CD44-deficient mice exhibit enhanced hepatitis after concanavalin A injection: evidence for involvement of CD44 in activation-induced cell death

6-Formylindolo[3,2-b]carbazole, a potent ligand for the aryl hydrocarbon receptor, attenuates concanavalin-induced hepatitis by limiting T-cell activation and infiltration of proinflammatory CD11b+ Kupffer cells

FICZ (6-formylindolo[3,2-b]carbazole) is a potent aryl hydrocarbon receptor agonist that has a poorly understood function in the regulation of inflammation. In this study, we investigated the effect of aryl hydrocarbon receptor activation by FICZ in a murine model of autoimmune hepatitis induced by concanavalin A. High-throughput sequencing techniques such as single-cell RNA sequencing and assay for transposase accessible chromatin sequencing were used to explore the mechanisms through which FICZ induces its effects. FICZ treatment attenuated concanavalin A-induced hepatitis, evidenced by decreased T-cell infiltration, decreased circulating alanine transaminase levels, and suppression of proinflammatory cytokines. Concanavalin A revealed an increase in natural killer T cells, T cells, and mature B cells upon concanavalin A injection while FICZ treatment reversed the presence of these subsets. Surprisingly, concanavalin A depleted a subset of CD55+ B cells, while FICZ partially protected this subset. The immune cells showed significant dysregulation in the gene expression profiles, including diverse expression of migratory markers such as CCL4, CCL5, and CXCL2 and critical regulatory markers such as Junb. Assay for transposase accessible chromatin sequencing showed more accessible chromatin in the CD3e promoter in the concanavalin A-only group as compared to the naive and concanavalin A-exposed, FICZ-treated group. While there was overall more accessible chromatin of the Adgre1 (F4/80) promoter in the FICZ-treated group, we observed less open chromatin in the Itgam (CD11b) promoter in Kupffer cells, supporting the ability of FICZ to reduce the infiltration of proinflammatory cytokine producing CD11b+ Kupffer cells. Taken together, these data demonstrate that aryl hydrocarbon receptor activation by FICZ suppresses liver injury through the limitation of CD3+ T-cell activation and CD11b+ Kupffer cell infiltration.

AhR Activation Leads to Attenuation of Murine Autoimmune Hepatitis: Single-Cell RNA-Seq Analysis Reveals Unique Immune Cell Phenotypes and Gene Expression Changes in the Liver

The aryl hydrocarbon receptor (AhR) is a ubiquitously expressed ligand-activated transcription factor. While initially identified as an environmental sensor, this receptor has been shown more recently to regulate a variety of immune functions. AhR ligands vary in structure and source from environmental chemicals such as 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) and indoles found in cruciferous vegetables to endogenous ligands derived from tryptophan metabolism. In the current study, we used TCDD, a high affinity AhR ligand to study the impact of AhR activation in the murine model of autoimmune hepatitis (AIH). Primarily, we used single-cell RNA-sequencing (scRNA-seq) technology to study the nature of changes occurring in the immune cells in the liver at the cellular and molecular level. We found that AhR activation attenuated concanavalin A (ConA)-induced AIH by limiting chemotaxis of pro-inflammatory immune cell subsets, promoting anti-inflammatory cytokine production, and suppressing pro-inflammatory cytokine production. scRNA-seq analysis showed some unusual events upon ConA injection such as increased presence of mature B cells, natural killer (NK) T cells, CD4+ or CD8+ T cells, Kupffer cells, memory CD8+ T cells, and activated T cells while TCDD treatment led to the reversal of most of these events. Additionally, the immune cells showed significant alterations in the gene expression profiles. Specifically, we observed downregulation of inflammation-associated genes including Ptma, Hspe1, and CD52 in TCDD-treated AIH mice as well as alterations in the expression of migratory markers such as CXCR2. Together, the current study characterizes the nature of inflammatory changes occurring in the liver during AIH, and sheds light on how AhR activation during AIH attenuates liver inflammation by inducing phenotypic and genotypic changes in immune cells found in the liver.

Increased Regeneration Following Stress-Induced Lung Injury in Bleomycin-Treated Chimeric Mice with CD44 Knockout Mesenchymal Cells

CD44, an adhesion-molecule promoting cell-migration, is shown here to increase in stress conditions following bleomycin-induced apoptosis in alveolar epithelial cells (AECs), a main target of lung injury. In vivo, it inhibits tissue regeneration and leads to fibrosis. We show that some AECs survive by the ataxia-telangiectasia mutated kinase/ATM pathway, and undergo a CD44-mediated epithelial-mesenchymal transdifferentiation (EMT) with migratory capacities in vitro, and in vivo. We assessed apoptosis vs. proliferation of AECs following bleomycin, ATM/P53 signaling pathway in AECs, and CD44 involvement in EMT, cell motility and tissue regeneration in vitro and in vivo. Expression of survival genes, CD44, and ATM/p53 pathway was elevated in AECs surviving bleomycin injury, as were the markers of EMT (downregulation of E-cadherin, upregulation of N-cadherin and vimentin, nuclear translocation of β-catenin). Inhibition of CD44 decreased AECs transdifferentiation. Bleomycin-treated chimeric CD44^KO-mice had decreased EMT markers, ATM, and mesenchymal cells (α-SMA⁺) accumulation in lung, increased surfactant-b, diminished lung mesenchymal cell motility, and increased lung tissue regenerative capacity following bleomycin injury, as indicated by lung collagen content and semiquantitave morphological index scoring. Thus, AECs surviving lung injury are plastic and undergo ATM-mediated, CD44-dependent transdifferentiation, preventing tissue regeneration and promoting fibrosis. Synthetic or natural compounds that downregulate CD44 may improve tissue regeneration following injury.

Hepatoprotective Effects of Lactobacillus on Carbon Tetrachloride-Induced Acute Liver Injury in Mice

The aim of this study was to investigate and compare the effects of heat-killed and live Lactobacillus on carbon tetrachloride (CCl₄)-induced acute liver injury mice. The indexes evaluated included liver pathological changes, the levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), superoxide dismutase (SOD), glutathione (GSH), and malondialdehyde (MDA) in the serum, related gene expression (IL-1β, TNF-α, Bcl-2, and Bax), and related proteins levels (Bax, Bcl-2, Caspase 3, and NF-κB p65). Compared with the model group, the results indicated that the levels of ALT, AST, and MDA in the serum, the expression levels of IL-1β, TNF-α, and Bax, and the protein levels of Bax, Caspase 3, and NF-κB p65 significantly decreased, and the pathologic damage degree all significantly reduced after live Lactobacillus fermentum (L-LF) and live Lactobacillus plantarum (L-LP) treatment. Additionally, the levels of SOD and GSH in the serum, the gene expression of Bcl-2, and the protein level of Bcl-2 significantly increased after L-LF and L-LP treatment. Although HK-LF and HK-LP could also have obvious regulating effects on some of the evaluated indexes (ALT, AST, the expression levels of TNF-α and Bax, and the protein level of Bcl-2) and play an important role in weakening liver damage, the regulating effects of L-LF or L-LP on these indexes were all better compared with the corresponding heat-killed Lactobacillus fermentum (HK-LF) and heat-killed Lactobacillus plantarum (HK-LP). Therefore, these results suggested that LF and LP have an important role in liver disease.

Unique CD44 intronic SNP is associated with tumor grade in breast cancer: a case control study and in silico analysis

Background

CD44 encoded by a single gene is a cell surface transmembrane glycoprotein. Exon 2 is one of the important exons to bind CD44 protein to hyaluronan. Experimental evidences show that hyaluronan–CD44 interaction intensifies the proliferation, migration, and invasion of breast cancer cells. Therefore, the current study aimed at investigating the association between specific polymorphisms in exon 2 and its flanking region of CD44 with predisposition to breast cancer.

Methods

In the current study, 175 Iranian female patients with breast cancer and 175 age-matched healthy controls were recruited in biobank, Breast Cancer Research Center, Tehran, Iran. Single nucleotide polymorphisms of CD44 exon 2 and its flanking were analyzed via polymerase chain reaction and gene sequencing techniques. Association between the observed variation with breast cancer risk and clinico-pathological characteristics were studied. Subsequently, bioinformatics analysis was conducted to predict potential exonic splicing enhancer (ESE) motifs changed as the result of a mutation.

Results

A unique polymorphism of the gene encoding CD44 was identified at position 14 nucleotide upstream of exon 2 (A37692→G) by the sequencing method. The A > G polymorphism exhibited a significant association with higher-grades of breast cancer, although no significant relation was found between this polymorphism and breast cancer risk. Finally, computational analysis revealed that the intronic mutation generated a new consensus-binding motif for the splicing factor, SC35, within intron 1.

Conclusions

The current study results indicated that A > G polymorphism was associated with breast cancer development; in addition, in silico analysis with ESE finder prediction software showed that the change created a new SC35 binding site.

Comparative Analysis of Mesenchymal Stem Cells from Bone Marrow, Adipose Tissue, and Dental Pulp as Sources of Cell Therapy for Zone of Stasis Burns

Introduction: The implantation of mesenchymal stem cells (MSCs) has been shown to exert benefits for the survival of the zone-of-stasis. However, the clinical experience indicates the importance of selecting the right source and type of stem cells. Therefore, we planned the current study to perform a quantitative comparison of MSCs isolated from three different sources to provide information useful in selection of the optimal source and to see whether critical mechanisms are conserved between different populations. Methods: The protective effects of MSCs derived from bone marrow, adipose tissue and dental pulp were compared in a rat model of thermal trauma. The stasis zones were evaluated 72 h after the burn using histochemistry, immunohistochemistry and biochemistry. Results: Gross evaluation of burn wounds revealed that the differences between the mean percentages of the calculated necrotic areas weren't statistically significant. Semi-quantitative grading of the histopathological findings revealed that there were no significant differences between damage scores. Immunohistochemical assessment of apoptotic and necrotic cell deaths revealed that the differences between the mean numbers of apoptotic and necrotic cells weren't statistically significant. Myeloperoxidase activity was found to be significantly lower in the adipose tissue group. Biochemical and immunohistochemical assessment of tissue malondialdehyde revealed that the differences between the groups weren't statistically significant. Finally, the number of neo-vessels in the dental pulp group was found to be significantly higher. Conclusion: Our findings suggest that bone marrow, adipose tissue and dental pulp may serve as a universal donor MSC source for the prevention of burn wound progression.

CD44 deletion leading to attenuation of experimental autoimmune encephalomyelitis results from alterations in gut microbiome in mice

Dysbiosis in gut microbiome has been shown to be associated with inflammatory and autoimmune diseases. Previous studies from our laboratory demonstrated the pivotal role played by CD44 in the regulation of EAE, a murine model of multiple sclerosis. In the current study, we determined whether these effects resulted from an alteration in gut microbiota and the short-chain fatty acid (SCFA) production in CD44 knockout (CD44KO) mice. Fecal transfer from naïve CD44KO but not C57BL/6 wild type (CD44WT) mice, into EAE-induced CD44WT mice, led to significant amelioration of EAE. High-throughput bacterial 16S rRNA gene sequencing, followed by clustering sequences into operational taxonomic units (OTUs) and biochemical analysis, revealed that EAE-induced CD44KO mice showed significant diversity, richness, and evenness when compared to EAE-induced CD44WT mice at the phylum level, with dominant Bacteroidetes (68.5%) and low Firmicutes (26.8%). Further, data showed a significant change in the abundance of SCFAs, propionic acid, and i-butyric acid in EAE-CD44KO compared to EAE-CD44WT mice. In conclusion, our results demonstrate that the attenuation of EAE seen following CD44 gene deletion in mice may result from alterations in the gut microbiota and SCFAs. Furthermore, our studies also demonstrate that the phenotype of gene knock-out animals may be shaped by gut microbiota.

Hyaluronan as a therapeutic target in human diseases

Accumulation and turnover of extracellular matrix is a hallmark of tissue injury, repair and remodeling in human diseases. Hyaluronan is a major component of the extracellular matrix and plays an important role in regulating tissue injury and repair, and controlling disease outcomes. The function of hyaluronan depends on its size, location, and interactions with binding partners. While fragmented hyaluronan stimulates the expression of an array of genes by a variety of cell types regulating inflammatory responses and tissue repair, cell surface hyaluronan provides protection against tissue damage from the environment and promotes regeneration and repair. The interactions of hyaluronan and its binding proteins participate in the pathogenesis of many human diseases. Thus, targeting hyaluronan and its interactions with cells and proteins may provide new approaches to developing therapeutics for inflammatory and fibrosing diseases. This review focuses on the role of hyaluronan in biological and pathological processes, and as a potential therapeutic target in human diseases.

Roles of Proteoglycans and Glycosaminoglycans in Wound Healing and Fibrosis

A wound is a type of injury that damages living tissues. In this review, we will be referring mainly to healing responses in the organs including skin and the lungs. Fibrosis is a process of dysregulated extracellular matrix (ECM) production that leads to a dense and functionally abnormal connective tissue compartment (dermis). In tissues such as the skin, the repair of the dermis after wounding requires not only the fibroblasts that produce the ECM molecules, but also the overlying epithelial layer (keratinocytes), the endothelial cells, and smooth muscle cells of the blood vessel and white blood cells such as neutrophils and macrophages, which together orchestrate the cytokine-mediated signaling and paracrine interactions that are required to regulate the proper extent and timing of the repair process. This review will focus on the importance of extracellular molecules in the microenvironment, primarily the proteoglycans and glycosaminoglycan hyaluronan, and their roles in wound healing. First, we will briefly summarize the physiological, cellular, and biochemical elements of wound healing, including the importance of cytokine cross-talk between cell types. Second, we will discuss the role of proteoglycans and hyaluronan in regulating these processes. Finally, approaches that utilize these concepts as potential therapies for fibrosis are discussed.

Association of CD44 Gene Polymorphism with Survival of NSCLC and Risk of Bone Metastasis

Background

Previous studies have reported CD44 expression influenced the development and progression of tumors. The aim of this study was to investigate whether single-nucleotide polymorphisms (SNPs) of the CD44 gene are associated with survival of non-small cell lung cancer (NSCLC) and occurrence rate of bone metastasis.

Material/Methods

A total of 234 patients with NSCLC between 2003 and 2010 were enrolled in this study and 468 healthy persons were used as controls. Two polymorphisms, rs13347 and rs187115, in the CD44 gene were genotyped using DNA from blood lymphocytes. For statistical analysis we used the chi-square test, Fisher’s exact test, Kaplan-Meier method, and log-rank test.

Results

CD44 gene rs13347 polymorphism was not associated with NSCLC risk. For rs187115, the association with NSCLC risk was observed (P<0.001). Allele G carriers had significantly higher occurrence rates of bone metastasis (OR=0.4, 95%CI: 0.20–0.64, P<0.001) and more advanced tumor stage (OR=2.6, 95%CI: 1.50–4.45, P=0.001) compared to carriers of allele A. The survival rates for patients with AA genotype were significantly higher than for patients with the AG+GG genotypes (P<0.001). In multivariate analysis of survival in NSCLC patients, significant predictors were CD44 gene (AG+GG) (RR=0.48, 95%CI: 0.34–0.68, P<0.001), tumor stage (RR=0.45, 95%CI: 0. 0.31–0.65, P<0.001), and bone metastasis (RR=1.52, 95%CI: 1.05–2.21, P=0.027).

Conclusions

CD44 gene rs187115 polymorphism is a potential predictive marker of survival in NSCLC patients, and is significantly correlated with bone metastasis and tumor stage.

Sensitization to autoimmune hepatitis in group VIA calcium-independent phospholipase A2-null mice led to duodenal villous atrophy with apoptosis, goblet cell hyperplasia and leaked bile acids

Chronic bowel disease can co-exist with severe autoimmune hepatitis (AIH) in an absence of primary sclerosing cholangitis. Genetic background may contribute to this overlap syndrome. We previously have shown that the deficiency of iPLA2β causes an accumulation of hepatocyte apoptosis, and renders susceptibility for acute liver injury. We here tested whether AIH induction in iPLA2β-null mice could result in intestinal injury, and whether bile acid metabolism was altered. Control wild-type (WT) and female iPLA2β-null (iPLA2β(-/-)) mice were intravenously injected with 10mg/kg concanavalinA (ConA) or saline for 24h. ConA treatment of iPLA2β(-/-) mice caused massive liver injury with increased liver enzymes, fibrosis, and necrosis. While not affecting WT mice, ConA treatment of iPLA2β(-/-) mice caused severe duodenal villous atrophy concomitant with increased apoptosis, cell proliferation, globlet cell hyperplasia, and endotoxin leakage into portal vein indicating a disruption of intestinal barrier. With the greater extent than in WT mice, ConA treatment of iPLA2β(-/-) mice increased jejunal expression of innate response cytokines CD14, TNF-α, IL-6, and SOCS3 as well as chemokines CCL2 and the CCL3 receptor CCR5. iPLA2β deficiency in response to ConA-induced AIH caused a significant decrease in hepatic and biliary bile acids, and this was associated with suppression of hepatic Cyp7A1, Ntcp and ABCB11/Bsep and upregulation of intestinal FXR/FGF15 mRNA expression. The suppression of hepatic Ntcp expression together with the loss of intestinal barrier could account for the observed bile acid leakage into peripheral blood. Thus, enteropathy may result from acute AIH in a susceptible host such as iPLA2β deficiency.

Genetic deletion of Mst1 alters T cell function and protects against autoimmunity

Mammalian sterile 20-like kinase 1 (Mst1) is a MAPK kinase kinase kinase which is involved in a wide range of cellular responses, including apoptosis, lymphocyte adhesion and trafficking. The contribution of Mst1 to Ag-specific immune responses and autoimmunity has not been well defined. In this study, we provide evidence for the essential role of Mst1 in T cell differentiation and autoimmunity, using both genetic and pharmacologic approaches. Absence of Mst1 in mice reduced T cell proliferation and IL-2 production in vitro, blocked cell cycle progression, and elevated activation-induced cell death in Th1 cells. Mst1 deficiency led to a CD4⁺ T cell development path that was biased toward Th2 and immunoregulatory cytokine production with suppressed Th1 responses. In addition, Mst1^−/− B cells showed decreased stimulation to B cell mitogens in vitro and deficient Ag-specific Ig production in vivo. Consistent with altered lymphocyte function, deletion of Mst1 reduced the severity of experimental autoimmune encephalomyelitis (EAE) and protected against collagen-induced arthritis development. Mst1^−/− CD4⁺ T cells displayed an intrinsic defect in their ability to respond to encephalitogenic antigens and deletion of Mst1 in the CD4⁺ T cell compartment was sufficient to alleviate CNS inflammation during EAE. These findings have prompted the discovery of novel compounds that are potent inhibitors of Mst1 and exhibit desirable pharmacokinetic properties. In conclusion, this report implicates Mst1 as a critical regulator of adaptive immune responses, Th1/Th2-dependent cytokine production, and as a potential therapeutic target for immune disorders.

Characterization of endocannabinoid-mediated induction of myeloid-derived suppressor cells involving mast cells and MCP-1

Endocannabinoids are lipid-signaling molecules found in the nervous system; however, their precise role in the periphery is unclear. In the current study, we observed that a single i.p. administration of AEA caused rapid induction of MDSCs. The MDSCs contained a mixture of granulocytic and monocytic subtypes and expressed Arg-1 and iNOS. The MDSCs suppressed T cell proliferation in vitro and used iNOS to mediate their effect. Moreover, adoptive transfer of MDSCs led to suppression of mBSA-induced DTH. Through the use of pharmacological inhibition, as well as genetic knockout mice, we found that the induction of MDSCs by AEA was CB1-dependent. The induction of MDSCs by AEA was reduced significantly in mast cell-deficient mice, while maintained in LPS-insensitive mice, showing that the induction of MDSCs by AEA was dependent, at least in part, on mast cells and independent of TLR4. Chemokine analysis of AEA- treated WT mice showed an early spike of MCP-1, which was decreased in Kit(W/W-sh) mice, showing a role of mast cells in the secretion of MCP-1 in response to AEA. Also, use of antibodies against MCP-1 or mice deficient in MCP-1 confirmed the role played by MCP-1. Interestingly, MCP-1 played a significant role in the induction of monocytic but not granulocytic MDSCs. Our studies demonstrate for the first time that endocannaboinids activate CB1 on mast cells to induce MCP-1, which facilitates recruitment of monocytic MDSCs.

Ethanol plus the Jo2 Fas agonistic antibody-induced liver injury is attenuated in mice with partial ablation of argininosuccinate synthase

BACKGROUND

Argininosuccinate synthase (ASS) is an enzyme shared by the urea cycle and the l-citrulline/nitric oxide (NO·) cycle. ASS is the rate-limiting enzyme in the urea cycle and along with nitric oxide synthase 2 (NOS2), it endows cells with the l-citrulline/NO· salvage pathway to continuously supply l-arginine from l-citrulline for sustained NO· generation. Thus, ASS conditions NO· synthesis by NOS2. Because of the relevance of NOS2 activation for liver injury, we examined the contribution of ASS to NO· generation and how it impacts liver injury.

METHODS

Wild-type (WT) mice and Ass(+/-) mice (Ass(-/-) mice are lethal) were intraperitoneally injected with ethanol (EtOH) at a dose of 2.5 g/kg of body weight twice a day for 3 days. Two hours after the last dose of EtOH, mice were administered the agonistic Jo2 anti-mouse Fas monoclonal antibody (Ab) at a dose of 0.2 μg/g of body weight. Mice were sacrificed 8 hours after the Jo2 Ab injection. Markers of nitrosative and oxidative stress as well as liver damage were analyzed.

RESULTS

EtOH plus Jo2 injection induced liver injury as shown by serum alanine aminotransferase and aspartate aminotransferase activity, liver pathology, TUNEL, and cleaved caspase-3 were lower in Ass(+/-) mice compared with WT mice, suggesting that ASS contributes to EtOH plus Jo2-mediated liver injury. CYP2E1 induction, glutathione depletion, and elevated thiobarbituric acid reactive substances were comparable in both groups of mice, suggesting that CYP2E1-mediated oxidative stress is not linked to ASS-induced liver injury. In contrast, NOS2 induction, 3-nitrotyrosine adducts formation and elevated nitrites, nitrates, and S-nitrosothiols were higher in livers from WT mice than from Ass(+/-) mice.

CONCLUSION

Decreased nitrosative stress causes lower EtOH plus Jo2-induced liver injury in Ass(+/-) mice.

MTI-101 (cyclized HYD1) binds a CD44 containing complex and induces necrotic cell death in multiple myeloma

Our laboratory recently reported that treatment with the d-amino acid containing peptide HYD1 induces necrotic cell death in multiple myeloma cell lines. Because of the intriguing biological activity and promising in vivo activity of HYD1, we pursued strategies for increasing the therapeutic efficacy of the linear peptide. These efforts led to a cyclized peptidomimetic, MTI-101, with increased in vitro activity and robust in vivo activity as a single agent using two myeloma models that consider the bone marrow microenvironment. MTI-101 treatment similar to HYD1 induced reactive oxygen species, depleted ATP levels, and failed to activate caspase-3. Moreover, MTI-101 is cross-resistant in H929 cells selected for acquired resistance to HYD1. Here, we pursued an unbiased chemical biology approach using biotinylated peptide affinity purification and liquid chromatography/tandem mass spectrometry analysis to identify binding partners of MTI-101. Using this approach, CD44 was identified as a predominant binding partner. Reducing the expression of CD44 was sufficient to induce cell death in multiple myeloma cell lines, indicating that multiple myeloma cells require CD44 expression for survival. Ectopic expression of CD44s correlated with increased binding of the FAM-conjugated peptide. However, ectopic expression of CD44s was not sufficient to increase the sensitivity to MTI-101-induced cell death. Mechanistically, we show that MTI-101-induced cell death occurs via a Rip1-, Rip3-, or Drp1-dependent and -independent pathway. Finally, we show that MTI-101 has robust activity as a single agent in the SCID-Hu bone implant and 5TGM1 in vivo model of multiple myeloma.

CD44 gene polymorphisms in breast cancer risk and prognosis: a study in North Indian population

Background

Cell surface biomarker CD44 plays an important role in breast cancer cell growth, differentiation, invasion, angiogenesis and tumour metastasis. Therefore, we aimed to investigate the role of CD44 gene polymorphisms in breast cancer risk and prognosis in North Indian population.

Materials & Methods

A total of 258 breast cancer patients and 241 healthy controls were included in the case-control study for risk prediction. According to RECIST, 114 patients who received neo-adjuvant chemotherapy were recruited for the evaluation of breast cancer prognosis. We examined the association of tagging SNP (rs353639) of Hapmap Gujrati Indians in Houston (GIH population) in CD44 gene along with a significant reported SNP (rs13347) in Chinese population by genotyping using Taqman allelic discrimination assays. Statistical analysis was done using SPSS software, version 17. In-silico analysis for prediction of functional effects was done using F-SNP and FAST-SNP.

Results

No significant association of both the genetic variants of the CD44 gene polymorphisms was found with breast cancer risk. On performing univariate analysis with clinicopathological characteristics and treatment response, we found significant association of genotype (CT+TT) of rs13347 polymorphism with earlier age of onset (P = 0.029, OR = 0.037). However, significance was lost in multivariate analysis. For rs353639 polymorphism, significant association was seen with clinical tumour size, both at the genotypic (AC+CC) (P = 0.039, OR = 3.02) as well as the allelic (C) (P = 0.042, OR = 2.87) levels. On performing multivariate analysis, increased significance of variant genotype (P = 0.017, OR = 4.29) and allele (P = 0.025, OR = 3.34) of rs353639 was found with clinical tumour size. In-silico analysis using F-SNP, showed altered transcriptional regulation for rs353639 polymorphism.

Conclusions

These findings suggest that CD44 rs353639 genetic variants may have significant effect in breast cancer prognosis. However, both the polymorphisms- rs13347 and rs353639 had no effect on breast cancer susceptibility.

Baicalein selectively induces apoptosis in activated lymphocytes and ameliorates concanavalin a-induced hepatitis in mice

Background

Insufficient apoptosis in activated lymphocytes contributes to the development of autoimmune hepatitis (AIH). Baicalein (BE), a flavonoid originally isolated from the root of Scutellaria baicalensis Georgi, possesses anti-inflammatory properties. However, whether BE can selectively induce apoptosis in activated lymphocytes and exert therapeutic effect on AIH has not been studied.

Methodology/Principal Findings

The pro-apoptotic properties of BE were evaluated in vitro on different types of immune cells, and in vivo effects of BE were examined in a murine model of Concanavalin A (Con A)-induced hepatitis. In vitro treatment with BE resulted in a higher increase in the level of apoptosis in Con A-stimulated murine splenocytes, Con A-stimulated CD3⁺ splenocytes, lipopolysaccharide (LPS)-stimulated CD19⁺ splenocytes, and phorbol 12-myristate 13-acetate/ionomycin-stimulated Jurkat T cells, compared with that in unstimulated naïve ones. Murine bone marrow-derived dentritic cells, peritoneal macrophages, and RAW264.7 cells, either stimulated with LPS or unstimulated, were all insensitive to the BE-induced apoptosis. BE treatment also led to a loss of mitochondrial membrane potential, an increase of cytochrome c release from mitochondria to the cytosol, a decrease in the ratio of Bcl-2/Bax, and activation of caspase-9,-3 in Con A-stimulated CD3⁺ splenocytes and LPS-stimulated CD19⁺ splenocytes, while showing no impact on Fas/FasL expressions and caspase-8 activation. In vivo administration of BE alleviated Con A-induced liver injury, suppressed serum level of TNF-α and IFN-γ, and reduced liver infiltration of mononuclear cells (MNCs). Furthermore, BE treatment increased the incidences of apoptosis in liver-infiltrating MNCs and splenocytes, as well as in CD3⁺ and CD19⁺ splenocytes. When liver MNCs and splenocytes from BE-treated mice were cultured in vitro for 24 h, they exhibited marked increase in apoptosis compared to vehicle-treated control.

Conclusions/Significance

The present study demonstrates the ability of BE to promote apoptosis in activated lymphocytes through mitochondrial pathway and its potential use in the treatment of AIH.

T-cell apoptosis induced by intratumoral activated hepatic stellate cells is associated with lung metastasis in hepatocellular carcinoma

Profound T cell inhibitory activity of hepatic stellate cells (HSCs) in vitro has recently been described in hepatocellular carcinoma (HCC). In the present study, we investigated the immune inhibitory activity of HSCs in vivo in an orthotopic rat HCC model with lung metastasis. Rats (n=24) were randomly sacrificed on days 7, 14, 21 and 28 (n=4 each). Lung tissues were stained with hematoxylin and eosin. Liver sections were stained for immunofluorescence analysis. T-cell apoptosis was detected using double staining for terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL). Staining revealed marked and continuous accumulation of α-smooth muscle actin with tumor progression after orthotopic tumor implantation in rat liver. T lymphocyte numbers gradually increased following tumor progression, and subset analysis revealed an increase in the distribution of liver CD8+ and CD4+ T cells. Double staining for CD3 and TUNEL demonstrated T-cell apoptosis. Apoptotic T cells were more frequent in the HCC livers compared to the normal livers, and were spatially associated with intratumoral activated HSCs (tHSCs), suggesting a direct interaction. T-cell apoptosis was more frequently induced in the co-cultures of activated splenic T cells(aT)/tHSCs compared to aT/quiescent (q) HSCs or qT/tHSCs. tHSCs were positively correlated with T-cell apoptosis, and the percentage of T-cells undergoing apoptosis was positively correlated with the number of lung metastasis nodules. T-cell apoptosis may be promoted via an interaction with tHSCs, suggesting that tHSCs regulate T cells and contribute to lung metastasis in HCC.

Liver sinusoidal endothelial cell lectin inhibits CTL-dependent virus clearance in mouse models of viral hepatitis

Liver sinusoidal endothelial cell lectin (LSECtin) was recently reported to suppress intrahepatic T cell immunity and to limit immune-mediated liver injury. However, its role in the outcome and pathogenesis of viral infection has not yet been elucidated. Using a mouse model infected with a hepatotropic adenovirus, we found that the absence of LSECtin led to a higher frequency of intrahepatic effector CTLs. These cells produced higher levels of antiviral cytokines and cytotoxic factors and exhibited an increased expression of the transcription factors T-bet and Runx3. This phenotype observed in the LSECtin-knockout cells mediated a more efficient virus-specific cytotoxicity compared with that of wild-type cells. As a consequence, LSECtin deficiency significantly accelerated liver adenovirus clearance. In contrast, LSECtin upregulation in the liver delayed viral clearance; this delayed clearance was accompanied by the downregulation of the antiviral activity of CTLs. We further constructed an immunocompetent mouse model of acute hepatitis B viral infection to demonstrate that LSECtin significantly delayed the clearance of hepatitis B virus from blood and infected hepatocytes by limiting the frequency of hepatitis B virus-specific IFN-γ-producing cells. Consistent with this function, LSECtin was upregulated in the liver of mouse models of viral hepatitis. Taken together, our results suggest that LSECtin may facilitate the reduction of liver inflammation at the cost of delaying virus clearance and that this effect might be hijacked by the virus as an escape mechanism.

MicroRNA let-7e is associated with the pathogenesis of experimental autoimmune encephalomyelitis

MicroRNAs (miRNAs) play important roles in the regulation of immune responses. There is evidence that miRNAs also participate in the pathogenesis of multiple sclerosis (MS), but how the miRNAs regulate the pathogenesis of MS is still under investigation. The identification of new members of the miRNA family associated with the pathogenesis of MS could facilitate early diagnosis and treatment. Here, we show that the level of miRNA let-7e is significantly upregulated in EAE, an animal model of MS using miRNA array and quantitative real-time PCR. The expression of let-7e was mainly in CD4(+) T cells and infiltrated mononuclear cells of CNS, and highly correlated with the development of EAE. We found that let-7e silencing in vivo inhibited encephalitogenic Th1 and Th17 cells and attenuated EAE, with reciprocal increase of Th2 cells; overexpression of let-7e enhanced Th1 and Th17 cells and aggravated EAE. We also identified IL-10 as one of the functional targets of let-7e. Together, we propose that let-7e is a new miRNA involved in the regulation of encephalitogenic T-cell differentiation and the pathogenesis of EAE.

The role of hyaluronan and the extracellular matrix in islet inflammation and immune regulation

Type 1 diabetes (T1D) is a disease that in most individuals results from autoimmune attack of a single tissue type, the pancreatic islet. A fundamental, unanswered question in T1D pathogenesis is how the islet tissue environment influences immune regulation. This crosstalk is likely to be communicated through the extracellular matrix (ECM). Here, we review what is known about the ECM in insulitis and examine how the tissue environment is synchronized with immune regulation. In particular, we focus on the role of hyaluronan (HA) and its interactions with Foxp3+ regulatory T-cells (Treg). We propose that HA is a "keystone molecule" in the inflammatory milieu and that HA, together with its associated binding proteins and receptors, is an appropriate point of entry for investigations into how ECM influences immune regulation in the islet.

Retinoic acid alleviates Con A-induced hepatitis and differentially regulates effector production in NKT cells

Retinoic acid (RA) is a diverse regulator of immune responses. Although RA promotes natural killer T (NKT) cell activation in vitro by increasing CD1d expression on antigen-presenting cells (APCs), the direct effects of RA on NKT-cell responses in vivo are not known. In the present study, we demonstrated the effect of RA on the severity of Con A-induced hepatitis and molecular changes of NKT cells. First, we demonstrated that Con A-induced liver damage was ameliorated by RA. In correlation with cytokine levels in serum, RA regulated the production of IFN-γ and IL-4 but not TNF-α by NKT cells without influencing the NKT-cell activation status. However, RA did not alleviate α-GalCer-induced liver injury, even though it reduced IFN-γ and IL-4 but not TNF-α levels in serum. This regulation was also detected when liver mononuclear cells (MNCs) or NKT hybridoma cells were treated with RA in vitro. The regulatory effect of RA on NKT cells was mediated by RAR-α, and RA reduced the phosphorylation of MAPK. These results suggest that RA differentially modulates the production of effector cytokines by NKT cells in hepatitis, and the suppressive effect of RA on hepatitis varies with the pathogenic mechanism of liver injury.

Hyaluronic acid receptor CD44 deficiency is associated with decreased Cryptococcus neoformans brain infection

Cryptococcus neoformans is a pathogenic yeast that can invade the brain and cause meningoencephalitis. Our previous in vitro studies suggested that the interaction between C. neoformans hyaluronic acid and human brain endothelial CD44 could be the initial step of brain invasion. In this report, we used a CD44 knock-out (KO or CD44(-/-)) mouse model to explore the importance of CD44 in C. neoformans brain invasion. Our results showed that C. neoformans-infected CD44 KO mice survived longer than the infected wild-type mice. Consistent with our in vitro results, the brain and cerebrospinal fluid fungal burden was reduced in CD44-deficient mice. Histopathological studies showed smaller and fewer cystic lesions in the brains of CD44 KO mice. Interestingly, the cystic lesions contained C. neoformans cells embedded within their polysaccharide capsule and were surrounded by host glial cells. We also found that a secondary hyaluronic acid receptor, RHAMM (receptor of hyaluronan-mediated motility), was present in the CD44 KO mice. Importantly, our studies demonstrated an in vivo blocking effect of simvastatin. These results suggest that the CD44 and RHAMM receptors function on membrane lipid rafts during invasion and that simvastatin may have a potential therapeutic role in C. neoformans infections of the brain.

Regulation of Antigen-Experienced T Cells: Lessons from the Quintessential Memory Marker CD44

Despite the widespread use of the cell-surface receptor CD44 as a marker for antigen (Ag)-experienced, effector and memory T cells, surprisingly little is known regarding its function on these cells. The best-established function of CD44 is the regulation of cell adhesion and migration. As such, the interactions of CD44, primarily with its major ligand, the extracellular matrix (ECM) component hyaluronic acid (HA), can be crucial for the recruitment and function of effector and memory T cells into/within inflamed tissues. However, little is known about the signaling events following engagement of CD44 on T cells and how cooperative interactions of CD44 with other surface receptors affect T cell responses. Recent evidence suggests that the CD44 signaling pathway(s) may be shared with those of other adhesion receptors, and that these provide contextual signals at different anatomical sites to ensure the correct T cell effector responses. Furthermore, CD44 ligation may augment T cell activation after Ag encounter and promote T cell survival, as well as contribute to regulation of the contraction phase of an immune response and the maintenance of tolerance. Once the memory phase is established, CD44 may have a role in ensuring the functional fitness of memory T cells. Thus, the summation of potential signals after CD44 ligation on T cells highlights that migration and adhesion to the ECM can critically impact the development and homeostasis of memory T cells, and may differentially affect subsets of T cells. These aspects of CD44 biology on T cells and how they might be modulated for translational purposes are discussed.

Activated lymphocytes and high liver expression of IFN-γ are associated with fulminant hepatic failure in patients

BACKGROUND & AIMS

To study immunological mechanisms of fulminant hepatic failure (FHF) derived from extensive liver lesions, 14 patients with FHF induced by different aetiologies were investigated by observance of both lymphocyte phenotyping and cytokine levels.

METHODS

Five patients bearing benign acute hepatitis B (AHB) and seven healthy liver donors (HC) were used as controls. Samples of liver and blood from both FHF patients and HC were obtained during transplantation procedures. Plasma levels of IL-1β, IL-4, IL-6, IL-8, IL-10, IFN-γ, TNF-α, MCP-1, RANTES and MIP-1α were quantified using a multiplex immunoassay. Cell characterization was carried out by flow cytometry. IFN-γ staining was performed on liver sections using immunofluorescence methods.

RESULTS

An increase of peripheral frequency of natural killer (NK) cells expressing early activation markers (CD69, HLA-DR and CD38) and adhesion molecule CD44 was observed in FHF patients. Elevated frequency of T lymphocytes CD4(+) and CD8(+) expressing CD38 and adhesion molecules CD29 and CD44 was also observed in FHF. Additionally, an increase of natural killer T cells (NKT) was detected in FHF patients. High plasma cytokine levels were not statistically different between FHF and AHB patients. In comparison to HC, a strong liver expression of IFN-γ was detected in FHF patients. The increased frequency of CD4(+) CD44(+) and IL-8 cytokine was found in patients with poor prognosis.

CONCLUSIONS

These findings indicate the involvement of NK and NKT cells as well as T lymphocytes CD4(+) and CD8(+) in the inflammatory process inducing FHF, confirmed by the high hepatic expression of IFN-γ.

CD44 Reciprocally regulates the differentiation of encephalitogenic Th1/Th17 and Th2/regulatory T cells through epigenetic modulation involving DNA methylation of cytokine gene promoters, thereby controlling the development of experimental autoimmune encephalomyelitis

CD44 is expressed by a variety of cells, including glial and T cells. Furthermore, in the demyelinating lesions of multiple sclerosis, CD44 expression is chronically elevated. In this study, we demonstrate that targeted deletion of CD44 attenuated myelin oligodendrocyte glycoprotein peptide-induced experimental autoimmune encephalitomyelitis (EAE) through novel regulatory mechanisms affecting Th differentiation. Specifically, by developing chimeras and using adoptive transfer experiments, we noted that CD44 deficiency on CD4(+) T cells, but not other cells, conferred protection against EAE induction. CD44 expression played a crucial role in Th differentiation, inasmuch as deletion of CD44 inhibited Th1/Th17 differentiation while simultaneously enhancing Th2/regulatory T cell differentiation. In contrast, expression of CD44 promoted Th1/Th17 differentiation. When osteopontin and hyaluronic acid, the two major ligands of CD44, were tested for their role in Th differentiation, osteopontin, but not hyaluronic acid, promoted Th1/Th17 differentiation. Furthermore, activation of CD44(+) encephalitogenic T cells with myelin oligodendrocyte glycoprotein peptide led to demethylation at the ifnγ/il17a promoter region while displaying hypermethylation at the il4/foxp3 gene promoter. Interestingly, similar activation of CD44-deficient encephalitogenic T cells led to increased hypermethylation of ifnγ/il17a gene and marked demethylation of il4/foxp3 gene promoter. Together, these data suggested that signaling through CD44, in encephalitogenic T cells, plays a crucial role in the differentiation of Th cells through epigenetic regulation, specifically DNA methylation of Th1/Th17 and Th2 cytokine genes. The current study also suggests that molecular targeting of CD44 receptor to promote a switch from Th1/Th17 to Th2/regulatory T cell differentiation may provide a novel treatment modality against EAE.

Role of myeloid-derived suppressor cells in amelioration of experimental autoimmune hepatitis following activation of TRPV1 receptors by cannabidiol. PLoS One. 2011;6:e18281. [PMID: 21483776 PMCID: PMC3069975 DOI: 10.1371/journal.pone.0018281]

Background

Myeloid-derived suppressor cells (MDSCs) are getting increased attention as one of the main regulatory cells of the immune system. They are induced at sites of inflammation and can potently suppress T cell functions. In the current study, we demonstrate how activation of TRPV1 vanilloid receptors can trigger MDSCs, which in turn, can inhibit inflammation and hepatitis.

Methodology/Principal Findings

Polyclonal activation of T cells, following injection of concanavalin A (ConA), in C57BL/6 mice caused acute hepatitis, characterized by significant increase in aspartate transaminase (AST), induction of inflammatory cytokines, and infiltration of mononuclear cells in the liver, leading to severe liver injury. Administration of cannabidiol (CBD), a natural non-psychoactive cannabinoid, after ConA challenge, inhibited hepatitis in a dose-dependent manner, along with all of the associated inflammation markers. Phenotypic analysis of liver infiltrating cells showed that CBD-mediated suppression of hepatitis was associated with increased induction of arginase-expressing CD11b⁺Gr-1⁺ MDSCs. Purified CBD-induced MDSCs could effectively suppress T cell proliferation in vitro in arginase-dependent manner. Furthermore, adoptive transfer of purified MDSCs into naïve mice conferred significant protection from ConA-induced hepatitis. CBD failed to induce MDSCs and suppress hepatitis in the livers of vanilloid receptor-deficient mice (TRPV1^−/−) thereby suggesting that CBD primarily acted via this receptor to induce MDSCs and suppress hepatitis. While MDSCs induced by CBD in liver consisted of granulocytic and monocytic subsets at a ratio of ∼2∶1, the monocytic MDSCs were more immunosuppressive compared to granulocytic MDSCs. The ability of CBD to induce MDSCs and suppress hepatitis was also demonstrable in Staphylococcal enterotoxin B-induced liver injury.

Conclusions/Significance

This study demonstrates for the first time that MDSCs play a critical role in attenuating acute inflammation in the liver, and that agents such as CBD, which trigger MDSCs through activation of TRPV1 vanilloid receptors may constitute a novel therapeutic modality to treat inflammatory diseases.

Hyaluronan as an immune regulator in human diseases

Accumulation and turnover of extracellular matrix components are the hallmarks of tissue injury. Fragmented hyaluronan stimulates the expression of inflammatory genes by a variety of immune cells at the injury site. Hyaluronan binds to a number of cell surface proteins on various cell types. Hyaluronan fragments signal through both Toll-like receptor (TLR) 4 and TLR2 as well as CD44 to stimulate inflammatory genes in inflammatory cells. Hyaluronan is also present on the cell surface of epithelial cells and provides protection against tissue damage from the environment by interacting with TLR2 and TLR4. Hyaluronan and hyaluronan-binding proteins regulate inflammation, tissue injury, and repair through regulating inflammatory cell recruitment, release of inflammatory cytokines, and cell migration. This review focuses on the role of hyaluronan as an immune regulator in human diseases.

The bile acid sensor farnesoid X receptor is a modulator of liver immunity in a rodent model of acute hepatitis

Immune-mediated liver diseases including autoimmune and viral hepatitis are a major health problem worldwide. In this study, we report that activation of the farnesoid X receptor (FXR), a member of the ligand-activated nuclear receptor superfamily and bile sensor highly expressed in the liver, attenuates liver injury in a model of autoimmune hepatitis induced by Con A. We found that FXR gene ablation results in a time-dependent increase of liver expression (up to 20-fold in a 9-mo-old mouse) of osteopontin, a NKT cell-derived extracellular matrix protein and immunoregulatory cytokine. In comparison to wild-type, FXR(-/-) mice are more susceptible to Con A-induced hepatitis and react to Con A administration by an unregulated production of osteopontin. Administering wild-type mice with a synthetic FXR agonist attenuated Con A-induced liver damage and liver expression of the osteopontin gene. By in vitro studies, we found that FXR is expressed by primarily isolated NKT cells and its ablation favors ostepontin production in response to Con A. Chromatin immunoprecipitation assay and coimmunoprecipitation experiments demonstrate that the short heterodimer partner (SHP), a nuclear receptor and FXR target, was expressed by NKT cell hybridomas and increased in response to FXR activation. FXR activates SHP that interacts with and inhibits c-Jun binding to the osteopontin promoter. These data indicate that in NKT cells, FXR activation causes a SHP-mediated inhibition of osteopontin production. These data support the notion that the bile acid sensor FXR regulates the activation of liver NKT cells.

Chronic ethanol feeding potentiates Fas Jo2-induced hepatotoxicity: role of CYP2E1 and TNF-alpha and activation of JNK and P38 MAP kinase

We have previously shown that treatment of mice with pyrazole or acute ethanol potentiated Fas agonistic Jo2 antibody-induced liver injury by a mechanism involving induction of CYP2E1 and elevated oxidative stress. The current study evaluated whether chronic alcohol feeding potentiates Fas-induced liver injury and whether CYP2E1 plays a role in any enhanced hepatotoxicity. Wild-type and CYP2E1 knockout mice were fed ethanol or isocaloric dextrose for 4 weeks followed by a single treatment with either saline or Jo2. Mice were killed 8 h after the Jo2 challenge. There were three- to five fold increases in transaminases and more extensive eosinophilic necrosis, hemorrhage, and infiltration of inflammatory cells in the central zone of the hepatic lobule in the ethanol-fed mice treated with Jo2 compared to the dextrose/Jo2- or ethanol/saline-treated mice. Liver injury was blunted in ethanol-fed CYP2E1 knockout mice treated with Jo2. The chronic ethanol feeding produced steatosis, elevation of CYP2E1, and oxidative stress in wild-type but not CYP2E1 knockout mice. These changes in wild-type mice fed ethanol were similar after saline or Jo2 treatment. The Jo2 treatment produced activation of JNK and P38 MAP kinase, increased activity of caspase-8 and -3, and lowered hepatic GSH levels in both the dextrose- and the alcohol-fed mice. JNK was activated at early times after Jo2 treatment in the ethanol-fed mice. Serum TNF-alpha levels were strikingly elevated in the wild-type ethanol/Jo2 group, which showed liver injury, compared to all the other groups, which did not show liver injury. Inhibition of JNK or P38 MAPK partially, but not completely, prevented the elevated liver injury in the wild-type ethanol/Jo2 mice. These results show that chronic ethanol feeding enhances Fas-induced liver injury by a mechanism associated with induction of CYP2E1, elevated serum TNF-alpha levels, and activation of MAPK.

Role of CD44 in the differentiation of Th1 and Th2 cells: CD44-deficiency enhances the development of Th2 effectors in response to sheep RBC and chicken ovalbumin

CD4 T cells can be primarily polarized to differentiate into Th1 or Th2 cells. CD44 is a marker of T cell activation and a property of long-lived memory cells and implicated in cell migration, activation, and differentiation. To date, whether CD44 has a role in regulating Th1-Th2 differentiation has not been determined. In this study, we compared Th1 and Th2 responses in wild-type and CD44-deficient mice in response to sheep RBC and chicken OVA, as well as examined Th1-Th2 differentiation in vivo and in vitro from CD44-sufficient and CD44-deficient naive CD4 T cells. We observed that deficiency of CD44 tended to inhibit Th1 while promoting Th2 differentiation. Furthermore, chimeric studies suggested that CD44 expression by CD4 T cells was essential for such Th2 bias. The regulation by CD44 occurred at the transcription level leading to up-regulated GATA3 and down-regulated T-bet expression in activated CD4 T cells. We also noted that CD44-deficiency could modify the state of dendritic cell subsets to induce a Th2-biased development. Results presented in this study demonstrate for the first time that CD44 participates in the regulation of Th1-Th2 differentiation.

Many checkpoints on the road to cell death: regulation of Fas-FasL interactions and Fas signaling in peripheral immune responses

Interactions between the TNF-family receptor Fas (CD95) and Fas Ligand (FasL, CD178) can efficiently induce apoptosis and are critical for the maintenance of immunological self-tolerance. FasL is kept under strict control by transcriptional and posttranslational regulation. Surface FasL can be cleaved by metalloproteases, resulting in shed extracellular domains, and FasL can also traffic to secretory lysosomes. Each form of FasL has distinct biological functions. Fas is more ubiquitously expressed, but its apoptosis-inducing function is regulated by a number of mechanisms including submembrane localization, efficiency of receptor signaling complex assembly and activation, and bcl-2 family members in some circumstances. When apoptosis is not induced, Fas-FasL interactions can also trigger a number of activating and proinflammatory signals. Harnessing the apoptosis-inducing potential of Fas for therapy of cancer and autoimmune disease has been actively pursued, and despite a number of unexpected side-effects that result from manipulating Fas-FasL interactions, this remains a worthy goal.

Hyaluronan induces cell death in activated T cells through CD44

In the immune system, leukocyte activation induces CD44 to bind hyaluronan, a component of the extracellular matrix. Here we used gain and loss of hyaluronan-binding mutants of CD44 to examine the consequence of hyaluronan binding in T cells. Jurkat T cells transfected with CD44 mutated at S180, which prevented the addition of chondroitin sulfate, displayed constitutively high levels of hyaluronan binding. These cells were more susceptible to activation-induced cell death, whereas cells expressing a CD44 mutant unable to bind hyaluronan (R41A) were resistant to cell death. In TCR or PMA activated Jurkat T cells, hyaluronan induced rapid cell death. This depended on the level of hyaluronan binding by the cell, and the amount and size of hyaluronan. High molecular mass hyaluronan had the greatest effect and cell death occurred independently of Fas and caspase activation. In splenic T cells, high hyaluronan binding occurred in a subpopulation of cells undergoing activation-induced cell death. In addition, hyaluronan induced cell death in approximately 10% of reactivated splenic T cells when Fas-dependent apoptosis was prevented by Ab blocking or in Fas negative MRL/lpr T cells. This demonstrates that hyaluronan can induce cell death in activated, high hyaluronan binding T cells via a Fas-independent mechanism.

Critical role of CD44 in hepatotoxin-mediated liver injury

BACKGROUND/AIMS

Blocking of adhesion molecules is considered to be one of the therapeutic strategies inflammatory diseases, although it remains unclear whether this strategy is beneficial.

METHODS

We used CD44-deficient mice to assess whether inhibition of CD44 could control liver injury caused by carbon tetrachloride (CCl(4)).

RESULTS

CD44-deficient mice exhibited suppressed liver inflammation during the early phase (within 6h) after CCl(4) injection due to reduced inflammatory cell infiltration and cytokine production, but showed severe liver inflammation with increased numbers of apoptotic hepatocytes at the late phase (after 12h). The induction of hepatocyte apoptosis was triggered by reduced NF-kappaB activity, which was induced by the low inflammatory cytokine concentrations. Furthermore, macrophages contributed to the induction of hepatocyte apoptosis, since neutralization by an anti-CD11b antibody significantly protected against hepatocyte apoptosis. Finally, we found that blocking of MIP-2 and TNF-alpha reduced hepatocyte apoptosis with decreased numbers of intrahepatic leukocytes and reduced inflammatory cytokine production.

CONCLUSIONS

These findings suggest that targeting of CD44 as a therapeutic approach for inflammatory liver diseases may require caution for particular immune systems in the liver.

Small changes in lymphocyte development and activation in mice through tissue-specific alteration of heparan sulphate

We have examined the role of heparan sulphate in lymphocyte development and activation in mice by conditionally deleting the genes encoding the heparan sulphate biosynthetic enzymes N-deacetylase/N-sulphotransferase-1 and -2 (Ndst1 and Ndst2) and glucuronic acid/N-acetylglucosamine co-polymerase-1 (Ext1) in T cells and B cells, respectively. Ndst1 and Ndst2 are the only Ndst isoforms in T cells. In T-cell Ndst-deficient mice there were normal ratios of CD4(+)/CD8(+) cells in the blood, spleen and thymus, indicating no dramatic effect on development. However, Ndst-deficient T cells were hyperresponsive to low-level activation, suggesting that cell surface heparan sulphate plays a role in T-cell proliferation. The hyperresponsive state correlated with a decrease in cell surface heparan sulphate that occurs in response to activation in wild-type cells. There was a slight change in the number of developing B cells in B-cell Ext1-deficient mice, but the alteration did not cause a change in antibody production. These findings demonstrate that cell surface heparan sulphate may not play a crucial role in lymphocyte development, but can modulate the sensitivity of T cells to activation.

Attenuation of experimental autoimmune hepatitis by exogenous and endogenous cannabinoids: involvement of regulatory T cells

Immune-mediated liver diseases including autoimmune and viral hepatitis are a major health problem worldwide. Natural cannabinoids such as Delta(9)-tetrahydrocannabinol (THC) effectively modulate immune cell function, and they have shown therapeutic potential in treating inflammatory diseases. We investigated the effects of THC in a murine model of concanavalin A (ConA)-induced hepatitis. Intraperitoneal administration of THC after ConA challenge inhibited hepatitis as shown by significant decrease in liver enzymes and reduced liver tissue injury. Furthermore, THC treatment resulted in significant suppression of crucial inflammatory cytokines in ConA-induced hepatitis. It is noteworthy that THC treatment in ConA-injected mice led to significant increase in absolute number of Forkhead helix transcription factor p3+ T regulatory cells in liver. We were surprised to find that select cannabinoid receptor (CB1 or CB2) agonists were not able to block hepatitis either independently or in combination. However, CB1/CB2 mixed agonists were able to efficiently attenuate hepatitis similar to THC. The modulatory effect of THC in ConA-induced hepatitis was reversed by both CB1 and CB2 antagonists. We also observed that endogenous cannabinoid anandamide was able to reduce hepatitis by suppressing cytokine levels. In addition, deficiency or inhibition of endocannabinoid hydrolyzing enzyme fatty acid amide hydrolase (FAAH), which leads to increased levels of endogenous cannabinoids, resulted in decreased liver injury upon ConA challenge. Our data demonstrate that targeting cannabinoid receptors using exogenous or endogenous cannabinoids and use of FAAH inhibitors may constitute novel therapeutic modalities to treat immune-mediated liver inflammation.

The CD44 standard/ezrin complex regulates Fas-mediated apoptosis in Jurkat cells

The transmembrane receptor CD44 conveys important signals from the extracellular microenvironment to the cytoplasm, a phenomena known as "outside-in" signaling. CD44 exists as several isoforms that result from alternative splicing, which differ only in the extracellular domain but yet exhibit different activities. CD44 is a binding partner for the membrane-cytoskeleton cross-linker protein ezrin. In this study, we demonstrate that only CD44 standard (CD44s) colocalizes and interacts with the actin cross-linkers ezrin and moesin using well-characterized cell lines engineered to express different CD44 isoforms. Importantly, we also show that the association CD44s-ezrin-actin is an important modulator of Fas-mediated apoptosis. The results highlight a mechanism by which signals from the extracellular milieu regulate intracellular signaling activities involved in programmed cell death.

Cutting edge: Rac GTPases sensitize activated T cells to die via Fas

In activated CD4(+) T cells, TCR restimulation triggers apoptosis that depends on interactions between the death receptor Fas and its ligand, FasL. This process, termed restimulation-induced cell death (RICD), is a mechanism of peripheral immune tolerance. TCR signaling sensitizes activated T cells to Fas-mediated apoptosis, but what pathways mediate this process are not known. In this study we identify the Rho GTPases Rac1 and Rac2 as essential components in restimulation-induced cell death. RNA interference-mediated knockdown of Rac GTPases greatly reduced Fas-dependent, TCR-induced apoptosis. The ability of Rac1 to sensitize T cells to Fas-induced apoptosis correlated with Rac-mediated cytoskeletal reorganization, dephosphorylation of the ERM (ezrin/radixin/moesin) family of cytoskeletal linker proteins, and the translocation of Fas to lipid raft microdomains. In primary activated CD4(+) T cells, Rac1 and Rac2 were independently required for maximal TCR-induced apoptosis. Activating Rac signaling may be a novel way to sensitize chronically stimulated lymphocytes to Fas-induced apoptosis, an important goal in the treatment of autoimmune diseases.

Engagement of CD44 up-regulates Fas ligand expression on T cells leading to activation-induced cell death

Activation-induced cell death (AICD) plays a pivotal role in self-tolerance by deleting autoreactive T cells, but a defect of AICD results in expansion of autoreactive T cells and is deeply involved in the pathogenesis of rheumatoid arthritis. Although the process of AICD is mainly mediated by Fas Ligand (FasL)/Fas signaling, it remains unclear what induces FasL expression on T cells. In the present study, we found that CD44 was the most potent stimulator of FasL expression on human peripheral T cells. CD44 cross-linking rapidly up-regulated FasL expression on the T cell surface by delivery from the cytoplasm without new FasL protein synthesis. This up-regulation of FasL was mediated by activation of a tyrosine kinase, IP3 receptor-dependent Ca(2+) mobilization and actin cytoskeletal rearrangements. Furthermore, AICD induced by CD3 restimulation was inhibited by hyaluronidase as well as by soluble Fas, indicating an interaction between membrane-bound hyaluronan and the cell surface CD44 was involved in the up-regulation of FasL expression on T cells and subsequent AICD. We therefore propose that the engagement of CD44 on T cells can eliminate autoreactive T cells by expression of FasL and FasL-mediated AICD.

Acute ethanol pretreatment increases FAS-mediated liver injury in mice: role of oxidative stress and CYP2E1-dependent and -independent pathways

This study evaluated whether acute ethanol pretreatment potentiates Fas-mediated liver injury and if oxidative stress and CYP2E1 play a role in any enhanced hepatotoxicity. There were 3-fold increases of transaminases and more extensive apoptotic necrosis of hepatocytes and focal hemorrhages of the hepatic lobule in mice treated with Jo2 Fas agonistic antibody plus ethanol compared to saline control or to mice treated with Jo2 or ethanol alone. CYP2E1 catalytic activity and protein were increased 2-fold by the acute ethanol pretreatment. There were 2- and 2.5-fold increases of caspase-8 and caspase-3 activity and 1.6-fold increases of apoptotic-positive cells in the Jo2 plus acute ethanol group compared to the Jo2 alone group. Levels of TNF-alpha, malondialdehyde, 4-hydroxynonenal, protein carbonyl formation, 3-nitrotyrosine protein adducts, and inducible nitric oxide synthase were increased in the Jo2 plus ethanol group. The enhanced hepatotoxicity of Jo2 plus ethanol and the elevated oxidative stress and TNF levels were lower in CYP2E1 knockout mice compared to wild-type mice expressing CYP2E1 but higher than saline controls. Toxicity also declined in mice treated with gadolinium chloride, an inhibitor of the inducible nitric oxide synthase or the antioxidant, N-acetyl-L-cysteine. These data indicate that acute ethanol pretreatment is capable of elevating hepatic apoptosis and liver injury induced by Jo2 Fas agonistic antibody. The enhanced hepatotoxicity involves increased oxidative and nitrosative stress, and appears to be mediated by CYP2E1-dependent and also CYP2E1-independent mechanisms.

Suppression of immune-mediated liver injury after vaccination with attenuated pathogenic cells

Cell vaccination via immunization with attenuated pathogenic cells is an effective preventive method that has been successfully applied in several animal models of inflammatory or autoimmune diseases. Concanavalin A (Con A)-induced hepatitis (CIH) is a commonly used experimental model to study immune-mediated liver injury. Multiple cell types including T lymphocytes, macrophages and neutrophils have been found to be involved in the pathogenesis of CIH. In this study, we used attenuated spleen lymphocytes or peripheral blood lymphocytes as vaccines to investigate whether they could induce protective immune responses to prevent mice from developing CIH. We found that mice receiving such vaccination before CIH induction developed much milder diseases, exhibited a lower level of alanine aminotransferase (ALT) released into their plasma and had less inflammatory lesions in their livers. Such CIH-suppression is dose- and frequency-dependent. The suppressive effect was associated with inhibition of several major inflammatory mediators, pro-inflammatory cytokines and chemokines.

Expression of extra trinucleotide in CD44 variant of rheumatoid arthritis patients allows generation of disease-specific monoclonal antibody

Selective targeting of cells engaged in pathological activities is a major challenge for medical research. We generated monoclonal antibodies (mAbs) that exclusively bind, at concentrations ranging from 2 to 100 microg/ml, to a modified CD44 variant (designated CD44vRA) expressed on synovial fluid cells from joints of rheumatoid arthritis (RA) patients. These mAbs cross-reacted with keratinocytes expressing wild type CD44vRA (CD44v3-v10) only at a relatively high concentration (200 microg/ml). Sequence analysis of CD44vRA cDNA revealed, in 33 out of 43 RA and psoriatic arthritis patients, an extra intron-derived trinucleotide, CAG, which allows translation of an extra alanine. This insertion imposes a configurational change on the cell surface CD44 of RA synovial fluid cells, creating an immunogenic epitope and potentiating the ability to produce disease-specific antibodies. Indeed, the anti-CD44vRA mAbs (designated F8:33) were able to induce apoptosis in synovial fluid cells from RA patients, but not in peripheral blood leukocytes from the same patients, in keratinocytes from normal donors or in synovial fluid cells from osteoarthritis patients. Furthermore, injection of anti-CD44vRA mAbs reduced joint inflammation in DBA/1 mice with collagen-induced arthritis. These findings show that anti-CD44vRA mAbs are both bioactive and RA-specific.

CD44 is the signaling component of the macrophage migration inhibitory factor-CD74 receptor complex

The macrophage migration inhibitory factor (MIF) receptor (CD74) was cloned recently, but the signaling mechanism is not evident. We hypothesized that signaling requires an additional molecule such as CD44, which activates nonreceptor tyrosine kinases. We utilized the CD74- and CD44-deficient COS-7/M6 cell to create stable transfectants expressing CD74, CD44, and a truncated CD44 lacking its intracytoplasmic signaling domain. CD74 alone mediated MIF binding; however, MIF-induced ERK1 and ERK2 kinase phosphorylation required the coexpression of full-length CD44. MIF binding was associated with the serine phosphorylation of CD74 and CD44. Investigations that used siRNA or kinase inhibitors indicate that MIF-induced ERK1 and ERK2 activation through CD44 required the Src tyrosine kinase. Studies of CD74, CD44, and CD74-CD44 transformants and corresponding mutant cells showed that CD74 and CD44 were necessary for MIF protection from apoptosis. These data establish CD44 as an integral member of the CD74 receptor complex leading to MIF signal transduction.

Delta9-tetrahydrocannabinol-induced apoptosis in Jurkat leukemia T cells is regulated by translocation of Bad to mitochondria

Plant-derived cannabinoids, including Delta9-tetrahydrocannabinol (THC), induce apoptosis in leukemic cells, although the precise mechanism remains unclear. In the current study, we investigated the effect of THC on the upstream and downstream events that modulate the extracellular signal-regulated kinase (ERK) module of mitogen-activated protein kinase pathways primarily in human Jurkat leukemia T cells. The data showed that THC down-regulated Raf-1/mitogen-activated protein kinase/ERK kinase (MEK)/ERK/RSK pathway leading to translocation of Bad to mitochondria. THC also decreased the phosphorylation of Akt. However, no significant association of Bad translocation with phosphatidylinositol 3-kinase/Akt and protein kinase A signaling pathways was noted when treated cells were examined in relation to phosphorylation status of Bad by Western blot and localization of Bad to mitochondria by confocal analysis. Furthermore, THC treatment decreased the Bad phosphorylation at Ser(112) but failed to alter the level of phospho-Bad on site Ser(136) that has been reported to be associated with phosphatidylinositol 3-kinase/Akt signal pathway. Jurkat cells expressing a constitutively active MEK construct were found to be resistant to THC-mediated apoptosis and failed to exhibit decreased phospho-Bad on Ser(112) as well as Bad translocation to mitochondria. Finally, use of Bad small interfering RNA reduced the expression of Bad in Jurkat cells leading to increased resistance to THC-mediated apoptosis. Together, these data suggested that Raf-1/MEK/ERK/RSK-mediated Bad translocation played a critical role in THC-induced apoptosis in Jurkat cells.

CD44 differentially activates mouse NK T cells and conventional T cells

NK T (NKT) cells are an important component of the innate immune system and recognize the MHC class I-like CD1d molecule. NKT cells possess significant immunoregulatory activity due to their rapid secretion of large quantities of pro- and anti-inflammatory cytokines following CD1d-dependent stimulation. Because the innate immune system is programmed to respond to a multitude of diverse stimuli and must be able to quickly differentiate between pathogenic and endogenous signals, we hypothesized that, apart from stimulation via the TCR (e.g., CD1d-dependent activation), there must be multiple activation pathways that can be triggered through other cell surface receptors on NKT cells. Therefore, we analyzed the ability of CD44, a structurally diverse cell surface receptor expressed on most cells, to stimulate murine NKT cells, compared with conventional T cells. Stimulation of CD44 through Ab cross-linking or binding to its natural ligands hyaluronan and osteopontin induced NKT cells to secrete cytokines, up-regulate activation markers, undergo morphological changes, and resist activation-induced cell death, whereas conventional T cells only exhibited changes in morphology and protection from activation-induced cell death. This CD44-specific stimulation of NKT cells correlated with their ability to bind hyaluronan. Thus, fundamental differences in CD44 function between these lymphocyte subsets suggest an important biological role for CD44 in the innate immune response.

SHAP potentiates the CD44-mediated leukocyte adhesion to the hyaluronan substratum

CD44-hyaluronan (HA) interaction is involved in diverse physiological and pathological processes. Regulation of interacting avidity is well studied on CD44 but rarely on HA. We discovered a unique covalent modification of HA with a protein, SHAP, that corresponds to the heavy chains of inter-alpha-trypsin inhibitor family molecules circulating in blood. Formation of the SHAP.HA complex is often associated with inflammation, a well known process involving the CD44-HA interaction. We therefore examined the effect of SHAP on the CD44-HA interaction-mediated lymphocyte adhesion. Under both static and flowing conditions, Hut78 cells (CD44-positive) and CD44-transfected Jurkat cells (originally CD44-negative) adhered preferentially to the immobilized SHAP.HA complex than to HA. The enhanced adhesion is exclusively mediated by the CD44-HA interaction, because it was inhibited by HA, but not IalphaI, and was completely abolished by pretreating the cells with anti-CD44 antibodies. SHAP appears to potentiate the interaction by increasing the avidity of HA to CD44 and altering their distribution on cell surfaces. Large amounts of the SHAP.HA complex accumulate in the hyperplastic synovium of rheumatoid arthritis patients. Leukocytes infiltrated to the synovium were strongly positive for HA, SHAP, and CD44 on their surfaces, suggesting a role for the adhesion-enhancing effect of SHAP in pathogenesis.

Mouse B cell activation is inhibited by CD44 cross-linking

Lymphocyte activation and trafficking are indispensable to the immune system. CD44 is an adhesion molecule with known importance in T cell activation, lymphocyte trafficking, and tumor metastasis. Although CD44 has been shown to participate in the activation, rolling and adhesion, and homing of T cells, the role of CD44 on B cells is relatively unknown. The effects of CD44 cross-linking on murine B cell activation via CD40L was explored using the anti-CD44 mAbs RK3G9 and IM7. When immobilized on a plate, both RK3G9 and IM7 were found to strongly inhibit B cell proliferation and Ig production, especially at lower cell input concentrations. IgE inhibition was especially prominent. In contrast, soluble RK3G9 added to the B cell cultures had no effect. The inhibitory effect of anti-CD44 on B cell activation was not influenced by the addition of the anti-FcgammaRII, indicating that Fc cross-linking did not play a role in this inhibition. As Ig production requires several days for both B cell proliferation and differentiation to occur, the effects of delayed addition of immobilized anti-CD44 mAbs were studied, and the results indicated no inhibition after 96 hrs of culture. Finally, B cells were activated by either LPS or anti-IgM F(ab')2. While LPS-induced B cell activation was inhibited by immobilized anti-CD44 mAbs, anti-IgM activation was refractory. Interestingly, addition of both anti-IgM and CD40L or LPS resulted in some modulation of the inhibitory activity. These results suggest that CD44 cross-linking could control polyclonal B cell activation by CD40L, but allow sIgM/CD40L activation to continue.

Rescue of in vivo FAS-induced apoptosis of hepatocytes by corticosteroids either associated with alcohol consumption by mice or provided exogenously

The pathogenic effects of many hepatic viral infections are mediated, at least in part, by the immune response to the infected hepatocyte. The immune response in the infected liver involves the interaction of cytotoxic T cells (CTL) with the hepatocytes through the interaction of FAS-ligand on the CTL and FAS on the hepatocyte. The initial hypothesis for this study was that alcohol consumption by mice would sensitize the liver to apoptosis induced by ligation of FAS. C57Bl/6 mice fed ethanol in a liquid diet did show an increased percentage of apoptotic cells 2 h after injection with anti-FAS as compared with the percentage in the control mice. However, 4 and 6 h after anti-FAS injection, control mice showed high percentages of apoptotic cells (20% to 41%) compared with 5% and 4% apoptotic cells in the ethanol-fed mice. The decreased apoptosis of ethanol-fed mice correlated closely with corticosterone levels in the sera. This was confirmed by the finding that adrenalectomized (ADX) mice provided a high level of corticosterone in drinking water were protected against FAS-induced hepatocyte apoptosis. Ethanol-fed mice showed a significant elevation of serum alanine aminotransferase (ALT) levels indicating the development of hepatitis in spite of the relatively low proportion of apoptotic cells in the liver. In conclusion, high levels of corticosterone protect hepatocytes from FAS-mediated apoptosis, but do not prevent the ultimate development of liver damage. In experiments where mice were provided ethanol chronically in drinking water, where stress is minimal, higher levels of ALT were noted in animals in the ethanol group as compared with animals in the control group. These data support the suggestion that ethanol increases hepatocyte sensitivity to FAS-mediated damage.

Lack of Chemokine Receptor CCR5 Promotes Murine Fulminant Liver Failure by Preventing the Apoptosis of Activated CD1d-Restricted NKT Cells

Fulminant liver failure (FLF) consists of a cascade of events beginning with a presumed uncontrolled systemic activation of the immune system. The etiology of FLF remains undefined. In this study, we demonstrate that CCR5 deficiency promotes the development of acute FLF in mice following Con A administration by preventing activated hepatic CD1d-restricted NKT cells (but not conventional T cells) from dying from activation-induced apoptosis. The resistance of CCR5-deficient NKT cells from activation-induced apoptosis following Con A administration is not due to a defective Fas-driven death pathway. Moreover, FLF in CCR5-deficient mice also correlated with hepatic CCR5-deficient NKT cells, producing more IL-4, but not IFN-gamma, relative to wild-type NKT cells. Furthermore, FLF in these mice was abolished by IL-4 mAb or NK1.1 mAb treatment. We propose that CCR5 deficiency may predispose individuals to the development of FLF by preventing hepatic NKT cell apoptosis and by regulating NKT cell function, establishing a novel role for CCR5 in the development of this catastrophic liver disease that is independent of leukocyte recruitment.