (88%) and high viral load (mean HCV RNA, 38 +/- 9 mEq/mL). Dose modification was required in 72% of patients because of cytopenia or side effects. Intent-to-treat analysis showed that serum HCV RNA was undetectable in 19 patients (35%) week 24, 21 patients (38%) week 48, and 16 patients (30%) at the 6-month follow-up. Paired liver biopsy results (before and within 6 months after treatment) were available for 35 patients. Patients who achieved viral eradication had no significant progression of fibrosis after 1 year of therapy. In summary, combination therapy is a reasonable antiviral option for recurrent HCV infection for established post-LT hepatitis and appears to prevent histological progression of disease if viral eradication is successful.

Radiation pneumonitis in mice: a severe injury model for pneumocyte engraftment from bone marrow

OBJECTIVE

To better understand the process by which pneumocytes can be derived from bone marrow cells, we investigated the in vivo kinetics of such engraftment following lethal irradiation.

METHODS

A cohort of lethally irradiated B6D2F1 female mice received whole bone marrow transplants (BMT) from age-matched male donors and were sacrificed at days 1, 3, 5, and 7 and months 2, 4, and 6 post-BMT (n = 3 for each time point). Additionally, 2 female mice who had received 200 male fluorescence-activated cell sorter (FACS)-sorted CD34(+)lin(-) cells were sacrificed 8 months post-BMT.

RESULTS

Lethal irradiation caused histologic evidence of pneumonitis including alveolar breakdown and hemorrhage beginning at day 3. To identify male-derived pneumocytes, simultaneous fluorescence in situ hybridization (FISH) for Y-chromosome and surfactant B messenger RNA was performed on lung tissue. Y(+) type II pneumocytes were engrafted as early as day 5 posttransplant, and eventually from 2 to 14% of the pneumocytes were donor derived in individual mice. Co-staining for epithelial-specific cytokeratins demonstrated that by 2 months, marrow-derived pneumocytes could comprise entire alveoli, suggesting that type I cells derived from type II pneumocytes.

CONCLUSIONS

We conclude that alveolar lining cells derive from bone marrow cells immediately after acute injury. Also, the CD34(+)lin(-) subpopulation is capable of such pulmonary engraftment.

Adeno-associated virus transduction of islets with interleukin-4 results in impaired metabolic function in syngeneic marginal islet mass transplantation

Previous studies suggest that therapeutic expression of interleukin (IL)-4 by islet cells improves their efficacy in transplantation models directed at reversing type 1 diabetes. We investigated the effects of introducing IL-4 into islets with recombinant adeno-associated virus (rAAV) on the reversal of hyperglycemia in a syngeneic marginal islet mass transplantation model. C57BL/6 islets were mock-transduced or transduced with rAAV expressing murine IL-4 (rAAV-IL-4) or rAAV expressing green fluorescent protein (rAAV-GFP) before transplantation of a marginal mass into diabetic mice. Normoglycemia was achieved in only 1/7 mice receiving rAAV-IL-4 transduced islets in comparison to 6/6 mock-transduced and 4/6 rAAV-GFP transduced animals. The failure of IL-4 expressing islets was not associated with cellular toxicity of rAAV or impairment of glucose-stimulated insulin release in vitro. Islet expression of IL-4 led to impaired metabolic function in mice receiving a marginal mass of syngeneic islets.

Utilization of acidophil bodies in the diagnosis of recurrent hepatitis C infection after orthotopic liver transplantation

BACKGROUND

The distinction between acute rejection and early recurrent hepatitis C infection (RHCV) in the setting of orthotopic liver transplantation is often difficult. In liver biopsies acidophil bodies and lobular hepatitis are used to suggest a diagnosis of RHCV over rejection, however, the reliability of this practice has not been established. Because portal tract changes in RHCV and rejection often overlap, we sought to determine whether the degree of hepatocyte acidophil body formation seen on liver biopsies could be used to distinguish between these two conditions.

METHODS

Quantification of acidophil bodies was performed on liver biopsies in orthotopic liver transplant patients with RHCV (n = 10), non-hepatitis C orthotopic liver transplant patients with uncomplicated rejection episodes (n = 10) and non-transplant patients with chronic hepatitis C infection (n = 10). Hematoxylin and Eosin stained slides from all three groups were randomized and tissue segments 1.0 cm in length and of variable width (0.04-0.13 cm) were examined at 200x magnification in a blinded fashion by two pathologists in order to quantify the number of acidophil bodies/cm(2). Lobular chronic inflammation was also graded on a 0-3+ scale.

RESULTS

Liver biopsies taken at the onset of RHCV exhibited 606 +/- 101 acidophil bodies/cm(2) (mean +/- standard error of mean, range 200-1390). These counts were significantly greater (P =.0061, paired 2-tailed t-test) than the 241 +/- 53 acidophil bodies/cm(2) (range 80-514) for acute rejection, and the 194 +/- 21 acidophil bodies/cm(2) (range 100-333) for non-liver transplant chronic hepatitis C infection (P =.0013). No difference in lobular inflammation between index RHCV and rejection biopsies was detected.

CONCLUSIONS

Although there is overlap, on average there are twice as many acidophil bodies in the initial stage of RHCV when compared with acute rejection (average of 55 per linear cm in RHCV versus 21 per linear cm for rejection). Lobular inflammation was not a reliable indicator of the initial onset of RHCV.

Hepatic oval (stem) cell expression of endothelial differentiation gene receptors for lysophosphatidic acid in mouse chronic liver injury

Growth factor lysophosphatidic acid (LPA) regulates cell proliferation and differentiation and increases motility and survival in several cell types, mostly via G-protein-coupled receptors encoded by endothelial differentiation genes (EDG). We show herein that hepatic oval (stem) cell proliferation, induced by 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) in a mouse model of chronic liver injury, was associated with the expression of LPA1, LPA2, and LPA3 receptor subtypes; only LPA1 receptor protein was detectable in normal liver by western blot. In the injured liver, enhanced LPA1 receptor was identified predominantly in oval cells along the portal tract, proliferating ductular epithelial cells, and small cells, which were located in the nearby parenchyma and formed clusters. Interestingly, the LPA1 receptor was co-expressed in DDC-treated livers with the stem cell antigen SCA-1, suggesting that this receptor may be associated with bone marrow-derived progenitors. All three receptors for LPA were detected mostly in small cells in the vicinity of the portal tract, and co-localized with the A6 antigen, a marker of ductular oval cells. In addition, hepatic levels of endogenous LPA were significantly higher in DDC-fed mice compared to normal animals. We propose that the expression of diverse LPA receptors may be a necessary part of the mechanism responsible for activation of oval cells during liver injury. As a result, LPA and its analogs may represent critical endogenous mediators, which regulate survival, increase motility, and modulate proliferation and differentiation of hepatocyte progenitors in regenerating liver.

Development of the intrahepatic biliary tree

The liver develops from two anlages: the hepatic diverticulum, which buds off the ventral side of the foregut, and the septum transversum, which is the mesenchymal plate that partially separates the embryonic thoracic and abdominal cavities. The endodermal cells of the hepatic diverticulum invade the septum transversum, forming sheets and cords of hepatoblasts arrayed along the sinusoidal vascular channels derived from the vitelline veins emanating from the yolk sac. The vitelline veins fuse to form the portal vein, which ramifies as tributaries within the liver along mesenchymal channels termed portal tracts. Those hepatoblasts immediately adjacent to the mesenchyme of the portal tracts differentiate into a ductal plate, a single circumferential layer of biliary epithelial cells. Mesenchymal cells interpose between the ductal plate and the remaining parenchymal hepatoblasts, which differentiate into hepatocytes. By week 7 the ductal plate begins to reduplicate, forming a double layer of cells around the portal tract. Lumena form between the two cell layers of the ductal plate, forming peripheral biliary tubular structures. These peripheral tubules remodel and, with continued proliferation of the mesenchyme, by the 11th week begin to become more centrally located within portal tracts as terminal bile ducts with a circular cross-section. The remaining ductal plate resorbs, leaving behind only tethers of bile ductules connecting the terminal bile ducts to the parenchyma. Abutting and within the parenchyma are the canals of Hering, ductular structures half-lined by hepatocytes and half-lined by biliary epithelial cells. Maturation of the intrahepatic biliary tree to the mature tubular treelike architecture occurs from the hilum of the liver outward, beginning around the 11th week of gestation and continuing past birth for several months. The architecture of maturation is the same regardless of gestational age or radial location in the liver. Importantly, the immature intrahepatic biliary system maintains patency and continuity with the extrahepatic biliary tree throughout gestation, with no evidence of a solid phase of development. Thus, from the earliest time of hepatocellular bile formation beginning around the 12th week, there is a patent passage to the alimentary canal.

EDG receptors and hepatic pathophysiology of LPA and S1P: EDG-ology of liver injury

The biological roles of phospholipid growth factors lysophosphatidic acid (LPA) and sphingosine-1-phosphate (S1P) have been broadly investigated. The cellular effects of LPA and S1P are mediated predominantly via endothelial differentiation gene (EDG) receptors. Yet, the biological significance of LPA, S1P and their EDG receptors in cells of the liver remains unclear. Recent data demonstrate the presence of EDG2 and EDG4 mRNA for LPA receptor in a murine hepatocyte cell line transformed with human TGF-alpha, and in primary mouse hepatocytes. EDG2 receptor protein is expressed in mouse liver, where it appears to be located in nonparenchymal cells. Moreover, we have obtained data suggesting that proliferation of small hepatocyte-progenitors and stem (oval) cells during liver injury is associated with the expression of EDG2 and EDG4 receptors. LPA, and possibly S1P, appear to be essential factors that control proliferation and motility of hepatic stellate cells (HSC) and hepatoma cells. It is proposed that LPA, S1P and their respective EDG receptors play important roles in pathophysiology of chronic liver injury and fibrogenesis. The underlying mechanisms recruited by LPA and S1P in pathogenesis of liver injury remain to be investigated.

Enhancement of survival by LPA via Erk1/Erk2 and PI 3-kinase/Akt pathways in a murine hepatocyte cell line

First published September 5, 2001; 10.1152/ajpcell.00077.2001.-Protective mechanisms for lysophosphatidic acid (LPA) against cell death caused by Clostridium difficile toxin, or tumor necrosis factor-alpha (TNF-alpha) plus D-galactosamine, were investigated in a murine hepatocyte cell line AML12 expressing Edg2 LPA receptor. In these models of hepatocellular injury, LPA prevented hepatocyte damage, suppressed apoptosis, and enhanced cell survival in a dose-dependent fashion. The protective effects of LPA were abolished by wortmannin and LY-294002, specific inhibitors of phosphatidylinositol 3-phosphate kinase (PI 3-kinase), and by PD-98059 and U-0126, inhibitors of MEK1/MEK2. In nontreated hepatocytes, LPA elicited a gradual and sustained increase in phosphorylation of Erk1/Erk2 over 180 min of stimulation and downstream phosphorylation of p90RSK and transcription factor Elk-1. In C. difficile toxin-treated cells, LPA-induced phosphorylation of Erk1/Erk2 was rapid but transient, while p90RSK and Elk-1 phosphorylation did not change significantly. LPA stimulated phosphorylation of Akt in a time-dependent manner in both intact and toxin-treated AML12 hepatocytes. Wortmannin and LY-294002 abolished phosphorylation of Akt, further supporting activation of PI 3-kinase/Akt as a signaling pathway, which mediates hepatocyte protection by LPA. Taken together, these results demonstrate that LPA prevents cell apoptosis induced by C. difficile toxin and TNF-alpha/D-galactosamine in the AML12 murine hepatocyte cell line. Cell protection by LPA involves activation of the mitogen-activated protein kinase Erk1/Erk2 cascade and PI 3-kinase-dependent phosphorylation of Akt.

An adenoviral system for tetracycline-regulated TGF-beta expression mediates a reversible cell cycle arrest

The ability to regulate the proliferation of normal cells in a reversible manner would be a useful adjunct to some clinical therapies. including many types of cancer chemotherapy and surgery for periodontal regeneration. While the application of recombinant growth factors and cytokines to target cells is a logical approach to regulate cell proliferation, the high turnover rates of these peptide factors often make this approach impractical. Recombinant adenoviral vectors can be used to direct the expression of transgene products such as growth factors in many cell types in vitro and in vivo. We have adapted the tetracycline-regulated expression system to allow regulated transforming growth factor (TGF)-beta1 expression using recombinant adenovirus. We demonstrate that infection with a recombinant TGF-beta-encoding virus system in primary human oral keratinocytes and in a lung epithelial cell line is sufficient to allow a cell cycle arrest that is reversible upon tetracycline addition. This inhibition is efficient even after the infection of a minority of cells in a population. These results highlight the possibility of using low level infection with recombinant adenovirus to cause short-term blocks on cell proliferation.

Adeno-associated virus vector-mediated IL-10 gene delivery prevents type 1 diabetes in NOD mice

The development of spontaneous autoimmune diabetes in nonobese diabetic (NOD) mice provides for their use as a model of human type 1 diabetes. To test the feasibility of muscle-directed gene therapy to prevent type 1 diabetes, we developed recombinant adeno-associated virus (rAAV) vectors containing murine cDNAs for immunomodulatory cytokines IL-4 or IL-10. Skeletal muscle transduction of female NOD mice with IL-10, but not IL-4, completely abrogated diabetes. rAAV-IL-10 transduction attenuated the production of insulin autoantibodies, quantitatively reduced pancreatic insulitis, maintained islet insulin content, and altered splenocyte cytokine responses to mitogenic stimulation. The beneficial effects were host specific, as adoptive transfer of splenocytes from rAAV IL-10-treated animals rapidly imparted diabetes in naive hosts, and the cells contained no protective immunomodulatory capacity, as defined through adoptive cotransfer analyses. These results indicate the utility for rAAV, a vector with advantages for therapeutic gene delivery, to transfer immunoregulatory cytokines capable of preventing type 1 diabetes. In addition, these studies provide foundational support for the concept of using immunoregulatory agents delivered by rAAV to modulate a variety of disorders associated with deleterious immune responses, including allergic reactions, transplantation rejection, immunodeficiencies, and autoimmune disorders.

Observed incidence of tumorigenesis in long-term rodent studies of rAAV vectors

Gene therapy using recombinant adeno-associated virus vectors (rAAV) is generally considered safe. During the course of a study designed to determine the long-term efficacy of rAAV-mediated gene therapy initiated in newborn mice with the lysosomal storage disease, mucopolysaccharidosis type VII (MPSVII), a significant incidence of hepatocellular carcinomas and angiosarcomas was discovered. A hepatocellular carcinoma was first detected in a 35-week-old mouse and by 72 weeks of age, three out of five rAAV-treated MPSVII mice had similar lesions. These types of tumors had not been seen previously in long-term studies of MPSVII mice using recombinant enzyme or bone marrow transplantation. In an attempt to ascertain whether mouse strain or GUSB expression confers susceptibility to tumor formation, we histopathologically examined untreated normal mice of the same strain, untreated MPSVII mice, and normal mice overexpressing human GUSB for the presence of tumors and increased hepatocyte replication. The results of these studies do not indicate that MPSVII mice or mice overexpressing human GUSB are susceptible to tumor formation; however, the number of animals examined is too small to draw definitive conclusions. Results from quantitative PCR performed on the tumor samples suggest that the tumors are probably not caused by an insertional mutagenesis event followed by the clonal expansion of a transformed cell. In a separate study, a relatively large group of mice injected with varying doses and types of rAAV vectors had no evidence of hepatic or vascular tumors. Although the mechanism of tumor formation is currently unknown, the tumorigenic potential of rAAV vectors must be rigorously determined in long-term in vivo studies.

Stable therapeutic serum levels of human alpha-1 antitrypsin (AAT) after portal vein injection of recombinant adeno-associated virus (rAAV) vectors

Previous work from our group showed that recombinant adeno-associated virus (rAAV) vectors mediated long-term secretion of therapeutic serum levels of human alpha-1 antitrypsin (hAAT) after a single injection in murine muscle. We hypothesized that hepatocyte transduction could be even more efficient, since these cells represent the natural site of AAT production and secretion. To test this hypothesis, rAAV vectors containing the hAAT cDNA driven by either the human elongation factor 1 alpha promoter, the human cytomegalovirus immediate-early promoter (CMV), or the CMV-chicken beta actin hybrid (CB) promoter were injected into the portal or tail veins of adult C57Bl/6 mice. Potentially therapeutic serum levels of hAAT (600 microg/ml) were achieved after portal vein injection of doses of 4 x 10(9) infectious units (IU), a 10-fold lower dose than that required for similar levels of expression via the i.m. route. Serum levels greater than 1 mg/ml were achieved at doses of 3 x 10(10) IU. Southern blotting of liver DNA revealed the presence of circular episomal vector genomes. Immunostaining showed that transgene expression was scattered throughout the liver parenchyma. Similar results were obtained with a rAAV-CB-green fluorescent protein (GFP) vector. There was no evidence of hepatic toxicity. These data indicate that liver-directed rAAV-based gene therapy is effective in the murine model, and hence might be feasible for treatment of human AAT deficiency.

LPS antagonism reduces graft-versus-host disease and preserves graft-versus-leukemia activity after experimental bone marrow transplantation

Acute graft-versus-host disease (GVHD) and leukemic relapse remain the two major obstacles to successful outcomes after allogeneic bone marrow transplantation (BMT). Recent studies have demonstrated that the loss of gastrointestinal tract integrity, and specifically the translocation of LPS into the systemic circulation, is critical to the induction of cytokine dysregulation that contributes to GVHD. Using a mouse BMT model, we studied the effects of direct LPS antagonism on GVHD severity and graft-versus-leukemia (GVL) activity. Administration of B975, a synthetic lipid-A analogue from day 0 to day +6, reduced serum TNF-alpha levels, decreased intestinal histopathology, and resulted in significantly improved survival and a reduction in clinical GVHD, compared with control-treated animals. Importantly, B975 had no effect on donor T cell responses to host antigens in vivo or in vitro. When mice received lethal doses of P815 tumor cells at the time of BMT, administration of B975 did not impair GVL activity and resulted in significantly improved leukemia-free survival. These findings reveal a critical role for LPS in the early inflammatory events contributing to GVHD and suggest that a new class of pharmacologic agents, LPS antagonists, may help to prevent GVHD while preserving T cell responses to host antigens and GVL activity.

Negotiated safety and other agreements between men in relationships: risk practice redefined

This study examines patterns of agreement, knowledge and practice which can prevent or facilitate HIV transmission among men who are in regular ('primary') male-to-male relationships. Data are from a national volunteer phone-in survey of homosexually-active men in Australia. A sub-sample of 1070 men from a larger sample (n=3039) were found to have one or more regular partners for longer than 6 months. Self-reported HIV serostatus of survey participant and his regular partner, type of agreement regarding anal intercourse both within and outside the regular relationship, and engaging in unprotected anal intercourse with regular and with casual partners were examined. Risk practice was defined as unprotected anal intercourse with a regular partner of different or unknown serostatus and/or unprotected anal intercourse with a casual partner. Agreements were classified as: negotiated safety (28.8%); no unprotected anal intercourse (33.6%); unsafe (10.6%) and no agreement (17.0%). Risk practice was reported by 17.8% of the men. Type of agreement was found to be the strongest predictor of risk practice. Negotiated safety agreements were common, and were kept on the whole. Men with unsafe agreements, although only a small proportion of men in relationships, had high levels of risk practice.

Role of myosin-II phosphorylation in V12Cdc42-mediated disruption of Drosophila cellularization

Microinjection of constitutively active Cdc42 (V12Cdc42) disrupts the actomyosin cytoskeleton during cellularization (Crawford et al., Dev. Biol., 204, 151-164 (1998)). The p21-activated kinase (PAK) family of Ser/Thr kinases are effectors of GTP-bound forms of the small GTPases, Cdc42 and Rac. Drosophila PAK, which colocalizes with actin and myosin-II during cellularization, concentrates at sites of V12Cdc42-induced actomyosin disruption. In vitro biochemical analyses demonstrate that PAK phosphorylates the regulatory light chain (RLC) of Drosophila nonmuscle myosin-II on Ser21, a site known to activate myosin-II function. Although activated PAK does not disrupt the actomyosin cytoskeleton, it induces increased levels of Ser21 phosphorylated RLC. These findings suggest that increased levels of RLC phosphorylation do not contribute to disruption of the actomyosin hexagonal array.

Hyporesponsiveness of donor cells to lipopolysaccharide stimulation reduces the severity of experimental idiopathic pneumonia syndrome: potential role for a gut-lung axis of inflammation

Idiopathic pneumonia syndrome (IPS) is a major complication of allogeneic bone marrow transplantation (BMT). We have shown that experimental IPS is associated with increased levels of LPS and TNF-alpha in the bronchoalveolar lavage (BAL) fluid. We hypothesized that the deleterious effects of these inflammatory mediators in the lung may be linked to gut injury that develops after BMT. To test this hypothesis, we used mouse strains that differ in their sensitivity to LPS as donors in an experimental BMT model. Lethally irradiated C3FeB6F(1) hosts received BMT from either LPS-sensitive or LPS-resistant donors. Five weeks after BMT, LPS-resistant BMT recipients had significantly less lung injury compared with recipients of LPS-sensitive BMT. This effect was associated with reductions in TNF-alpha secretion (both in vitro and in vivo), BAL fluid LPS levels, and intestinal injury. The relationship between TNF-alpha, gut toxicity, and lung injury was examined further by direct cytokine blockade in vivo; systemic neutralization of TNF-alpha resulted in a significant reduction in gut histopathology, BAL fluid LPS levels, and pulmonary dysfunction compared with control-treated animals. We conclude that donor resistance to endotoxin reduces IPS in this model by decreasing the translocation of LPS across the intestinal border and systemic and pulmonary TNF-alpha production. These data demonstrate a potential etiologic link between gut and lung damage after BMT and suggest that methods that reduce inflammatory responses to LPS, and specifically, those that protect the integrity of the gut mucosa, may be effective in reducing IPS after BMT.

Reduced susceptibility of nonobese diabetic mice to TNF-alpha and D-galactosamine-mediated hepatocellular apoptosis and lethality

Nonobese diabetic (NOD/LtJ or NOD) mice are resistant to doses of LPS and D-galactosamine that uniformly produce lethality in C57BL/6J (B6) mice (p < 0.01). Liver caspase-3-like activity, serum transaminase levels (both p < 0.05), and the numbers of apoptotic liver nuclei were also reduced in NOD compared with B6 mice treated with LPS (100 ng) and D-galactosamine (8 mg). NOD mice were also at least 100-fold more resistant to recombinant human TNF-alpha and D-galactosamine treatment than B6 mice (p < 0.001). Binding of recombinant human TNF-alpha to splenocytes from NOD mice was similar to that seen in B6 mice, suggesting that the defect in responsiveness was not due to an inability of recombinant human TNF-alpha to bind the NOD TNF type 1 (p55) receptor. Because the TNF type 1 (p55) receptor shares a common signaling pathway with Fas (CD95), NOD and B6 mice were treated with the Fas agonist antibody, Jo-2. Surprisingly, NOD mice were as sensitive as B6 mice to Fas-induced lethality and hepatic injury. In addition, primary hepatocytes isolated from NOD mice and cultured in vitro in the presence of D-galactosamine with or without TNF-alpha were found to be resistant to apoptosis and cytotoxicity when compared with B6 mice. In contrast, Jo-2 treatment produced similar increases in caspase-3 activity and cytotoxicity in primary hepatocytes from NOD and B6 mice. The resistance to LPS- and TNF-alpha-mediated lethality and hepatic injury in D-galactosamine-sensitized NOD mice is apparently due to a post-TNFR binding defect, and independent of signaling pathways shared with Fas.