Requirement of the chemokine receptor CXCR3 for acute allograft rejection

Chemokines provide signals for activation and recruitment of effector cells into sites of inflammation, acting via specific G protein-coupled receptors. However, in vitro data demonstrating the presence of multiple ligands for a given chemokine receptor, and often multiple receptors for a given chemokine, have led to concerns of biologic redundancy. Here we show that acute cardiac allograft rejection is accompanied by progressive intragraft production of the chemokines interferon (IFN)-gamma-inducible protein of 10 kD (IP-10), monokine induced by IFN-gamma (Mig), and IFN-inducible T cell alpha chemoattractant (I-TAC), and by infiltration of activated T cells bearing the corresponding chemokine receptor, CXCR3. We used three in vivo models to demonstrate a role for CXCR3 in the development of transplant rejection. First, CXCR3-deficient (CXCR3(-/)-) mice showed profound resistance to development of acute allograft rejection. Second, CXCR3(-/)- allograft recipients treated with a brief, subtherapeutic course of cyclosporin A maintained their allografts permanently and without evidence of chronic rejection. Third, CXCR(+/+) mice treated with an anti-CXCR3 monoclonal antibody showed prolongation of allograft survival, even if begun after the onset of rejection. Taken in conjunction with our findings of CXCR3 expression in rejecting human cardiac allografts, we conclude that CXCR3 plays a key role in T cell activation, recruitment, and allograft destruction.

Antibiotics prevent liver injury in rats following long-term exposure to ethanol

BACKGROUND/AIMS

Kupffer's cells participate in alcohol-induced liver injury, and endotoxemia is observed in human alcoholics and in a rat model. This study evaluated the effect of reducing bacterial endotoxin production by intestinal sterilization on alcohol-induced liver injury.

METHODS

Male Wistar rats were exposed to ethanol continuously for up to 3 weeks via intragastric feeding. The gut was sterilized with polymyxin B and neomycin.

RESULTS

Fecal culture of stool samples from ethanol-fed rats treated with antibiotics showed virtually no growth of gram-negative bacteria. Endotoxin levels of 80-90 pg/mL in plasma of ethanol-fed rats were reduced to < 25 pg/mL by antibiotics. Antibiotic treatment also completely prevented elevated aspartate aminotransferase levels and significantly reduced the average hepatic pathological score in rats exposed to ethanol. Oxygen tension on the surface of the liver measured in vivo was decreased significantly from control values of 48 +/- 1 to 39 +/- 1 mumol/L in ethanol-treated rats. This hypoxia was prevented by treatment with antibiotics. Moreover, the increase in rates of ethanol elimination due to long-term ethanol treatment was prevented by antibiotic treatment.

CONCLUSIONS

Intestinal sterilization prevented alcohol-induced liver injury in the rat, supporting the idea that hypermetabolism and consequent hypoxia caused by activation of Kupffer's cells by endotoxin is involved in the mechanism.

IL-7 enhances the survival and maintains the size of naive T cells

T cells require continual presence of extrinsic signals from their in vivo microenvironment to maintain viability. T cells removed from these signals and placed in tissue culture atrophied and died in a caspase-independent manner. Atrophy was characterized by smaller cell sizes, delayed mitogenic responses, and decreased glycolytic rate. Bcl-2 expression remained constant in vitro despite ongoing cell death, indicating that endogenous Bcl-2 expression is insufficient to explain the life span and size control of lymphocytes in vivo and that cell-extrinsic signals provided may be required to maintain both cell viability and size in vivo. One such signal, IL-7, was found to maintain both the size and survival of neglected T cells in vitro. IL-7 was not unique, because the common gamma-chain cytokines IL-2, IL-4, and IL-15, as well as the gp130 cytokine IL-6, also promoted both T cell survival and size maintenance. IL-7 did not induce resting T cells to proliferate. Instead, IL-7 stimulated neglected T cells to maintain their metabolic rate at levels comparable to freshly isolated cells. The survival and trophic effects of IL-7 could be separated because IL-7 was able to promote up-regulation of Bcl-2 and maintain cell viability independent of phosphatidylinositol 3-kinase and mammalian target of rapamycin activity but was unable to prevent cellular atrophy when phosphatidylinositol 3-kinase and mammalian target of rapamycin were inhibited. These data demonstrate that T cells require the continuous presence of extrinsic signals not only to survive but also to maintain their size, metabolic activity, and the ability to respond rapidly to mitogenic signals.

Interleukin-6 protects liver against warm ischemia/reperfusion injury and promotes hepatocyte proliferation in the rodent

Interleukin-6 (IL-6) is an acute reactant cytokine with anti-inflammatory properties, which has been found to prevent injury in a model of acute hepatitis in mice through downregulation of tumor necrosis factor alpha (TNF-alpha); to correlate inversely with markers of hepatocellular injury in patients with liver ischemia; and to initiate liver regeneration in mice. In this study, we investigated the role of IL-6 in rodent models of hepatic warm ischemia/reperfusion (WI/Rp) injury. IL-6-deficient mice (-/-) were subjected to hepatic WI and compared with C57BL/6 mice, as well as IL-6 -/- mice pretreated with recombinant IL-6 (rIL-6). The effects of rIL-6 following various periods of ischemia were further studied in models of hepatic ischemia in rats. IL-6 -/- mice had increased reperfusion injury as assessed by transaminase levels and a tissue necrosis scoring system when compared with controls, an effect prevented by pretreatment with rIL-6. Similarly, rats pretreated with rIL-6 had reduced reperfusion injury and better survival than controls in each respective WI group. Tissue TNF-alpha expression measured by Northern blot analysis and serum C-reactive protein (CRP) levels, a marker of inflammation, were significantly reduced in animals pretreated with rIL-6. Administration of antibodies to TNF-alpha reproduced the beneficial effect of rIL-6. Hepatocyte proliferation, as assessed by a scoring method for mitotic index and proliferating nuclear cell antigen staining, was markedly increased in rIL-6-treated rats when compared with controls. In conclusion, this study suggests that IL-6 could play an important role in limiting hepatic warm ischemia/reperfusion (WI/Rp) injury, probably through its anti-inflammatory properties, modulation of TNF-alpha, and/or promotion of liver regeneration. rIL-6 might become an important cytokine in clinical situations associated with WI/Rp injury.

Donor-derived IP-10 initiates development of acute allograft rejection

An allograft is often considered an immunologically inert playing field on which host leukocytes assemble and wreak havoc. However, we demonstrate that graft-specific physiologic responses to early injury initiate and promulgate destruction of vascularized grafts. Serial analysis of allografts showed that intragraft expression of the three chemokine ligands for the CXC chemo-kine receptor CXCR3 was induced in the order of interferon (IFN)-gamma-inducible protein of 10 kD (IP-10, or CXCL10), IFN-inducible T cell alpha-chemoattractant (I-TAC; CXCL11), and then monokine induced by IFN-gamma (Mig, CXCL9). Initial IP-10 production was localized to endothelial cells, and only IP-10 was induced by isografting. Anti-IP-10 monoclonal antibodies prolonged allograft survival, but surprisingly, IP-10-deficient (IP-10(-/-)) mice acutely rejected allografts. However, though allografts from IP-10(+/+) mice were rejected by day 7, hearts from IP-10(-/-) mice survived long term. Compared with IP-10(+/+) donors, use of IP-10(-/-) donors reduced intragraft expression of cytokines, chemokines and their receptors, and associated leukocyte infiltration and graft injury. Hence, tissue-specific generation of a single chemokine in response to initial ischemia/reperfusion can initiate progressive graft infiltration and amplification of multiple effector pathways, and targeting of this proximal chemokine can prevent acute rejection. These data emphasize the pivotal role of donor-derived IP-10 in initiating alloresponses, with implications for tissue engineering to decrease immunogenicity, and demonstrate that chemokine redundancy may not be operative in vivo.

Inactivation of Kupffer cells prevents early alcohol-induced liver injury

It is well recognized that consumption of alcohol leads to liver disease in a dose-dependent manner; however, the exact mechanisms remain unclear. Hypoxia subsequent to a hypermetabolic state may be involved; therefore, when it was observed recently that inactivation of Kupffer cells prevented stimulation of hepatic oxygen uptake by alcohol, the idea that Kupffer cells participate in early events that ultimately lead to alcohol-induced liver disease became a real possibility. The purpose of this study was to test that hypothesis. Male Wistar rats were exposed to ethanol continuously by means of intragastric feeding for up to 4 weeks using the model developed by Tsukamoto and French. In this model, ethanol causes fatty liver, necrosis and inflammation--changes characteristic of alcohol-induced liver disease in human beings. Kupffer cells were inactivated by twice weekly treatment with gadolinium chloride (GdCl3), a selective Kupffer cell toxicant. AST levels were elevated to 192 +/- 13 and 244 +/- 56 IU/L in rats exposed to ethanol for 2 and 4 wk, respectively (control value, 88 +/- 7). This injury was prevented almost completely by GdCl3 treatment. Fatty changes, inflammation and necrosis were also all reduced dramatically by GdCl3 treatment. The average hepatic pathological score of rats treated with ethanol for 4 wk was 4.3 +/- 0.6, which was reduced significantly in ethanol- and GdCl3-treated rats to 1.8 +/- 0.5 (p < 0.05). Rates of ethanol elimination were elevated 2- to 3-fold in rats exposed to ethanol for 2 to 4 wk. This elevation was blocked by GdCl3 treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Importance of ICOS-B7RP-1 costimulation in acute and chronic allograft rejection

Primary T cell activation requires B7-CD28 and CD40-CD154 costimulation, but effector T cell functions are considered to be largely independent of these costimulatory pathways. Although blockade of costimulation with cytolytic T lymphocyte-associated antigen 4-immunoglobulin (CTLA-4-Ig) or monoclonal antibody (mAb) to CD154 prolongs allograft survival, chronic rejection follows, which suggests that additional key costimulatory pathways are active in vivo. We found that both antibody to inducible costimulator (anti-ICOS) and an ICOS-Ig fusion protein suppressed intragraft T cell activation and cytokine expression and prolonged allograft survival in a manner similar to that in ICOS-/- allograft recipients. The combination of anti-ICOS therapy and cyclosporin A led to permanent engraftment. In addition, ICOS-B7RP-1 costimulation was required for the development of chronic rejection after CD40-CD154 blockade. These data demonstrate a key role for the ICOS-B7RP-1 pathway in acute and chronic rejection and highlight the benefits of targeting this pathway in combination with the use of conventional immunosuppressive agent.

Apoptosis of sinusoidal endothelial cells is a critical mechanism of preservation injury in rat liver transplantation

In livers excised for transplantation, sinusoidal endothelium appears especially vulnerable to injury during organ preservation in the cold and subsequent reperfusion. The degree of endothelial cell injury correlates with functional impairment of the graft following transplantation. The mechanism of injury remains obscure, but endothelial cell damage has been described as coagulative necrosis secondary to irreversible physico-chemical damage. We investigated whether endothelial cell death is caused by apoptosis rather than by necrosis. Tissue from rat livers stored for varying periods in cold (1 degree C) Euro-Collins solution and then reperfused for 1 hour at 37 degrees C were studied for evidence of apoptosis by detection of DNA fragmentation using the in situ terminal deoxynucleotidyl transferase d-uridine triphosphate nick end labeling (TUNEL) assay, DNA gel electrophoresis, and by transmission electron microscopy (EM). DNA fragmentation of the type characteristic of apoptosis was identified in 49.7% +/- 2.2% of sinusoidal lining cells after 8 hours of ischemia + reperfusion (viable graft) vs. 70.7% +/- 4.3% after 16 hours + reperfusion (nonviable graft) (P < .001). No such fragmentation was observed after cold preservation without reperfusion or in unpreserved, reperfused livers. EM demonstrated changes characteristic of apoptosis exclusively in endothelial cells. The study suggests that the apoptosis of sinusoidal endothelial cells is a pivotal mechanism of preservation injury in liver transplantation.

Contrasting effects of cyclosporine and rapamycin in de novo generation of alloantigen-specific regulatory T cells

The outcome of T-cell-mediated responses, immunity or tolerance, critically depends on the balance of cytopathic versus regulatory T (T(reg)) cells. In the creation of stable tolerance to MHC incompatible allografts, reducing the unusually large mass of donor-reactive cytopathic T effector (T(eff)) cells via apoptosis is often required. Cyclosporine (CsA) blocks activation-induced cell death (AICD) of T(eff) cells, and is detrimental to tolerance induction by costimulation blockade, whereas Rapamycin (RPM) preserves AICD, and augments the potential of costimulation blockade to create tolerance. While differences between CsA and RPM in influencing apoptosis of activated graft-destructive T(eff) cells are apparent, their effects on graft-protective T(reg) cells remain enigmatic. Moreover, it is unclear whether tolerizing regimens foster conversion of naïve peripheral T cells into alloantigen-specific T(reg) cells for graft protection. Here we show, using reporter mice for T(reg) marker Foxp3, that RPM promotes de novo conversion of alloantigen-specific T(reg) cells, whereas CsA completely inhibits this process. Upon transfer, in vivo converted T(reg) cells potently suppress the rejection of donor but not third party skin grafts. Thus, the differential effects of RPM and CsA on T(eff) and T(reg) cells favor the use of RPM in shifting the balance of aggressive to protective type alloimmunity.

Temporal and spatial development of axonal maturation and myelination of white matter in the developing brain

BACKGROUND AND PURPOSE

Diffusion tensor imaging (DTI) has been widely used to investigate the development of white matter (WM). However, information about this development in healthy children younger than 2 years of age is lacking, and most previous studies have only measured fractional anisotropy (FA). This study used FA and radial and axonal diffusivities in children younger than 2 years of age, aiming to determine the temporal and spatial development of axonal maturation and myelination of WM in healthy children.

MATERIALS AND METHODS

A total of 60 healthy pediatric subjects were imaged by using a 3T MR imaging scanner. They were divided into 3 groups: 20 at 3 weeks, 20 at 1 year of age, and 20 at 2 years of age. All subjects were imaged asleep without sedation. FA and axial and radial diffusivities were obtained. Eight regions of interest were defined, including both central and peripheral WM for measuring diffusion parameters.

RESULTS

A significant elevation in FA (P < .0001) and a reduction in axial and radial diffusivities (P < .0001) were observed from 22 days to 1 year of age, whereas only radial diffusivity showed significant changes (P = .0014) from 1 to 2 years of age. The region-of-interest analysis revealed that FA alone may not depict the underlying biologic underpinnings of WM development, whereas directional diffusivities provide more insights into the development of WM. Finally, the spatial development of WM begins from the central to the peripheral WM and from the occipital to the frontal lobes.

CONCLUSIONS

With both FA and directional diffusivities, our results demonstrate the temporal and spatial development of WM in healthy children younger than 2 years of age.

Targeting of the chemokine receptor CCR1 suppresses development of acute and chronic cardiac allograft rejection

Although mononuclear cell infiltration is a hallmark of cellular rejection of a vascularized allograft, efforts to inhibit rejection by blocking leukocyte-endothelial cell adhesion have proved largely unsuccessful, perhaps in part because of persistent generation of chemokines within rejecting grafts. We now provide, to our knowledge, the first evidence that in vivo blockade of specific chemokine receptors is of therapeutic significance in organ transplantation. Inbred mice with a targeted deletion of the chemokine receptor CCR1 showed significant prolongation of allograft survival in 4 models. First, cardiac allografts across a class II mismatch were rejected by CCR1(+/+) recipients but were accepted permanently by CCR1(-/-) recipients. Second, CCR1(-/-) mice rejected completely class I- and class II-mismatched BALB/c cardiac allografts more slowly than control mice. Third, levels of cyclosporin A that had marginal effects in CCR1(+/+) mice resulted in permanent allograft acceptance in CCR1(-/-) recipients. These latter allografts showed no sign of chronic rejection 50-200 days after transplantation, and transfer of CD4(+) splenic T cells from these mice to naive allograft recipients significantly prolonged allograft survival, whereas cells from CCR1(+/+) mice conferred no such benefit. Finally, both CCR1(+/+) and CCR1(-/-) allograft recipients, when treated with a mAb to CD4, showed permanent engraftment, but these allografts showed florid chronic rejection in the former strain and were normal in CCR1(-/-) mice. We conclude that therapies to block CCR1/ligand interactions may prove useful in preventing acute and chronic rejection clinically.

Functional connectivity MR imaging reveals cortical functional connectivity in the developing brain

BACKGROUND AND PURPOSE

Unlike conventional functional MR imaging where external sensory/cognitive paradigms are needed to specifically activate different regions of the brain, resting functional connectivity MR imaging acquires images in the absence of cognitive demands (a resting condition) and detects brain regions, which are highly temporally correlated. Therefore, resting functional MR imaging is highly suited for the study of brain functional development in pediatric subjects. This study aimed to determine the temporal and spatial patterns of rfc in healthy pediatric subjects between 2 weeks and 2 years of age.

MATERIALS AND METHODS

Rfc studies were performed on 85 children: 38 neonates (2-4 weeks of age), 26 one-year-olds, and 21 two-year-olds. All subjects were imaged while asleep; no sedation was used. Six regions of interest were chosen, including the primary motor, sensory, and visual cortices in each hemisphere. Mean signal intensity of each region of interest was used to perform correlation analysis pixel by pixel throughout the entire brain, identifying regions with high temporal correlation.

RESULTS

Functional connectivity was observed in all subjects in the sensorimotor and visual areas. The percent brain volume exhibiting rfc and the strength of rfc continued to increase from 2 weeks to 2 years. The growth trajectories of the percent brain volume of rfc appeared to differ between the sensorimotor and visual areas, whereas the z-score was similar. The percent brain volume of rfc in the sensorimotor area was significantly larger than that in the visual area for subjects 2 weeks of age (P = .008) and 1-year-olds (P = .017) but not for the 2-year-olds.

CONCLUSIONS

These findings suggest that rfc in the sensorimotor precedes that in the visual area from 2 weeks to 1 year but becomes comparable at 2 years. In contrast, the comparable z-score values between the sensorimotor and visual areas for all age groups suggest a disassociation between percent brain volume and the strength of cortical rfc.

Dysregulated bioenergetics: a key regulator of joint inflammation

OBJECTIVES

This study examines the relationship between synovial hypoxia and cellular bioenergetics with synovial inflammation.

METHODS

Primary rheumatoid arthritis synovial fibroblasts (RASF) were cultured with hypoxia, dimethyloxalylglycine (DMOG) or metabolic intermediates. Mitochondrial respiration, mitochondrial DNA mutations, cell invasion, cytokines, glucose and lactate were quantified using specific functional assays. RASF metabolism was assessed by the XF24-Flux Analyzer. Mitochondrial structural morphology was assessed by transmission electron microscopy (TEM). In vivo synovial tissue oxygen (tpO2 mmHg) was measured in patients with inflammatory arthritis (n=42) at arthroscopy, and markers of glycolysis/oxidative phosphorylation (glyceraldehyde 3-phosphate dehydrogenase (GAPDH), PKM2, GLUT1, ATP) were quantified by immunohistology. A subgroup of patients underwent contiguous MRI and positron emission tomography (PET)/CT imaging. RASF and human dermal microvascular endothelial cells (HMVEC) migration/angiogenesis, transcriptional activation (HIF1α, pSTAT3, Notch1-IC) and cytokines were examined in the presence of glycolytic inhibitor 3-(3-Pyridinyl)-1-(4-pyridinyl)-2-propen-1-one (3PO).

RESULTS

DMOG significantly increased mtDNA mutations, mitochondrial membrane potential, mitochondrial mass, reactive oxygen species and glycolytic RASF activity with concomitant attenuation of mitochondrial respiration and ATP activity (all p<0.01). This was coupled with altered mitochondrial morphology. Hypoxia-induced lactate levels (p<0.01), which in turn induced basic fibroblast growth factor (bFGF) secretion and RASF invasiveness (all p<0.05). In vivo glycolytic markers were inversely associated with synovial tpO2 levels <20 mm Hg, in contrast ATP was significantly reduced (all p<0.05). Decrease in GAPDH and GLUT1 was paralleled by an increase in in vivo tpO2 in tumour necrosis factor alpha inhibitor (TNFi) responders. Novel PET/MRI hybrid imaging demonstrated close association between metabolic activity and inflammation. 3PO significantly inhibited RASF invasion/migration, angiogenic tube formation, secretion of proinflammatory mediators (all p<0.05), and activation of HIF1α, pSTAT3 and Notch-1IC under normoxic and hypoxic conditions.

CONCLUSIONS

Hypoxia alters cellular bioenergetics by inducing mitochondrial dysfunction and promoting a switch to glycolysis, supporting abnormal angiogenesis, cellular invasion and pannus formation.

Reperfusion after liver transplantation in rats differentially activates the mitogen-activated protein kinases

The injury resulting from cold ischemia and warm reperfusion during liver transplantation is a major clinical problem that limits graft success. Kupffer cell activation plays a pivotal role in reperfusion injury, and Kupffer cell products, including free radicals and tumor necrosis factor alpha (TNF-alpha), are implicated as damaging agents. However, the second messengers and signaling pathways that are activated by the stress of hepatic ischemia/reperfusion remain unknown. The purpose of this study is to assess the activation of the three known vertebrate mitogen activated protein kinase (MAPKs) and the activating protein 1 (AP-1) transcription factor in response to ischemia and reperfusion in the transplanted rat liver. There was a potent, sustained induction of c-jun N-terminal kinase (JNK), but not of the related MAPKs extracellular signal-regulated kinases (ERK) or p38, upon reperfusion after transplantation. TNF-alpha messenger RNA (mRNA) levels and transcription factors AP-1 and nuclear factor-kappaB (NF-kappaB) were induced in the liver after 60 minutes of reperfusion. Finally, there was an elevation of ceramide, but not diacylglycerol or sphingosine, in the transplanted liver. Ceramide is a second messenger generated by TNF-alpha treatment and is an activator of JNK. Because JNK activation preceded the elevations in ceramide and TNF-alpha mRNA, these results suggest that increased hepatic TNF-alpha and ceramide may perpetuate JNK induction, but that they are not the initiating signals of JNK activation during reperfusion injury in the transplanted liver.

Increasing prevalence of gestational diabetes mellitus in Chinese women from 1999 to 2008

AIMS

To investigate the trend in the prevalence of gestational diabetes mellitus during 1999-2008 in women living in urban Tianjin, China.

METHODS

A universal screening for gestational diabetes mellitus has become an integral part of the antenatal care in Tianjin, China from 1998. A total of 105,473 pregnant women living in the six urban districts of Tianjin, China, participated in the gestational diabetes mellitus screening programme between December 1998 and December 2008. The screening test consisted of a 50-g 1-h glucose test. Women who had a glucose reading ≥7.8 mmol/l at the initial screening were invited to undergo the standard 2-h oral glucose tolerance test with a 75-g glucose load. Gestational diabetes mellitus was confirmed using the World Health Organization's diagnostic criteria.

RESULTS

The adjusted prevalence of gestational diabetes mellitus increased by 2.8 times during 1999-2008, from 2.4 to 6.8% (P<0.0001 for linear trend). In 2008, the age-specific prevalence of gestational diabetes mellitus was the highest among women aged 30-34 years (11.3%) and lowest among women aged 25 and under (1.2%). In women aged 35 years and more, the prevalence was 5.3%.

CONCLUSIONS

The prevalence of gestational diabetes mellitus has markedly been increasing in a universally screened urban Chinese female population and has become an important public health problem in China.

Beneficial effects of targeting CCR5 in allograft recipients

BACKGROUND

The chemokine receptor, CCR5, and its three high-affinity ligands, macrophage inflammatory protein- (MIP) 1alpha, MIP-1beta, and regulated on activation normal T cell expressed and secreted (RANTES), are expressed by infiltrating mononuclear cells during the rejection of clinical and experimental organ allografts, although the significance of these molecules in the pathogenesis of rejection has not been established.

METHODS

We studied intragraft events in four allograft models. First, we studied cardiac transplants in fully MHC-mismatched mice that were deficient in CCR5 or two of its ligands, MIP-1alpha or RANTES. Second we tested the effects of a neutralizing rat anti-mCCR5 monoclonal antibody on allograft survival. Third we assessed whether a subtherapeutic course of cyclosporine would potentiate enhance survival in CCR5-deficient recipients. Finally, we tested the effect of targeting CCR5 in a class II-mismatched model.

RESULTS

Whereas mice deficient in expression of MIP-1alpha or RANTES reject fully MHC-mismatched cardiac allografts normally, CCR5-/- mice, or CCR5+/+ mice treated with a neutralizing mAb to mCCR5, show enhanced allograft survival. MHC class II-disparate mismatched are permanently accepted in CCR5-/- but not CCR5+/+ recipients. Finally, the beneficial effects of targeting of CCR5 are markedly synergistic with the effects of cyclosporine, resulting in permanent engraftment without development of chronic rejection.

CONCLUSIONS

We conclude that CCR5 plays a key role in the mechanisms of host T cell and macrophage recruitment and allograft rejection, such that targeting of CCR5 clinically may be of therapeutic significance.

Chemokines and their receptors in allograft rejection

Despite current recognition of over 40 chemokines and more than 18 chemokine receptors, understanding of their role in transplant immunobiology and transplant rejection is extremely limited and fragmentary. Recent literature has demonstrated the presence of chemokines and their receptors in transplants and some studies demonstrate important functional roles.

Differential effects of cyclosporine A, methylprednisolone, mycophenolate, and rapamycin on CD154 induction and requirement for NFkappaB: implications for tolerance induction

BACKGROUND

Recent experimental data indicate that the targeting of the costimulatory molecule CD40-ligand (CD154) may well offer an opportunity for tolerance induction in transplant recipients and patients with autoimmune diseases, although the optimal therapeutic strategy for clinical application of CD154 monoclonal antibody (mAb) is unclear.

METHODS

We undertook vascularized heterotopic cardiac allograft transplantation in completely MHC-mismatched mice, treated recipients with CD154 mAb plus various immunosuppressive agents, and performed flow cytometric analysis of CD154 expression by T cells activated in vitro in the presence of corresponding immunosuppressive agents. We also tested the extent to which CD154 induction was NFkappaB-dependent by using NFkappaB/p50-deficient mice as allograft recipients and as source of cells for in vitro studies of CD154 induction, and through use of proteasome inhibitors to block IkappaBalpha degradation and NFKB activation in wild-type mice.

RESULTS

Concomitant use of cyclosporin A or methylprednisolone, but not rapamycin or mycophenolate, inhibited CD154 mAb-induced allograft survival. The differential effects of these agents on CD154 mAb-induced tolerance correlated with their capacity to inhibit activation-induced CD154 expression on CD4+ T cells. Full expression of CD154 expression was found to require NF-kappaB activation, and CD154 mAb was ineffective in NF-kappaB/p50 deficient allograft recipients or control mice in which NF-kappaB activation was blocked by proteasome inhibition.

CONCLUSIONS

Strategies to use CD154 mAb clinically must take into account the effects of immunosuppressive agents on CD154 induction, which seems to be at least partially NF-kappaB dependent. Our data suggest that ligation of surface-expressed CD154 provides an important signal that modulates T cell activation and thereby contributes to the effects of CD154 mAb, in addition to previously recognized actions involving blockade of CD40/CD154-dependent cell activation and activation-induced cell death.

Permeability barrier disorder in Niemann-Pick disease: sphingomyelin-ceramide processing required for normal barrier homeostasis

Prior studies have established the requirement for enzymatic hydrolysis of glucosylceramides to ceramide for epidermal barrier homeostasis. In this study, we asked whether sphingomyelin-derived ceramide, resulting from acid-sphingomyelinase activity, is also required for normal barrier function. We showed first, that a subset of Niemann-Pick patients with severe acid-sphingomyelinase deficiency (i.e., <2% residual activity) demonstrate abnormal permeability barrier homeostasis, i.e., delayed recovery kinetics following acute barrier disruption by cellophane tape-stripping. To obtain further mechanistic insights into the potential requirement for sphingomyelin-to-ceramide processing for the barrier, we next studied the role of acid-sphingomyelinase in hairless mouse skin. Murine epidermis contains abundant acid-sphingomyelinase activity (optimal pH 5.1-5.6). Two hours following acute barrier disruption by tape-stripping, acid-sphingomyelinase activity increases 1. 44-fold (p<0.008 versus vehicle-treated controls), an increase that is blocked by a single topical application of the acid-sphingomyelinase inhibitor, palmitoyldihydrosphingosine. Furthermore, both palmitoyldihydrosphingosine and desipramine, a chemically and mechanically unrelated acid-sphingomyelinase inhibitor, significantly delay barrier recovery both 2 and 4 h after acute barrier abrogation. Inhibitor application also causes both an increase in sphingomyelin content, and a reduction of normal extracellular lamellar membrane structures, in the stratum corneum. Both of the inhibitor-induced delays in barrier recovery can be overridden by co-applications of topical ceramide, demonstrating that an alteration of the ceramide-sphingomyelin ratio, rather than sphingomyelin accumulation, is likely responsible for the barrier abnormalities that occur with acid-sphingomyelinase deficiency. These studies demonstrate an important role for enzymatic processing of sphingomyelin-to-ceramide by acid-sphingomyelinase as a mechanism for generating a portion of the stratum corneum ceramides for permeability barrier homeostasis in mammalian skin.

Targeted deletion of CX(3)CR1 reveals a role for fractalkine in cardiac allograft rejection

Fractalkine (Fk) is a structurally unusual member of the chemokine family. To determine its role in vivo, we generated mice with a targeted disruption of CX(3)CR1, the receptor for Fk. CX(3)CR1(-/-) mice were phenotypically indistinguishable from wild-type mice in a pathogen-free environment. In response to antibody-induced glomerulonephritis, CX(3)CR1(-/-) and CX(3)CR1(+/+) mice had similar levels of proteinuria and injury. CX(3)CR1(-/-) and CX(3)CR1(+/+) mice also developed similar levels of disease in myelin oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis. We performed heterotopic MHC class I/II cardiac transplants from BALB/c mice into C57BL/6 mice. In the absence of cyclosporin A (CsA), there was no difference in graft survival time between CX(3)CR1(-/-) and CX(3)CR1(+/+) recipient mice. However, in the presence of subtherapeutic levels of CsA, graft survival time was significantly increased in the CX(3)CR1(-/-) mice. Characterization of cells infiltrating the grafts revealed a selective reduction in natural killer cells in the CX(3)CR1(-/-) recipients in the absence of CsA and a reduction in macrophages, natural killer cells, and other leukocytes in the presence of CsA. We conclude that Fk plays an important role in graft rejection. The development of CX(3)CR1 antagonists may allow reductions in the doses of immunosuppressive drugs used in transplantation.

Senolytic agent Quercetin ameliorates intervertebral disc degeneration via the Nrf2/NF-κB axis

OBJECTIVE

Intervertebral disc degeneration (IDD) represents major cause of low back pain. Quercetin (QUE) is one of the approved senolytic agents. In this study, we evaluated the protective effects of QUE on IDD development and its underlying mechanism.

METHODS

Effects of senolytic agent QUE on the viability of nucleus pulposus cells (NPCs) were measured by CCK-8 assays and EdU staining. The senescence associated secreted phenotype (SASP) factors expressions were measured by qPCR, western blot, and ELISA; and NF-κB pathway was detected by immunofluorescence and western blot. Molecular docking was applied to predict the interacting protein of QUE; while Nrf2 was knocked down by siRNAs to confirm its role in QUE regulated senescence phenotype. X-ray, MRI, Hematoxylin-Eosin and Safranin O-Fast green staining were performed to evaluate the therapeutic effects of QUE on IDD in the puncture-induced rat model.

RESULTS

In in vitro experiments, QUE inhibited SASP factors expression and senescence phenotype in IL-1β-treated NPCs. Mechanistically, QUE suppressed IL-1β induced activation of the NF-κB pathway cascades; it was also demonstrated in molecular docking and knock down studies that QUE might bind to Keap1-Nrf2 complex to suppress NF-κB pathway. In vivo, QUE ameliorated the IDD process in the puncture-induced rat model.

CONCLUSIONS

Together the present work suggests that QUE inhibits SASP factors expression and senescence phenotype in NPCs and ameliorates the progression of IDD via the Nrf2/NF-κB axis, which supports senolytic agent QUE as a potential therapeutic agent for the treatment of IDD.

Tofacitinib regulates synovial inflammation in psoriatic arthritis, inhibiting STAT activation and induction of negative feedback inhibitors

BACKGROUND

Psoriatic arthritis (PsA) is a chronic inflammatory disease, characterised by synovitis and destruction of articular cartilage/bone. Janus-kinase and signal transducer and activator of transcription (JAK-STAT) signalling pathway is implicated in the pathogenesis of PsA.

OBJECTIVES

To examine the effect of tofacitinib (JAK inhibitor) on proinflammatory mechanisms in PsA.

METHODS

Primary PsA synovial fibroblasts (PsAFLS) and ex vivo PsA synovial explants were cultured with tofacitinib (1 µM). PhosphoSTAT3 (pSTAT3), phosphoSTAT1 (pSTAT1), suppressor of cytokine signaling-3 (SOCS3), protein inhibitor of activated Stat3 (PIAS3) and nuclear factor kappa B cells (NFκBp65) were quantified by western blot. The effect of tofacitinib on PsAFLS migration, invasion, Matrigel network formation and matrix metallopeptidase (MMP)2/9 was quantified by invasion/migration assays and zymography. Interleukin (IL)-6, IL-8, IFN-gamma-inducible protein 10 (IP-10) monocyte chemoattractant protein (MCP)-1, IL-17, IL-10, MMP3 and tissue inhibitor of metalloproteinases 3 (TIMP3) were assessed by ELISA.

RESULTS

Tofacitinib significantly decreased pSTAT3, pSTAT1, NFκBp65 and induced SOCS3 and PIAS3 expression in PsAFLS and synovial explant cultures (p<0.05). Functionally, PsAFLS invasion, network formation and migration were inhibited by tofacitinib (all p<0.05). In PsA explant, tofacitinib significantly decreased spontaneous secretion of IL-6, IL-8, MCP-1, MMP9/MMP2, MMP3 (all p<0.05) and decreased the MMP3/TIMP3 ratio (p<0.05), with no effect observed for IP-10 or IL-10.

CONCLUSIONS

This study further supports JAK-STAT inhibition as a therapeutic target for the treatment of PsA.