Differential regulation of T-cell dependent and T-cell independent antibody responses through arginine methyltransferase PRMT1 in vivo.

Protein arginine methyltransferase 1 (PRMT1), a major PRMT in mammalian cells, has been shown to play a crucial role in multiple biological functions in vitro. To explore the role of PRMT1 in B cells in vivo, we generated B cell-specific PRMT1-deficient (Prmt1(-/-) ) mice using a Cre-loxP system. Prmt1(-/-) mice showed a defect in B-cell development with diminished levels of serum antibodies. Antibody responses in Prmt1(-/-) mice were absent after stimulation with the type 2 T cell-independent antigen NP-Ficoll but intact after stimulation with the T cell-dependent antigen NP-OVA. Our findings comprise the first evidence showing that PRMT1 is necessary for lymphocyte functions in vivo.

Vaccination with OVA-bound nanoparticles encapsulating IL-7 inhibits the growth of OVA-expressing E.G7 tumor cells in vivo.

Immunotherapy has gained special attention due to its specific effects on tumor cells and systemic action to block metastasis. We recently demonstrated that ovalbumin (OVA) conjugated to the surface of nanoparticles (NPs) (OVA­NPs) can manipulate humoral immune responses. In the present study, we aimed to ascertain whether vaccination with OVA-NPs entrapping IL-7 (OVA-NPs-IL-7) are able to induce antitumor immune responses in vivo. Pretreatment with a subcutaneous inoculation of OVA-NPs delayed the growth of thymic lymphoma cells expressing a model tumor antigen OVA (E.G7-OVA), and OVA-NPs-IL-7 substantially blocked the growth of E.G7-OVA tumor cells, although NPs-IL-7 alone had a meager effect, as assessed by the mean tumor size and the percentage of tumor-free mice. However, pretreatment with OVA-NPs-IL-7 failed to reduce the growth of parental thymic tumor cells, suggesting that the antitumor effect was antigen-specific. A tetramer assay revealed that vaccination with OVA-NPs-IL-7 tended to enhance the proportion of cytotoxic T cells (CTLs) specific for OVA. When the tumor-free mice inoculated with OVA-NPs-IL-7 plus EG.7 cells were rechallenged with E.G7-OVA cells, they demonstrated reduced growth compared with that in the control mice. Thus, a single subcutaneous injection of OVA-NPs-IL-7 into mice induced tumor-specific and also memory-like immune responses, resulting in regression of tumor cells. Antigens on NPs entrapping IL-7 would be a promising carrier to develop and enhance immune responses, including humoral and cellular immunity as well as a method of drug delivery to a specific target of interest.

OVA-bound nanoparticles induce OVA-specific IgG1, IgG2a, and IgG2b responses with low IgE synthesis.

There is an urgent requirement for a novel vaccine that can stimulate immune responses without unwanted toxicity, including IgE elevation. We examined whether antigen ovalbumin (OVA) conjugated to the surface of nanoparticles (NPs) (OVA-NPs) with average diameter of 110nm would serve as an immune adjuvant. When BALB/c mice were immunized with OVA-NPs, they developed sufficient levels of OVA-specific IgG1 antibody responses with low levels of IgE synthesis, representing helper T (Th)2-mediated humoral immunity. OVA-specific IgG2a and IgG2b responses (i.e., Th1-mediated immunity) were also induced by secondary immunization with OVA-NPs. As expected, immunization with OVA in alum (OVA-alum) stimulated humoral immune responses, including IgG1 and IgE antibodies, with only low levels of IgG2a/IgG2b antibodies. CD4-positive T cells from mice primed with OVA-NPs produced substantial levels of IL-21 and IL-4, comparable to those from OVA-alum group. The irradiated mice receiving OVA-NPs-primed B cells together with OVA-alum-primed T cells exhibited enhanced anti-OVA IgG2b responses relative to OVA-alum-primed B cells and T cells following stimulation with OVA-NPs. Moreover, when OVA-NPs-primed, but not OVA-alum-primed, B cells were cultured in the presence of anti-CD40 monoclonal antibody, IL-4, and IL-21, or LPS plus TGF-ß in vitro, OVA-specific IgG1 or IgG2b antibody responses were elicited, suggesting that immunization with OVA-NPs modulates B cells to generate IgG1 and IgG2b responses. Thus, OVA-NPs might exert their adjuvant action on B cells, and they represent a promising potential vaccine for generating both IgG1 and IgG2a/IgG2b antibody responses with low IgE synthesis.

PKC-δ mediates interferon-α-induced apoptosis through c-Jun NH2-terminal kinase activation.

BACKGROUND: Interferon-α (IFN-α) exerts an anti-tumor effect at least through induction of apoptosis in a variety of types including B lymphoma cells. We recently found that IFN-α induced a sustained activation of c-Jun NH2-terminal kinase1 (JNK1), which is implicated in activation of the tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) promoter. In the present study, we explored upstream component(s) of the prolonged IFN-α-initiated activation of JNK1. RESULTS: IFN-α caused activation of PKC-δ in Daudi B lymphoma cells and myeloma U266 cells, as detected by Western blotting using a monoclonal antibody specific for the phosphorylated form of PKC-δ. The dominant-negative form of mutant PKC-δ (dnPKC-δ) reduced the IFN-α-induced JNK1 activation, TRAIL promoter activity, loss of mitochondrial membrane potential (ΔΨm), and increase in propidium iodide (PI) positive cells. The IFN-α-induced activation of JNK1 and the TRAIL promoter was also attenuated by the PKC-δ inhibitor rottlerin. Moreover, a constitutively active form of mutant PKC-δ enhanced the IFN-α-induced TRAIL promoter activity and loss of ΔΨm in Daudi B lymphoma cells. In addition, IFN-α-induced Ser727 phosphorylation of Stat1 was also abrogated by dnPKC-δ. CONCLUSIONS: IFN-α induced JNK1 activation via PKC-δ, leading to upregulation of TRAIL. The interaction of the consequent enhanced TRAIL expression with TRAIL-receptor results in a loss of ΔΨm and increase in PI positive cells. The IFN-α-induced apoptotic events may also be affected by the Ser727-Stat1 induced by PKC-δ-mediated signaling component(s).

Identification of markers that distinguish IgE- from IgG-mediated anaphylaxis.

IgG-mediated anaphylaxis occurs in mice and may contribute to human reactions to infused drugs. To distinguish IgE- from putative IgG-mediated human anaphylaxis, we developed blood markers for murine anaphylaxis and evaluated their human relevance. Both IgG- and IgE-mediated anaphylaxis were characterized by decreased basophil and monocyte percentages and an increased neutrophil percentage in mouse blood. IgE- but not IgG-mediated murine anaphylaxis was accompanied by large increases in IL-4 secretion, plasma soluble IL-4 receptor-α (IL-4Rα) concentration, and T-cell membrane IL-4Rα expression. T-cell IL-4Rα expression also increased when mice that express human Fcε receptor Iα were sensitized with IgG-depleted serum from a peanut-allergic individual and challenged with peanut extract. Increased T-cell IL-4Rα expression is likely to also be a marker for human IgE-mediated anaphylaxis, because IgE-activated human basophils secrete IL-4, and IL-4 increases human T-cell IL-4Rα expression in vitro. Murine IgG- but not IgE-mediated anaphylaxis was characterized by decreased neutrophil Fcγ receptor III (FcγRIII) expression that was observed even when the antigen dose was insufficient to induce shock. Human neutrophils cultured with IgG immune complexes also lost FcγRIII. These observations suggest that decreased blood neutrophil FcγRIII expression without increased IL-4Rα expression can be used to determine whether and when IgG-mediated anaphylaxis occurs in man.

Selective stimulation of IL-4 receptor on smooth muscle induces airway hyperresponsiveness in mice.

Production of the cytokines IL-4 and IL-13 is increased in both human asthma and mouse asthma models, and Stat6 activation by the common IL-4/IL-13R drives most mouse model pathophysiology, including airway hyperresponsiveness (AHR). However, the precise cellular mechanisms through which IL-4Rα induces AHR remain unclear. Overzealous bronchial smooth muscle constriction is thought to underlie AHR in human asthma, but the smooth muscle contribution to AHR has never been directly assessed. Furthermore, differences in mouse versus human airway anatomy and observations that selective IL-13 stimulation of Stat6 in airway epithelium induces murine AHR raise questions about the importance of direct IL-4R effects on smooth muscle in murine asthma models and the relevance of these models to human asthma. Using transgenic mice in which smooth muscle is the only cell type that expresses or fails to express IL-4Rα, we demonstrate that direct smooth muscle activation by IL-4, IL-13, or allergen is sufficient but not necessary to induce AHR. Five genes known to promote smooth muscle migration, proliferation, and contractility are activated by IL-13 in smooth muscle in vivo. These observations demonstrate that IL-4Rα promotes AHR through multiple mechanisms and provide a model for testing smooth muscle-directed asthma therapeutics.

Interferon-alpha induces transient upregulation of c-FLIP through NF-kappaB activation.

Interferon-alpha (IFN-alpha) induces apoptosis in some cell types and promotes cell survival in other cell types, but the molecular mechanisms underlying distinct IFN-alpha-induced cell behaviours remain poorly understood. In the present study, we show that IFN-alpha induced the cellular FLICE (FADD-like interleukin-1 beta-converting enzyme) inhibitory protein (c-FLIP), which serves as a promoter of cell survival in human B lymphoma cells. IFN-alpha induction of transient upregulation of c-FLIP was partially abrogated by the NF-kappaB inhibitor BAY11-7082 (BAY). Pretreatment with BAY sensitized both Daudi and U266 cells to the IFN-alpha-induced loss of mitochondrial membrane potential (DeltaPsi(m)). IFN-alpha phosphorylated the PKC isoform PKCalpha at a threonine residue, and the PKCalpha/betaI inhibitor Go6976 abrogated upregulation of IFN-alpha-induced NF-kappaB activity, leading to sensitization of cells to IFN-alpha-induced apoptosis. To analyze the role of PKCalpha in the IFN-alpha-induced signaling, Daudi cells overexpressing a constitutively active mutant of PKCalpha (caPKCalpha) were used. The caPKCalpha-expressing Daudi cells were partially resistant to the IFN-alpha-induced loss of DeltaPsi(m), concomitant with elevated levels of c-FLIP protein. Together, these results demonstrate that IFN-alpha causes a transient upregulation of c-FLIP expression, at least through PKCalpha-mediated activation of NF-kappaB. The balance between IFN-alpha-induced pro-apoptotic and survival signals determines the cell fate. Thus, therapeutic intervention in this balance may be effective for treatment of patients with IFN-alpha-refractory tumours.

Interferon-alpha-induced apoptosis via tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-dependent and -independent manner.

IFN-alpha regulates tumor cell growth at least through induction of apoptosis. We have recently demonstrated that IFN-alpha causes apoptosis through upregulation of TNF-related apoptosis-inducing ligand (TRAIL) in Daudi B lymphoma and U266 myeloma cells. However, other cell lines such as Ramos and RPMI 8226 underwent apoptosis without any apparent involvement of TRAIL following IFN-alpha stimulation. In this study, we examined whether the IFN-alpha-induced upregulation of TRAIL is essential for the induction of apoptosis. IFN-alpha-induced early phase (48 h) of loss of DeltaPsim was substantially prevented in Daudi B lymphoma cells overexpressing the dominant-negative form of Fas-associated death domain (dnFADD) compared with vector control, whereas a late phase (72 h) of DeltaPsim was comparable to the control. The IFN-alpha-induced early phase of apoptosis was also reduced in the dnFADD-expressing cells, while the late phase of apoptosis was unaffected. IFN-alpha-induced upregulation of TRAIL protein in the dnFADD-expressing Daudi or U266 cells was comparable to their control cells, suggesting that FADD is not involved in the IFN-alpha-induced upregulation of TRAIL. Moreover, the early phase of mitochondrial depolarization was severely prevented by the presence of fusion protein of TRAIL receptor 1 and Fc portion of immunoglobulin (TRAIL-R1:Fc) and TRAIL-R2:Fc. Together, IFN-alpha induces apoptosis in a TRAIL-dependent or -independent manner, depending on the course of the apoptotic process.

IFN-alpha sensitizes daudi B lymphoma cells to anti-IgM induced loss of mitochondrial membrane potential through activation of c-Jun NH(2)-terminal kinase.

Interferon-alpha (IFN-alpha) regulates multiple biologic functions, including antiviral activity, immune regulation, cell differentiation, and cell survival or death, in a variety of cell types. We and others have recently demonstrated that IFN-alpha induces cell death through activation of c-Jun NH(2)-terminal kinase (JNK) in human Daudi B lymphoma and U266 myeloma cells. Moreover, the IFN-alpha-induced signaling pathway has been shown to cross talk with the antigen receptor-mediated signaling cascade. In the present study, we examined whether IFN-alpha affects cell death after engagement of membrane immunoglobulin (mIg) using anti-IgM. Daudi cells pretreated with low concentrations of IFN-alpha (25 or 250 U/mL) for 24 h were stimulated with anti-IgM (1-10 microg/mL) for 24 h. The cells were assayed for JNK activation, mitochondrial membrane potential (DeltaPsim) by Western blotting, and DiOC(6) staining, respectively. The IFN-alpha-primed Daudi cells showed an increased sensitivity to subsequent stimulation with anti-IgM, as assessed by JNK activation and DeltaPsim. Moreover, Daudi cells overexpressing the constitutively active or dominant-negative form of JNK were substantially susceptible or resistant to anti-IgM-induced DeltaPsim, respectively, compared with cells overexpressing the control vector alone. Taken together, these results indicate that IFN-alpha renders Daudi B lymphoma cells susceptible to anti-IgM-induced apoptosis, probably through upregulation of JNK activation.

Requirement of c-Jun NH2-terminal kinase activation in interferon-alpha-induced apoptosis through upregulation of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) in Daudi B lymphoma cells.

Interferon alpha (IFN-alpha) inhibits growth, at least in part, through induction of apoptosis. However, the molecular mechanisms underlying IFN-alpha-induced apoptosis are not completely understood. In the present study, we found that IFN-alpha induced a sustained activation of c-Jun N-terminal kinase 1 (JNK1), but not extracellular kinases (ERKs), in Daudi B lymphoma cells, as assessed by Western blotting using phospho-specific antibodies. Several lines of evidence support the notion that the IFN-alpha-induced activation of JNK is responsible for IFN-alpha-induced apoptosis, at least in part, through upregulation of TNF-related apoptosis-inducing ligand (TRAIL). First, pretreatment of Daudi cells with a JNK inhibitor reduced IFN-alpha-induced upregulation of TRAIL and loss of mitochondrial membrane potential (DeltaPsim) and annexin-positive cells, which was assessed by flow cytometry. Second, a dominant-negative form of JNK1 (dnJNK1) also reduced these apoptotic events, while a constitutively active form of JNK1, MKK7-JNK1beta, enhanced them. Finally, treatment with IFN-alpha enhanced the promoter activity of the TRAIL gene, which was partially abrogated by either JNK inhibitor or dnJNK1, while it was moderately enhanced by MKK7-JNK1beta. These findings are useful for understanding molecular mechanisms of IFN-alpha-induced apoptosis and also for development of treatment modalities of some tumors with IFN-alpha.

Id3-mediated enhancement of cisplatin-induced apoptosis in a sarcoma cell line MG-63.

The molecular mechanism(s) underlying the resistance to cis-diamminedichloroplatinum (CDDP)-induced growth inhibition include DNA repair, apoptosis and cell cycle progression. Inhibitor of differentiation (Id) proteins, which belong to the group of helix-loop-helix proteins, regulate cell cycle progression, differentiation and apoptosis. We examined whether CDDP exposure modulates the expression pattern of Ids and whether ectopic expression of Ids influences CDDP-induced cell death. Cell growth was assessed by WST-8 assay kit. Reactive oxygen species (ROS) was evaluated by flow cytometry using dihydroethidium. MG-63 sarcoma cells were stimulated with CDDP for various times and Id expression was assessed by reverse transcription-polymerase chain reaction. CDDP induced a considerable transient up-regulation of Id3 mRNA, but not Id2, 1-2 h after stimulation. Enforced expression of Id3 caused the MG-63 sarcoma cells to be more sensitive to CDDP-induced growth inhibition, through generation of ROS and caspase-3 activation. Together, our results suggest that CDDP-induced cell death appears to involve Id3.

Cerivastatin-induced apoptosis of human aortic smooth muscle cells through partial inhibition of basal activation of extracellular signal-regulated kinases.

BACKGROUND: The beneficial effects of cerivastatin including hypolipidemic properties have been demonstrated to involve nonlipid as well as lipid mechanisms. In the present study, we examined the mechanisms underlying cerivastatin-induced growth inhibition of human aortic smooth muscle (ASM) cells. METHODS: Human ASM cells were cultured in 96-well plates with or without cerivastatin in the presence or absence of mitogen-activated protein (MAP) kinase (MAPK)/extracellular signal-regulated kinase (ERK) kinase MEK1/MEK 2 inhibitor PD98059. Cell growth was assessed by colorimetric quantitation of NADH, and cell viability was determined by trypan blue dye exclusion method. The induction of apoptosis was determined by propidium iodide (PI) staining method using flow cytometer. The activation of ERKs or c-Jun N-terminal kinases (JNKs) was determined by Western blotting using antibodies (Abs) specific for phospho-ERKs or phospho-JNKs. RESULTS: Treatment of the ASM cells with cerivastatin prevented cell growth in a concentration-dependent manner through at least induction of apoptosis. The cerivastatin-induced apoptosis was reversed by coincubation with isoprenoid [mevalonate, geranylgeranyl pyrophosphate (GGPP), and farnesyl pyrophosphate (FPP)] suggesting a role for isoprenoid in the cerivastatin-induced apoptosis. The cerivastatin cooperated with a MEK1/MEK2 inhibitor PD98059 to induce apoptosis, which appeared to correlate with down-regulation of ERK activation (phospho-ERKs expression) induced by the combination. CONCLUSION: Cerivastatin-induced blockade of ERK activation in ASM cells might result in growth inhibition including apoptosis, which might explain some aspects of the beneficial effects of cerivastatin on coronary artery disease.

Retrovirus-mediated transduction of TRAIL and chemotherapeutic agents co-operatively induce apoptotic cell death in both sarcoma and myeloma cells.

BACKGROUND: Resistance to multiple chemotherapeutic agents results from a variety of factors including a lack of apoptosis in tumor cells. To induce apoptosis in two types of tumor cells, RPMI-8226 and MG-63, a combination of chemotherapeutic agents and retroviral transduction of TRAIL was employed. MATERIALS AND METHODS: Both TRAIL-sensitive 8226 and -resistant MG-63 cells were pretreated with the anti-tumor agent doxorubicin or cisplatin for 24 hours, washed and then exposed to retroviral transduction with TRAIL for a further 24 hours, followed by assay for cell survival using a WST-8 kit. RESULTS: Doxorubicin or cisplatin sensitized both RPMI-8226 and MG-63 cells to TRAIL-induced death in a synergistic manner. This combined treatment was also effective in the MG-63 cells overexpressing Bcl-xL, which are resistant to multiple chemotherapeutic agents. CONCLUSION: A retroviral transduction of TRAIL in conjunction with anti-tumor agents could provide a new treatment modality for the treatment of patients with multiple-drug resistance.

Calpain-induced Bax-cleavage product is a more potent inducer of apoptotic cell death than wild-type Bax.

Wild type (wt) p21 Bax was cleaved to generate p18 Bax during apoptotic processes by calpain, which was suggested to recognize a certain motif around amino acids 30-33 Phe-Ile-Gln-Asp (FIQD). In the present study, analysis of protein sequencing revealed that the cleavage site was between Gln28 and Gly29. The fragment lacking the NH(2)-terminal amino acids 1-28 (tBax(29)) was more apoptotic than wt Bax. The tBax(29)-induced apoptotic cell death was substantially resistant to Bcl-x(L)-mediated rescue, compared with wt Bax, in spite of the complex formation between these two molecules. Together, the tBax(29) would be valuable for the treatment of tumors with high levels of Bcl-x(L) as well as the understanding of Bax-mediated apoptotic processes.

Enhanced expression of the apoptosis inducing ligand TRAIL in mononuclear cells after myocardial infarction.

Tumor necrosis factor (TNF) family proteins including TNF-alpha and Fas (CD95)-ligand have been implicated in the development of acute myocardial infarction (AMI). We studied whether AMI patients displayed up-regulation of another TNF family member, TNF-related-apoptosis-inducing ligand (TRAIL), on peripheral blood mononuclear cells (PBMCs). We compared expression of TRAIL on PBMCs from 26 patients in the acute phase of AMI with that on PBMCs from 16 healthy control subjects using flow cytometry and RT-PCR. In addition, expression of TRAIL protein on PBMCs from patients in the acute phase of AMI was also compared with that from the same patients 7 days later. Furthermore, we compared the expression of TRAIL protein on CD4+, CD8+, CD14+, and CD19+ cells from patients in the acute phase of AMI with that from control subjects using flow cytometry. Finally, expression of the TRAIL receptors (TRAILR)-1 and TRAILR-2 in human cardiomyocytes was examined immunohistochemically. Expression of TRAIL protein was significantly higher in the acute phase of AMI than in control subjects. Expression of TRAIL protein was significantly higher in the acute phase of AMI than 7 days later. TRAIL mRNA expression in the acute phase of AMI was higher than in control subjects. Expression of TRAIL protein on CD4+ and CD14+ cells from AMI patients was significantly higher than that from control subjects. Expression of TRAILR-1 and TRAILR-2 in human cardiomyocytes was confirmed immunohistochemically. TRAIL on infiltrating CD4 and CD146 cells may be involved in the induction of cardiomyocyte apoptosis after AMI.