Anti-inflammatory effects of xanthohumol in RAW 264.7 macrophages are mediated through the activation of AMP kinase

Xanthohumol (XN), a prenylated chalcone extracted from common hop plants, has been studied for its anti-inflammatory properties. In this study, we hypothesize that XN induces M2 polarization of macrophages and the resulting anti-inflammatory effects are mediated through the activation of adenosine monophosphate-activated protein kinase (AMPK) signaling pathway. RAW 264.7 cells were treated with either 0.1% DMSO or XN and the culture supernatant was collected for ELISA and whole cell lysates were collected for western blotting. Our results demonstrate that XN upregulated the secretion of IL10, a signature cytokine for M2 polarization, in RAW264.7 cells. We further demonstrated that XN increased arginase expression, a marker for M2 polarization, and suppressed IFNγ-mediated upregulation of inducible nitric oxide synthase (iNOS) expression, a marker for M1 polarization. Additionally, XN decreased IFNγ – induced elevation of nitrite release, indicating the inhibitory effects of XN against M1 polarization. Furthermore, XN at 25μM increased the secretion of catecholamines from macrophages comparable to IL4, an inducer of M2 phenotype and these effects were accompanied by an increased expression of tyrosine hydroxylase, a rate-limiting enzyme of catecholamine biosynthesis. Finally, XN and AICAR, an AMPK stimulator, upregulated the expression of phospho-AMPK and arginase while dorsomorphin, an established inhibitor of the AMPK pathway failed to do so in RAW264.7 cells. These results provide evidence for the anti-inflammatory effects of XN mediated through the induction of M2 polarization and activation of AMPK signaling pathway.

Chronic inflammation associated with obesity exacerbates bone loss in mice

Dysfunctional adipose tissue characterized by abnormal inflammatory cytokine production during obesity, is linked to several metabolic disorders including bone loss. An increase in bone fracture incidence due to increased rates of obesity is becoming a significant new health concern. However, it is still obscure whether obesity accelerates bone loss. Herein, we have investigated the systemic weight gain, cytokine production, bone turnover markers and femur bone micro-architecture in high-fat diet (HFD) fed obese mice. HFD mice exhibited excessive visceral fat accumulation (2.4 fold) in the peritoneal cavity and increased body weight (2.1 fold) compared to regular chow diet (RCD) fed mice. The serum levels of pro-inflammatory cytokine IL-6 was increased approximately 8-fold in HFD mice compared to RCD mice. The serum bone turnover marker, C-terminal telopeptides of collagen (CTx), was almost 2-fold higher in HFD mice compared to RCD mice. Further, radiological studies from micro computed tomography (micro-CT) of femur suggests that HFD mice exhibited considerably reduced bone volume fraction (BV/TV) and cortical thickness compared to RCD mice. These results suggest the chronic inflammation associated with many metabolic disorders such as obesity may accelerate bone loss.

Novel anti-obesity effects of beer hops compound xanthohumol: role of AMPK signaling pathway

BACKGROUND

Obesity alters adipose tissue metabolic and endocrine functioning, leading to an increased adiposity and release of pro-inflammatory cytokines. Various phytochemicals have been reported to contribute to the beiging of white adipose tissue in order to ameliorate obesity by increasing thermogenesis. Here, we show that the prenylated chalcone, xanthohumol (XN), induces beiging of white adipocytes, stimulates lipolysis, and inhibits adipogenesis of murine 3T3-L1 adipocytes and primary human subcutaneous preadipocytes and these effects are partly mediated by the activation of the AMP-activated protein kinase (AMPK) signaling pathway.

METHODS

3T3-L1 adipocytes and primary human subcutaneous preadipocytes were differentiated using a standard protocol and were treated with various concentrations of XN, dorsomorphin, an AMPK inhibitor, or AICAR, an AMPK activator, to investigate the effects on adipogenesis, beiging and lipolysis.

RESULTS

XN induced beiging of white adipocytes as witnessed by the increased expression of beige markers CIDE-A and TBX-1. XN increased mitochondrial biogenesis, as evidenced by increased mitochondrial content, enhanced expression of PGC-1α, and the thermogenic protein UCP1. Following 24 h of treatment, XN also increased oxygen consumption rate. XN stimulated lipolysis of mature 3T3-L1 and primary human subcutaneous adipocytes and inhibited adipogenesis of maturing adipocytes. XN activated AMPK and in turn, XN-induced upregulation of UCP1, p-ACC, HSL, and ATGL was downregulated in the presence of dorsomorphin. Likewise, an XN-induced decrease in adipogenesis was reversed in the presence of dorsomorphin.

CONCLUSIONS

Taken together, XN demonstrates anti-obesity effects by not only inducing beiging but also decreasing adipogenesis and inducing lipolysis. The anti-obesity effects of XN are partly mediated by AMPK signaling pathway suggesting that XN may have potential therapeutic implications for obesity.

Lipocalin 2 deficiency exacerbates collagen antibody induced arthritis in mice

Rheumatoid arthritis (RA) is associated with elevated levels of a numerous acute phase proteins (APPs), including lipocalin 2 (Lcn2), that drive/dampen the inflammatory response. Lcn2, a 25KDa innate immune protein is known to be significantly up regulated during various inflammatory disorders including antibody-mediated arthritis such as rheumatoid arthritis (RA). However, its biological role remains unclear. Herein we have demonstrated that Lcn2 levels were significantly upregulated during collagen antibody induced arthritis (CAIA). Lcn-2-knockout mice (Lcn2KO) developed more severe serum-induced arthritis compared to wild-type (WT) mice. Histological analysis revealed extensive tissue and bone destruction in Lcn2KO mice compared to WT mice. Furthermore, we have observed reduced immune cell infiltration in Lcn2KO mice compared to WT mice. These studies suggest a crucial role of Lcn2 in resolution of arthritic inflammation, making it a promising target in designing better therapeutic strategies for the treatment of rheumatoid arthritis.

Lipocalin2 mediates anti-inflammatory functions through the inhibition of STAT3 and activation of STAT5 signaling in bone marrow derived macrophages

Lipocalin2 (Lcn2), an innate immune protein, is known to be significantly up-regulated during inflammatory disorders including arthritis, however, its molecular mechanisms remain to be elucidated. We have shown that Lcn2-knockout (Lcn2KO) mice developed more severe serum-induced arthritis (STA) compared to wild-type (WT) mice with significantly reduced neutrophil infiltration but considerably more macrophage migration. Therefore, we have investigated the possible role of Lcn2 in regulating macrophages. Bone marrow cells were isolated from Lcn2KO and WT mice and polarized to classical or inflammatory (M1) and alternate or anti-inflammatory (M2) macrophages. The polarization of M1 (iNOS) and M2 (arginase-1) phenotypes was confirmed by Western blot analysis. We did not observe a difference in polarization of Lcn2KO and WT macrophages suggesting that Lcn2 may not alter the polarization of macrophages. However, anti-inflammatory cytokines such as TGF-β1 and IL-10 were significantly reduced in either LPS or IC-stimulated M2 phenotypes from Lcn2KO mice compared to WT mice. In agreement, we observed systemic elevated levels of pro-inflammatory cytokines in Lcn2KO compared to WT mice during STA. Further, we’ve demonstrated that Lcn2 deficient M1 macrophages displayed increased STAT3 activation compared to WT cells. In addition, WT M2 phenotype exhibited elevated STAT5 activation. Taken together, these results suggest that Lcn2 may promote the down-regulation of pro-inflammatory cytokines and up-regulate anti-inflammatory cytokines possibly through STAT3 and STAT5 signaling pathways as a potential negative feedback loop in order to limit the extent of inflammation during autoimmune arthritis conditions.

Exogenous Lipocalin2 facilitates the upregulation of thermogenic and beige/browning markers in murine white adipocytes

Lipocalin2 (Lcn2) belongs to a small molecular weight lipocalin subfamily of secretory proteins that binds to small hydrophobic molecules. Recent studies have shown that Lcn2 is highly upregulated by adipocytes and is categorized as a new adipokine with a role in innate immunity and metabolic disorders, including obesity. However, the exact role Lcn2 plays in the mediation and progression of obesity has yet to be elucidated. Herein, we have investigated the role of exogenous Lcn2 in inducing the browning of white adipocytes in vitro using the 3T3-L1 murine adipocyte cell line. Treatment with exogenous recombinant Lcn2 (rec-Lcn2) resulted in the upregulation of thermogenic and beige/brown markers (UCP1, PGC-1α, PPARγ, PRDM16, ZIC-1 and TBX1) in mature adipocytes. Additionally, rec-Lcn2 increased mitochondrial activity in 3T3-L1 cells. Further, rec-Lcn2 decreased the pre-adipocyte differentiation resulting in the attenuation of adipogenesis as evidenced by reduced lipid content accumulation. These results suggest that Lcn2 is a naturally occurring adipokine, and may serve as an anti-obesity agent by both decreasing adipogenesis in white adipocytes and inducing the transdifferentiation of white to brown-like beige adipocytes. Therefore, Lcn2 could be a potential target to attenuate/prevent obesity.

Prostaglandin E2 and IL-23 interconnects STAT3 and RoRγ pathways to initiate Th17 CD4+ T-cell development during rheumatoid arthritis

BACKGROUND

The chronic inflammation associated with rheumatoid arthritis (RA) leads to focal and systemic bone erosion of the joints resulting in a crippling disability. Recent reports indicate an increase in the incidence of RA in the coming years, placing a significant burden on healthcare resources. The incidence of RA is observed to be increasing with age and a significant proportion of those new cases will be aggressively erosive.

FINDINGS

The altered physiology, due to immune disturbances, contributes towards RA pathogenesis. The imbalance of inflammatory cytokines and non-cytokine immune modulators such as prostaglandin E2 (PGE2) and IL-23-induced pathogenic IL-17, plays a crucial role in persistent inflammation and bone degradation during RA. However, the molecular mechanism of IL-23, a key cytokine, and PGE2 in the development and perpetuation of IL-17 producing effector Th17 cells is poorly understood.

CONCLUSION

This review focuses on research findings that provide insight into the contribution of PGE2 and IL-23 during the development of pathogenic Th17 cells. We also highlight the key transcriptional factors required for Th17 development and therapeutic strategies to disrupt the interaction between IL-23 and IL-17 to prevent the end-organ damage in RA.

Prostaglandin E2 receptor (EP2): a novel target to attenuate excessive bone loss during autoimmune arthritis

Prostaglandin-E2 receptors (sub type EP2) are known to be activated during various autoimmune inflammatory disorders including rheumatoid arthritis (RA) and may play an essential role in exacerbating the bone damage during RA. Recently, we have reported that EP2 antagonists inhibited pro-inflammatory cytokine responses at the transcriptional level using murine monocytic cell line and observed that EP2 antagonists attenuate the upregulation of several inflammatory mediators in vitro. It has been shown that EP2 gene deletion in mouse cultures impairs osteoclast formation. Herein we investigated the anti-osteoclastogenic activity of recently discovered EP2 antagonists using an in vitro osteoclastogenesis model using mouse monocytic cell line (RAW264.7 cells). We observed significantly increased size and number of osteoclasts by both PGE2 and butaprost (selective EP2 agonist) compared to receptor activator of nuclear factor kappa-B ligand (RANKL) alone treated cells. We did not observe significant difference in number of osteoclasts between PGE2 and butaprost. In addition, 10μM concentration of various EP2 specific antagonists (TG8-4, TG4-155 and TG6-129) inhibited RANKL-induced osteoclast formation. Western blot analysis revealed that EP2 antagonists decreased the expression of c-Fos and nuclear factor of activated T cells c1 (NFATc1), which are the master regulators of osteoclastogenesis. These data indicates the direct effect of EP2 antagonists on bone cells in preventing the severe bone damage implying EP2 receptors play a major role during osteoclast formation, thus EP receptors should be explored as a therapeutic target to blunt the excessive bone loss during arthritis.

Lipocalin2, an innate immune protein, modulates iNOS and arginase-1 in macrophages to promote the anti-inflammatory function

Lipocalin 2 (Lcn2), an innate immune protein, is known to be dramatically up regulated in various inflammatory disorders including autoimmune arthritis, yet its biological role remains unclear. Recently our studies have shown an increase in the accumulation of macrophages in Lcn2 deficient mice compared to wild type (WT) mice in a serum transfer arthritic mouse model. Thus, indicating that the upregulation of Lcn2 might be necessary for the initiation and further resolution of inflammatory processes. In this study, we have investigated the anti-inflammatory function of Lcn2 using murine mouse macrophages. RAW 264.7 cells treated with INFγ and LPS both exhibited pro-inflammatory phenotype, M1, while cells treated with IL-4 displayed an anti-inflammatory phenotype, M2. To determine the anti-inflammatory effects of Lcn2 an IL-10 ELISA revealed that M2 macrophages in the presence of recombinant Lcn2 (rLcn2) significantly increased the expression of IL-10. In addition, arginase-1 expression was found to be significantly upregulated in M2 polarized macrophages in the presence of rLcn2 while inducible nitric oxide synthase (iNOS) expression was down-regulated in the M1 phenotype. However, RAW 264.7 cells treated with Lcn2 alone did not exert either pro- or anti-inflammatory effect. In conclusion, Lcn2 displays the ability to significantly increase the release of anti-inflammatory cytokine, IL-10, thus promoting the anti-inflammatory properties of M2 macrophages. Collectively, our data suggests a crucial role of Lcn2 in the resolution of arthritic inflammation via macrophage polarization, making it a promising target in designing better therapeutic strategies to control the ongoing inflammation during autoimmune arthritis.

Effects of anchor structure and glycosylation of Fcγ receptor III on ligand binding affinity

The anchor structure of CD16 affects its binding affinity in a ligand-specific manner. The ligand binding affinity decreases for human IgG1 but increases for murine IgG2a when the anchor is changed from full to partial to none. Removing N-glycosylation from CD16 also increases the ligand binding affinity.

Isoforms of the Fcγ receptor III (FcγRIII or CD16) are cell surface receptors for the Fc portion of IgG and important regulators of humoral immune responses. Different ligand binding kinetics of FcγRIII isoforms are obtained in three dimensions by surface plasmon resonance and in two dimensions by a micropipette adhesion frequency assay. We show that the anchor structure of CD16 isoforms isolated from the cell membrane affects their binding affinities in a ligand-specific manner. Changing the receptor anchor structure from full to partial to none decreases the ligand binding affinity for human IgG1 (hIgG1) but increases it for murine IgG2a (mIgG2a). Removing N-glycosylation from the CD16 protein core by tunicamycin also increases the ligand binding affinity. Molecular dynamics simulations indicate that deglycosylation at Asn-163 of CD16 removes the steric hindrance for the CD16-hIgG1 Fc binding and thus increases the binding affinity. These results highlight an unexpected sensitivity of ligand binding to the receptor anchor structure and glycosylation and suggest their respective roles in controlling allosterically the conformation of the ligand binding pocket of CD16.

Microbiota-inducible Innate Immune, Siderophore Binding Protein Lipocalin 2 is Critical for Intestinal Homeostasis

Lipocalin 2 (Lcn2) is a multifunctional innate immune protein whose expression closely correlates with extent of intestinal inflammation. However, whether Lcn2 plays a role in the pathogenesis of gut inflammation is unknown. Herein, we investigated the extent to which Lcn2 regulates inflammation and gut bacterial dysbiosis in mouse models of IBD. Lcn2 expression was monitored in murine colitis models and upon microbiota ablation/restoration. WT and Lcn2 knockout (Lcn2KO) mice were analyzed for gut bacterial load, composition by 16S rRNA gene pyrosequencing and, their colitogenic potential by co-housing with Il-10KO mice. Acute (dextran sodium sulfate) and chronic (IL-10R neutralization) colitis was induced in WT and Lcn2KO mice with or without antibiotics. Lcn2 expression was dramatically induced upon inflammation and was dependent upon presence of a gut microbiota and MyD88 signaling. Use of bone-marrow chimeric mice revealed non-immune cells are the major source of circulating Lcn2. Lcn2KO mice exhibited elevated levels of entA-expressing gut bacteria burden and, moreover, a broadly distinct bacterial community relative to WT littermates. Lcn2KO mice developed highly colitogenic T-cells and exhibited exacerbated colitis upon exposure to DSS or neutralization of IL-10. Such exacerbated colitis could be prevented by antibiotic treatment. Moreover, exposure to the microbiota of Lcn2KO mice, via cohousing, resulted in severe colitis in Il-10KO mice. Lcn2 is a bacterially-induced, MyD88-dependent, protein that play an important role in gut homeostasis and a pivotal role upon challenge. Hence, therapeutic manipulation of Lcn2 levels may provide a strategy to help manage diseases driven by alteration of the gut microbiota.

Immune Complex-Induced, Nitric Oxide-Mediated Vascular Endothelial Cell Death by Phagocytes Is Prevented with Decoy FcγReceptors

Autoimmune vasculitis is an endothelial inflammatory disease that results from the deposition of immune-complexes (ICs) in blood vessels. The interaction between Fcgamma receptors (FcγRs) expressed on inflammatory cells with ICs is known to cause blood vessel damage. Hence, blocking the interaction of ICs and inflammatory cells is essential to prevent the IC-mediated blood vessel damage. Thus we tested if uncoupling the interaction of FcγRs and ICs prevents endothelium damage. Herein, we demonstrate that dimeric FcγR-Igs prevented nitric oxide (NO) mediated apoptosis of human umbilical vein endothelial cells (HUVECs) in an in vitro vasculitis model. Dimeric FcγR-Igs significantly inhibited the IC-induced upregulation of inducible nitric oxide synthase (iNOS) and nitric oxide (NO) release by murine monocytic cell line. However, FcγR-Igs did not affect the exogenously added NO-induced upregulation of pro-apoptotic genes such as Bax (15 fold), Bak (35 fold), cytochrome-C (11 fold) and caspase-3 (30 fold) in HUVECs. In conclusion, these data suggest that IC-induced NO could be one of the major inflammatory mediator promoting blood vessel inflammation and endothelial cell death during IC-mediated vasculitis which can be effectively blocked by dimeric decoy FcγRs.

Microbiota-inducible Innate Immune, Siderophore Binding Protein Lipocalin 2 is Critical for Intestinal Homeostasis

BACKGROUND & AIMS

Lipocalin 2 (Lcn2) is a multifunctional innate immune protein whose expression closely correlates with extent of intestinal inflammation. However, whether Lcn2 plays a role in the pathogenesis of gut inflammation is unknown. Herein, we investigated the extent to which Lcn2 regulates inflammation and gut bacterial dysbiosis in mouse models of IBD.

METHODS

Lcn2 expression was monitored in murine colitis models and upon microbiota ablation/restoration. WT and Lcn2 knockout (Lcn2KO) mice were analyzed for gut bacterial load, composition by 16S rRNA gene pyrosequencing and, their colitogenic potential by co-housing with Il-10KO mice. Acute (dextran sodium sulfate) and chronic (IL-10R neutralization and T-cell adoptive transfer) colitis was induced in WT and Lcn2KO mice with or without antibiotics.

RESULTS

Lcn2 expression was dramatically induced upon inflammation and was dependent upon presence of a gut microbiota and MyD88 signaling. Use of bone-marrow chimeric mice revealed non-immune cells are the major contributors of circulating Lcn2. Lcn2KO mice exhibited elevated levels of entA-expressing gut bacteria burden and, moreover, a broadly distinct bacterial community relative to WT littermates. Lcn2KO mice developed highly colitogenic T-cells and exhibited exacerbated colitis upon exposure to DSS or neutralization of IL-10. Such exacerbated colitis could be prevented by antibiotic treatment. Moreover, exposure to the microbiota of Lcn2KO mice, via cohousing, resulted in severe colitis in Il-10KO mice.

CONCLUSION

Lcn2 is a bacterially-induced, MyD88-dependent, protein that play an important role in gut homeostasis and a pivotal role upon challenge. Hence, therapeutic manipulation of Lcn2 levels may provide a strategy to help manage diseases driven by alteration of the gut microbiota.

Immune complex-induced, nitric oxide-mediated vascular endothelial cell death by phagocytes (BA7P.159)

Immune-complex (IC) mediated vascular endothelial cell death linked to the release of toxic free radicals by activated inflammatory cells. In particular, nitric oxide (NO), a highly reactive free radical, is implicated in many IC-mediated inflammatory disorders. However, the mechanisms of NO-induced endothelial cells death during autoimmune vasculitis have not been clearly understood. Therefore, we investigated the molecular mechanisms of extracellularly secreted NO by IC-activated phagocytes on endothelial cells using in-vitro and in-vivo vasculitis models. When co-incubation of antibody-coated endothelial cells, murine macrophages released significantly high levels of NO (12 folds) into the culture media. In addition exogenously added NO induced upregulation of pro-apoptotic genes such as Bax (15 fold), Bak (35 fold), cytochrome-C (11 fold) and caspase-3 (30 fold) in endothelial cells. Further, in vivo studies revealed that circulating ICs deposit and lead to accumulation of inflammatory cells in the capillaries but not in large arteries. In addition, the IC-mediated damages to vascular endothelium are prevented by uncoupling IC and inflammatory cells interaction. In summary these results suggest that, though the complexity of NO-induced cell death signaling exists due to its differential (dichotomous) cellular activities, it is absolutely dangerous for cell survival at sustained and chronic level of production as possibly occurring in IC-mediated autoimmune vasculitis

Antibody effector functions mediated by Fcγ-receptors are compromised during persistent viral infection

T cell dysfunction is well documented during chronic viral infections but little is known about functional abnormalities in humoral immunity. Here we report that mice persistently infected with lymphocytic choriomeningitis virus (LCMV) exhibit a severe defect in Fcγ-receptor (FcγR)-mediated antibody effector functions. Using transgenic mice expressing human CD20, we found that chronic LCMV infection impaired the depletion of B cells with rituximab, an anti-CD20 antibody widely used for the treatment of B cell lymphomas. In addition, FcγR-dependent activation of dendritic cells by agonistic anti-CD40 antibody was compromised in chronically infected mice. These defects were due to viral antigen-antibody complexes and not the chronic infection per se, because FcγR-mediated effector functions were normal in persistently infected mice that lacked LCMV-specific antibodies. Our findings have implications for the therapeutic use of antibodies and suggest that high levels of pre-existing immune complexes could limit the effectiveness of antibody therapy in humans.

Decoy FcγR-Ig molecules ameliorate immune-complex induced blood vessel damage by blocking the release of inflammatory mediators from macrophages (INM2P.432)

Autoimmune vasculitis is an endothelial inflammatory disease that results from deposition of immune-complexes (ICs) in blood vessels. Interaction of FcγRs expressed on inflammatory cells with ICs is known to cause blood vessel damage. Hence, blocking the interaction of ICs and inflammatory cells is prerequisite to prevent the blood vessel damage. Herein, we have shown that dimeric FcγR-Ig (CD16A-Ig and CD32A-Ig) molecules are able to block these interactions using in vitro and in vivo vasculitis models. FcγR-Igs could block 70% of RAW 267.4 cells binding to antibody-coated Human umbilical vein endothelial cells (HUVEC). FcγR-Igs significantly inhibited the IC-mediated expression of inducible nitric oxide synthase (iNOS) and Nitric oxide (NO) release in RAW 264.7 cells. We observed that exogenous NO induced the upregulation of pro-apoptotic genes such as Bax, Bak, caspase-3 and caspase-8 in HUVEC cells. Further, in vivo studies revealed that circulating ICs deposits in the capillaries of various vital organs but not in large arteries. Interestingly, dimeric FcγR-Igs are distributed in the areas where ICs are deposited. The co-localization of ICs and FcγR-Igs revealed that dimeric FcγR-Ig molecules bind specifically to ICs and thus prevent the vascular damage. Taken together, these results suggest that IC-induced NO might be a major factor promoting the blood vessel damage, which can effectively be blocked using recombinant dimeric FcγRs molecules during IC mediated vasculitis.

Discovery and characterization of carbamothioylacrylamides as EP2 selective antagonists

Prostanoid receptor EP2 is emerging as a novel target for development of anti-inflammatory drugs for the treatment of chronic neurodegenerative and peripheral diseases; however, the availability of EP2 antagonist probes for exploration of peripheral disease models is very limited. We now report identification and characterization of a novel chemical class of compounds that show nanomolar potency and competitive antagonism of the EP2 receptor. A compound in this class, TG6-129, showed prolonged plasma half-life and did not cross the blood brain barrier. This compound also suppressed the induction of inflammatory mRNA markers in a macrophage cell line upon activation of EP2. Thus, this compound could be useful as a probe for a variety of peripheral chronic inflammatory diseases such as rheumatoid arthritis and chronic obstructive pulmonary disease, in which EP2 appears to play a pathogenic role.

Differential role of lipocalin 2 during immune complex-mediated acute and chronic inflammation in mice

OBJECTIVE

Lipocalin 2 (LCN-2) is an innate immune protein that is expressed by a variety of cells and is highly up-regulated during several pathologic conditions, including immune complex (IC)-mediated inflammatory/autoimmune disorders. However, the function of LCN-2 during IC-mediated inflammation is largely unknown. Therefore, this study was undertaken to investigate the role of LCN-2 in IC-mediated diseases.

METHODS

The up-regulation of LCN-2 was determined by enzyme-linked immunosorbent assay in 3 different mouse models of IC-mediated autoimmune disease: systemic lupus erythematosus, collagen-induced arthritis, and serum-transfer arthritis. The in vivo role of LCN-2 during IC-mediated inflammation was investigated using LCN-2-knockout mice and their wild-type littermates.

RESULTS

LCN-2 levels were significantly elevated in all 3 of the autoimmune disease models. Further, in an acute skin inflammation model, LCN-2-knockout mice exhibited a 50% reduction in inflammation, with histopathologic analysis revealing notably reduced immune cell infiltration as compared to wild-type mice. Administration of recombinant LCN-2 to LCN-2-knockout mice restored inflammation to levels observed in wild-type mice. Neutralization of LCN-2 using a monoclonal antibody significantly reduced inflammation in wild-type mice. In contrast, LCN-2-knockout mice developed more severe serum-induced arthritis compared to wild-type mice. Histologic analysis revealed extensive tissue and bone destruction, with significantly reduced neutrophil infiltration but considerably more macrophage migration, in LCN-2-knockout mice compared to wild-type mice.

CONCLUSION

These results demonstrate that LCN-2 may regulate immune cell recruitment to the site of inflammation, a process essential for the controlled initiation, perpetuation, and resolution of inflammatory processes. Thus, LCN-2 may present a promising target in the treatment of IC-mediated inflammatory/autoimmune diseases.

GPI-GM-CSF protein transferred onto H5 influenza VLPs remains stably expressed and functionally active (P6168)

Pathogenic H5N1, a lipid-enveloped influenza virus, is a pandemic threat. The use of virus-like particles (VLPs) as an alternative to current influenza vaccines is highly promising. VLPs are similar in structure to their live viral counterparts but do not contain viral genome that is required for replication; hence VLPs provide for a safe and immunogenic vaccine. Although the particulate nature of VLPs allows them to be highly immunogenic, the need for protection against heterotypic viruses still remains. Therefore, inclusion of immunostimulatory molecules (ISMs) onto the VLP surface can help to induce cross-protection against strains and provide for stronger immunity. We were able to show that GPI-anchored-GM-CSF can incorporate stably onto H5 influenza VLP surfaces after a simple and quick protein transfer method. This method allows for the incorporation of the GPI-anchor onto the surface of lipid-bilayered VLPs within a matter of hours and allows for the incorporation of multiple GPI-ISMs in a concentration-dependent manner. Furthermore, protein transferred VLPs were functional in leading to bone marrow derived cell proliferation compared to unmodified VLPs, and incorporated GM-CSF was as functional as equal concentrations of commercially available recombinant soluble GM-CSF. Therefore, VLPs expressing GPI-GM-CSF could lead to enhanced immunogenicity and antiviral immune responses compared to unmodified VLPs.

Regulatory T cell dysfunction in lipocalin 2 knockout mice exacerbates serum-induced arthritis (P1326)

Lipocalin 2 (Lcn2), a 25KDa innate immune protein, known to be dramatically up regulated in various inflammatory disorders including antibody-mediated arthritis, yet its biological role remains unclear. More recently our studies have suggested that the regulation might be necessary for the initiation and further resolution of inflammatory process. However, the exact mechanism involved in this process is still unknown. In this study, we report that Lcn2 is up regulated up to 5 fold during the course of serum-induced arthritis (SIA) in wild type (WT) mice. Likewise, Lcn2KO mice suffered a severe arthritic disease with elevated systemic proinflammatory cytokines as compared to their WT littermates. Immunological analysis revealed a considerable increase in granulocytic population (Gr1+, CD11b+, CD11c+), and a significant decrease (4.2 fold) in regulatory T cell (CD4+, CD25+ and FoxP3+) population in Lcn2KO arthritic mice as compared to their WT littermates. Accordingly, Lcn2KO mice exhibited a defect in T cell proliferation as compared to their WT counterparts, suggesting a novel role for Lcn2 in splenocyte proliferation and T-reg expansion. Collectively, our data suggests a crucial role of Lcn2 in resolution of arthritic inflammation via T-reg expansion, making it a promising target in designing better therapeutic strategies for the treatment of rheumatoid arthritis.

Expression of membrane anchored cytokines and B7-1 alters tumor microenvironment and induces protective antitumor immunity in a murine breast cancer model

Many studies have shown that the systemic administration of cytokines or vaccination with cytokine-secreting tumors augments an antitumor immune response that can result in eradication of tumors. However, these approaches are hampered by the risk of systemic toxicity induced by soluble cytokines. In this study, we have evaluated the efficacy of 4TO7, a highly tumorigenic murine mammary tumor cell line, expressing glycosyl phosphatidylinositol (GPI)-anchored form of cytokine molecules alone or in combination with the costimulatory molecule B7-1 as a model for potential cell or membrane-based breast cancer vaccines. We observed that the GPI-anchored cytokines expressed on the surface of tumor cells greatly reduced the overall tumorigenicity of the 4TO7 tumor cells following direct live cell challenge as evidenced by transient tumor growth and complete regression within 30 days post challenge. Tumors co-expressing B7-1 and GPI-IL-12 grew the least and for the shortest duration, suggesting that this combination of immunostimulatory molecules is most potent. Protective immune responses were also observed following secondary tumor challenge. Further, the 4TO7-B7-1/GPI-IL-2 and 4TO7-B7-1/GPI-IL-12 transfectants were capable of inducing regression of a wild-type tumor growing at a distant site in a concomitant tumor challenge model, suggesting the tumor immunity elicited by the transfectants can act systemically and inhibit the tumor growth at a distant site. Additionally, when used as irradiated whole cell vaccines, 4TO7-B7-1/GPI-IL-12 led to a significant inhibition in tumor growth of day 7 established tumors. Lastly, we observed a significant decrease in the prevalence of myeloid-derived suppressor cells and regulatory T-cells in the tumor microenvironment on day 7 post challenge with 4TO7-B7-1/GPI-IL-12 cells, which provides mechanistic insight into antitumor efficacy of the tumor-cell membrane expressed IL-12. These studies have implications in designing membrane-based therapeutic vaccines with GPI-anchored cytokines for breast cancer.

Ukrain, a plant derived semi-synthetic compound, exerts antitumor effects against murine and human breast cancer and induce protective antitumor immunity in mice

Despite the recent advances in anti-cancer therapies, breast cancer accounts for the highest percentage of estimated new cases among female cancer patients. The anti-cancer drug Ukrain, a plant-derived semi-synthetic compound, has been shown to be effective in a variety of tumor models including colon, brain, ovarian, melanoma and lymphoma. However, the direct cytotoxic effects of Ukrain have yet to be investigated in breast cancer models.

AIM

Herein, we investigated the in vitro and in vivo cytotoxicity of Ukrain using murine (4T07 and TUBO) and human (SKBR-3) breast cancer cell lines.

METHODS

Cells were treated with varying concentrations of Ukrain for up to 72 h and analyzed for viability by trypan blue exclusion, apoptosis by intracellular caspase 3 and Annexin V staining, and proliferative potential by a clonogenic assay. Female BALB/c mice were challenged subcutaneously (s.c.) with 4T07-RG cells and administered 5 mg/kg or 12.5 mg/kg body weight Ukrain intravenously (i.v.) on the same day and 3 days later. Protective immune responses were determined following re-challenge of tumor-free mice 35 days post primary challenge.

RESULTS

Ukrain exposure induced apoptosis in a dose and time-dependent manner with 50 µg/mL Ukrain leading to >50% cell death after 48 h exposure for all three breast cancer cell lines. Ukrain administration (12.5 mg/kg) led to significant inhibition of 4T07 tumor growth in vivo and sustained protective anti-tumor immunity following secondary challenge.

CONCLUSION

Our findings demonstrate the in vitro and in vivo cytotoxic effects of Ukrain on breast cancer cells and may provide insight into designing Ukrain-based therapies for breast cancer patients.

Lipocalin 2 deficiency dysregulates iron homeostasis and exacerbates endotoxin-induced sepsis

Various states of inflammation, including sepsis, are associated with hypoferremia, which limits iron availability to pathogens and reduces iron-mediated oxidative stress. Lipocalin 2 (Lcn2; siderocalin, 24p3) plays a central role in iron transport. Accordingly, Lcn2-deficient (Lcn2KO) mice exhibit elevated intracellular labile iron. In this study, we report that LPS induced systemic Lcn2 by 150-fold in wild-type mice at 24 h. Relative to wild-type littermates, Lcn2KO mice were markedly more sensitive to endotoxemia, exhibiting elevated indices of organ damage (transaminasemia, lactate dehydrogenase) and increased mortality. Such exacerbated endotoxemia was associated with substantially increased caspase-3 cleavage and concomitantly elevated immune cell apoptosis. Furthermore, cells from Lcn2KO mice were hyperresponsive to LPS ex vivo, exhibiting elevated cytokine secretion. Additionally, Lcn2KO mice exhibited delayed LPS-induced hypoferremia despite normal hepatic hepcidin expression and displayed decreased levels of the tissue redox state indicators cysteine and glutathione in liver and plasma. Desferroxamine, an iron chelator, significantly protects Lcn2KO mice from LPS-induced toxicity, including mortality, suggesting that Lcn2 may act as an antioxidant in vivo by regulating iron homeostasis. Thus, Lcn2-mediated regulation of labile iron protects the host against sepsis. Its small size and simple structure may make Lcn2 a deployable treatment for sepsis.

Stable incorporation of functionally active purified GPI-anchored immunostimulatory molecules on H5 influenza VLP surfaces by protein transfer. (113.33)

H5N1 influenza, a bilayered lipid enveloped virus, is highly pathogenic and can lead to a pandemic threat; therefore, a potent vaccine is required. The use of virus-like particles (VLPs) as a vaccine has recently gained importance as they are safe and highly immunogenic. VLPs are similar in size and structure to their viral counterparts but do not contain the viral genome required for replication. Although VLPs are immunogenic, full protection and cross-reactivity to other influenza strains does not always occur; therefore, we aim to modify H5 influenza VLPs to incorporate immunostimulatory molecules (ISMs) by using a protein transfer method. Previously, we have shown that GPI-anchored ISMs (ICAM-1 and IL-12) are able to incorporate onto H5 influenza VLPs by a simple and easy protein transfer method. In this study, we show that purification of GPI-IL-12 does not alter the functionality of the protein in stimulating proliferation of ConA-activated splenocytes suggesting that purified GPI-ISMs remain functionally active. Furthermore, the detection of incorporated GPI-ISMs onto the surface of H5 influenza VLPs by protein transfer was conducted by using immunogold staining electron microscopy and incorporation occurred uniformly as detected by flow cytometry analysis. Moreover, these GPI-ISMs remain stably expressed on the VLP surface for at least a week at 4oC. This study suggests that H5 influenza VLPs can be modified to stably express ISMs on its surface by protein transfer.

The expression of membrane-anchored GM-CSF reduces the tumorigenicity of murine breast cancer cells and correlates with a reduction in MDSCs in vivo (46.36)

Currently under preclinical and clinical investigation are several cancer vaccines using whole tumor cells modified to secrete GM-CSF. However, a potential drawback of such vaccines is the risk of systemic toxicity. To address this concern, we generated a GPI-anchored form of mouse GM-CSF (GPI-mGM-CSF) to be stably expressed on the surface of tumor cells. To determine the immunogenicity of breast cancer cells expressing the GPI-mGM-CSF, we used the TUBO cell line, a highly tumorigenic, non-metastatic tumor cell line that constitutively expresses the HER-2/neu oncogene which is overexpressed in 30% of human breast cancer patients. BALB/c mice were challenged with 1e5 TUBO-WT or TUBO-mGM-CSF cells. At the conclusion of the experiment, mice were sacrificed, spleens were harvested and splenocytes were isolated for flow cytometry analysis following RBC lysis. Splenocytes were stained for the prevalence of immune suppressive cells including myeloid derived suppressor cells (MDSCs). We observed minimal, transient growth of tumors in mice challenged with TUBO-mGM-CSF compared to TUBO-WT. Additionally, we obsesrved a significant reduction in spleen weight and prevalence of CD11b+Gr-1+ MDSCs in these mice. These studies suggest that the addition of a membrane anchored form of GM-CSF to tumor cells can induce an antitumor immune response and inhibit the development of immune suppressive cells such as MDSCs.

Abstract 3537: Manipulation of local and systemic immune suppression by GPI-anchored immune stimulatory proteins

Each day in the United States alone, approximately 3400 people are diagnosed while another 1500 people die from cancer. Breast cancer is the most common form of cancer among females and accounts for the second leading cause of death among female cancer patients. In order to be effective in a therapeutic setting, current immunotherapies must be able to overcome the multiple layers of tumor-induced immune suppression such as modulation of MHC expression and costimulatory molecules (CD80/CD86), expression of inhibitory molecules PDL-1 and GITRL and the secretion of immunosuppressive factors such as VEGF and TGF-β into the tumor microenvironment. These immunosuppressive factors promote the recruitment, differentiation and expansion of regulatory immune cells such as myeloid derived suppressor cells (MDSCs) and regulatory T cells (Tregs) into the tumor microenvironment. Using the 4T07 murine breast cancer model we investigated the effects of expressing GPI-anchored immune stimulatory molecules (GPI-ISMs), namely cytokines (IL-2, IL-12) and the costimulatory protein B7-1, on the surface of the tumor cells. BALB/c mice were challenged subcutaneously (s.c.) with either wild-type 4T07 cells (4T07-WT) or 4T07 cells expressing GPI-ISMs. We observed significant splenomegaly in the mice challenged with 4T07-WT cells relative to the mice challenged with 4T07 cells expressing GPI-ISMs. This observed splenomegaly correlated with tumor size and a 4-5 fold increase in the percentage of splenic CD11b+Gr1+ MDSCs indicating the role of active immune suppression in the tumorigenicity of 4T07 breast cancer cells. We then conducted studies to analyze the effect of GPI-ISMs on infiltrating cells into the tumor microenvironment as well as in the spleen and draining lymph nodes (dLNs). Three groups of mice were challenged (s.c.) with the following cells mixed in a 1:1 ratio with BD Matrigel™ (a solubilized basement membrane preparation derived from a mouse sarcoma): 4T07-WT, 4T07-B7/IL-12 or PBS (control). Seven days post challenge, the Matrigel/tumor, spleen and dLNs were harvested from the mice, digested and analyzed for cellular infiltrates by flow cytometry. We observed that the expression of GPI-ISMs on the surface of tumor cells led to reduced angiogenesis as evidenced by a reduced level of blood vessels and decreased presence of CD4+CD25+FOXP3+ regulatory T cells and CD11b+Gr1+ MDSCs locally at the tumor site and dLNs as well as systemically in the spleen. Additionally, there was a decrease in CD8+PD1+ exhausted T cells at the tumor site. Along with the inhibition of immune suppressive cell populations, the GPI-ISMs increased the presence of CD4+ and CD8+ T cells as well as dendritic cells and B cells. These observations suggest that components of the active immune suppression evident in this model can be inhibited by expressing GPI-ISMs on the surface of the 4T07 tumor cells and could be effective in a therapeutic setting.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3537. doi:1538-7445.AM2012-3537

Hydrodynamic delivery of plasmid DNA encoding human FcγR-Ig dimers blocks immune-complex mediated inflammation in mice

Therapeutic use and function of recombinant molecules can be studied by the expression of foreign genes in mice. In this study, we have expressed human Fcgamma receptor –Ig fusion molecules (FcγR-Igs) in mice by administering FcγR-Ig plasmid DNAs hydrodynamically and compared their effectiveness to purified molecules in blocking immune-complex (IC) mediated inflammation in mice. The concentration of hydrodynamically expressed FcγR-Igs (CD16A^F-Ig, CD32A^R-Ig and CD32A^H-Ig) reached a maximum of 130 μg/ml of blood within 24 h after plasmid DNA administration. The in vivo half-life of FcγR-Igs was found to be 9-16 days and Western blot analysis showed that the FcγR-Igs were expressed as a homodimer. The hydrodynamically expressed FcγR-Igs blocked 50-80% of IC-mediated inflammation up to 3 days in a reverse passive Arthus reaction model. Comparative analysis with purified molecules showed that hydrodynamically expressed FcγR-Igs are more efficient than purified molecules in blocking IC-mediated inflammation and had a higher half-life. In summary, these results suggest that the administration of a plasmid vector with a FcγR-Ig gene can be used to study the consequences of blocking IC-binding to FcγRs during the development of inflammatory diseases. This approach may have potential therapeutic value in treating IC-mediated inflammatory autoimmune diseases such as lupus, arthritis and autoimmune vasculitis.

Adjuvanting influenza virus-like particles with glycophosphatidylinosital-anchored immunostimulatory molecules by protein transfer to enhance antiviral immune responses (106.14)

The effortless nature through which influenza, a bilayered lipid enveloped virus, can spread via an aerosol route and cause mortality is distressing. The use of virus-like particles (VLPs), that consist of a virus’ capsid proteins but not the viral genome required for replication, as vaccine candidates proves beneficial due to their safe nature and structural similarity with the live virus. In this study, we show that the incorporation of GPI-anchored immunostimulatory molecules onto H5 influenza VLPs can be accomplished through a quick, easy and stable protein transfer method. Affinity chromatography was used to purify the GPI-proteins (ICAM-1 and IL-12) from CHO-K1 cell lysates and incorporation onto the VLPs was determined by western blot analysis. To verify that incorporation occurred specifically via the GPI-anchor, PI-PLC treatment before and after incorporation and inhibition by fatty-acid binding proteins was carried out. Finally, electron microscopy was used to determine whether the structural integrity of the VLPs was altered following protein transfer. Our results indicate that incorporation of both GPI-proteins onto influenza H5 VLPs occurred following a 2 hour incubation at 37°C without disturbing the structural integrity of the VLPs. Therefore, this protein transfer method can be used to enhance the immunogenicity of VLPs easily and quickly to then be used as a potential influenza vaccine.

Suppression of inflammation in collagen-induced arthritis by administration of recombinant Fcγ receptors (54.17)

Recently we have shown that immune-complex mediated inflammation can be blocked by recombinant dimeric FcγR-Ig molecules in a mouse Arthus reaction model. In the present study, we have investigated whether administration of FcγR-Ig would inhibit the antibody-mediated hemolytic anemia, thrombocytopenia and arthritis in a mouse model. Systemic Administration of recombinant dimeric low affinity FcγRs such as human CD32A alleles (hCD32AR-Ig and hCD32AH-Ig) did not inhibit or prevent the antibody-induced hemolytic anemia and thrombocytopenia. Interestingly, we observed that after 48 hr of administration both hCD32AR-Ig and hCD32AH-Ig were able to inhibit 27% and 42% of the arthritic inflammation respectively, whereas the combination of hCD32AR-Ig and hCD32AH-Ig was able to inhibit 52% of arthritic inflammation. The severity of arthritis as assessed by inflammation and swelling in each digit and paw was significantly reduced. A single dose of hCD32A-Ig molecules was able to reduce the severity of arthritis up to 4 days, after which the disease returned and reached the maximum severity by day 7. The relapse of arthritis might be due to other mechanisms such as complement pathways or accelerated clearance of administered FcγR-Igs in arthritis mice. In conclusion, soluble dimeric FcγR-Igs could be of potential use in treating antibody-mediated autoimmune diseases such as arthritis but not for autoimmune diseases which affect blood cells such as hemolytic anemia and thrombocytopenia

Lipocalin-2 is involved in immune-complex mediated inflammation (102.23)

Lipocalin-2 (Lcn-2) is an innate immune protein whose expression is upregulated by several orders of magnitude in response to inflammation/injury/infection by variety of cells including neutrophils. However, the role of Lcn-2 induction in IC-induced inflammation is largely unknown. Here in, we have investigated the role of Lcn-2 during IC-mediated inflammation using Lcn-2 knock out (Lcn-2KO) and wild type (WT) mice. IC-mediated inflammation upregulated systemic Lcn-2 in WT mice when compared to naïve mice. The neutrophil chemoattractant KC was significantly elevated in WT, but not in Lcn-2KO mice, in response to IC-induced inflammation. Consistently Lcn-2KO mice showed about 50% reduced IC-mediated inflammation when compared to WT mice. Histopathological analysis of skin biopsy showed reduced inflammatory cell infiltration at inflamed site in Lcn-2KO mice relative to WT mice. Administration of recLcn-2 into Lcn-2KO mice resulted in inflammation similar to that of WT mice in response to IC. Lastly, we observed that neutralization of Lcn-2 via neutralizing mAb significantly reduced inflammation in WT mice. These results suggest that engagement of FcγRs expressed on local inflammatory cells with ICs leads to the induction of Lcn-2. Such IC-induced Lcn-2 expression may be essential for infiltration inflammatory cells at the site of inflammation. Our studies show that therapeutic targeting of Lcn-2 may be useful approach for treating IC-mediated inflammatory/autoimmune diseases

Immune complex-mediated enhancement of secondary antibody responses

Immunologic memory is a hallmark of the vertebrate immune system. The first antigenic exposure leads to a slow and modest immune response, whereas repeated exposure, even many years later, leads to a rapid and exaggerated response that is two to three orders of magnitude greater than the primary. In the case of humoral immunity, the increased efficacy of recall responses is due to the production of amplified levels of Ag-specific Ab, as well as the accelerated kinetics of their production. Current thinking suggests that this is due to selective activation of long-lived, Ag-specific memory B cells. A downside of restricting secondary responses solely to memory cells is that the repertoire of the memory B cell pool remains static while pathogens continue to evolve. In this study, we propose that during secondary responses, naive Ag-specific B cells participate alongside memory cells. We show that immune complexes formed in vivo between the Ag and pre-existing Abs from the primary response activate these naive B cells, inducing them to respond with accelerated kinetics and increased magnitude. Thus, the continued recruitment of new B cell clones after each antigenic exposure enables the immune system to stay abreast of rapidly changing pathogens.

Analysis of cross-species IgG binding to human and mouse Fcgamma receptors (FcγRs) (138.29)

Monoclonal antibodies from various species are in therapeutic and diagnostic use and are used extensively in cell depletion studies in rodents. Therefore, in the present investigation the cross-species IgG binding to FcγRs were performed using recombinant dimeric soluble form of human and mouse FcγRs. We observed that human CD16A was able to bind to rabbit IgG better than human CD32AH and CD32AR. The binding specificity is hCD16>hCD32AH>>hCD32R. Both hCD32A alleles were able to bind mouse and rat IgG subtypes, whereas hCD16 binds weakly. hCD32AR binds mouse IgG1, IgG2a and IgG2b but not IgG3 (IgG1>>IgG2a≥IgG2b) whereas CD32AH binds IgG2a and IgG2b (IgG2a≥IgG2b) only not IgG1 and IgG3. With rat IgG subtypes, hCD32AR binds IgG1>IgG2a>>IgG2b and hCD32AH binds IgG1>IgG2b>IgG2a whereas neither hCD32A alleles bound to IgG2c. We observed that hCD32AR allele binds stronger than hCD32AH to rat IgG. With human IgG subtypes, both hCD16A and hCD32AR binds IgG3>IgG1>>>IgG2≥IgG4, whereas hCD32AH binds IgG3>IgG1>IgG2>>>IgG4. We have also characterized binding specificity of mouse FcγRs (mCD16A, mCD32B and mFcRIV) to rabbit and mouse IgGs. All three mFcγRs binds to rabbit IgG. For mouse IgG subtypes, mCD16A binds IgG2b>IgG2a≥IgG1, mCD32B binds IgG1≥IgG2b>IgG2a, whereas FcRIV binds IgG2a≥IgG2b only, none of the mFcγR bound to mIgG3. In conclusion, cross-species FcγR binding to different IgGs must be taken into consideration when IgG based therapeutics and diagnostics are evaluated in rodents.

Dynamics of the interaction of human IgG subtype immune complexes with cells expressing R and H allelic forms of a low-affinity Fc gamma receptor CD32A

CD32A, the major phagocytic FcgammaR in humans, exhibits a polymorphism in the ligand binding domain. Individuals homozygous for the R allelic form of CD32A (CD32A(R) allele) are more susceptible to bacterial infections and autoimmune diseases as compared with H allelic CD32A (CD32A(H)) homozygous and CD32A(R/H) heterozygous individuals. To understand the mechanisms behind this differential susceptibility, we have investigated the dynamics of the interaction of these allelic forms of CD32A when they are simultaneously exposed to immune complexes (IC). Binding studies using Ig fusion proteins of CD32A alleles showed that the R allele has significantly lower binding not only to human IgG2, but also to IgG1 and IgG3 subtypes. Competition assays using purified molecules demonstrated that CD32A(H)-Ig outcompetes CD32A(R)-Ig for IC binding when both alleles simultaneously compete for the same ligand. CD32A(H)-Ig blocked the IC binding mediated by both the allelic forms of cell surface CD32A, whereas CD32A(R)-Ig blocked only CD32A(R) and was unable to cross-block IC binding mediated by CD32A(H). Two-dimensional affinity measurements also demonstrated that CD32A(R) has significantly lower affinity toward all three subtypes as compared with CD32A(H). Our data suggest that the lower binding of CD32A(R) not only to IgG2 but also to IgG1 and IgG3 might be responsible for the lack of clearance of IC leading to increased susceptibility to bacterial infections and autoimmune diseases. Our data further suggests that in humans, inflammatory cells from CD32A(R/H) heterozygous individuals may predominantly use the H allele to mediate Ab-coated target cell binding during phagocytosis and Ab-dependent cellular cytotoxicity, resulting in a phenotype similar to CD32A(H) homozygous individuals.

Cancer vaccine development: designing tumor cells for greater immunogenicity

Cancer vaccine development is one of the most hopeful and exhilarating areas in cancer research. For this reason, there has been a growing interest in the development and application of novel immunotherapies for the treatment of cancer with the focus being on stimulating the immune system to target tumor cells specifically while leaving normal cells unharmed. From such research has emerged a host of promising immunotherapies such as dendritic cell-based vaccines, cytokine therapies and gene transfer technology. These therapies seek to counteract the poor immunogenicity of tumors by augmenting the host's immune system with a variety of immunostimulatory proteins such as cytokines and costimulatory molecules. While such therapies have proven effective in the induction of anti-tumor immunity in animal models, they are less than optimal and pose a high risk of clinical infeasibility. Herein, we further discuss these immunotherapies as well as a feasible and efficient alternative that, in pre-clinical animal models, allows for the expression of specific immunostimulatory molecules on the surface of tumor cells by a novel protein transfer technology.

Custom designing therapeutic cancer vaccines: delivery of immunostimulatory molecule adjuvants by protein transfer

Attempts to create vaccines for humans against invading pathogens such as viruses and bacteria have met with tremendous success. The process of developing vaccines against these pathogens is greatly aided by the fact that they contain antigens that are entirely foreign to humans. Although the knowledge and strategies developed for designing vaccines against these microbes may be of use in developing cancer vaccines, the poor antigenicity and immunosuppressive ability of cancers pose major hurdles to vaccine development. Established tumors have not only withstood immune screening and selection pressure, making them poor stimulators of an immune response, but have also adapted mechanisms to continue evading immune surveillance by creating an immunosuppressive environment. Also, genetic differences in immune responses to an antigen among individuals result in an antigenic profile that varies from patient to patient. Cancers bear such great similarities to normal cells in the body that, on a molecular level, the differences between cancerous and non-cancerous cells are minor. Therefore, developing vaccines which use the host's own tumor tissues carries the risk of breaking tolerance to self-antigens that are present in the tumor tissue. Vaccination strategies that will optimally stimulate the immune system against tumor specific antigens under immunosuppressive conditions need to be developed. In practical terms, this calls for a method by which therapeutic vaccines may be custom-designed to treat cancers case by case. Ex vivo manipulation of dendritic cells and gene transfer of immunostimulatory molecules in ex vivo expanded tumors are being tested in both experimental models and also in human clinical trials. Some of them have met with limited success. Emerging technologies such as protein transfer, which make it possible to express immunostimulatory molecules on tumor cell membranes, offer the means to develop efficient tumor vaccines that are simple and fast, while being easy to store and administer in human patients. Progress in these techniques will move the cancer vaccine field a step closer towards realizing custom designed cancer vaccines in human clinical settings.

Inhibition of expression of anti-apoptotic protein Bcl-2 and induction of cell death in radioresistant human prostate adenocarcinoma cell line (PC-3) by methyl jasmonate

Hormone refractory human prostate cancer cell lines are known to be radioresistant, a feature attributed to their ability to induce anti-apoptotic proteins of the Bcl-2 family when exposed to radiation. We investigated whether pro-apoptotic compounds such as methyl jasmonate, a plant stress hormone, can counteract the radiation-induced anti-apoptotic mechanism in a human prostate cancer cell line PC-3. Significant (p<0.05) increase in cytotoxicity was observed in the combined treatment groups compared to single treatments with methyl jasmonate or gamma-radiation. Treatment of irradiated PC-3 cells with methyl jasmonate resulted in suppression of anti-apoptotic Bcl-2 protein and elevation of caspase-3 activity. Our results showed increased apoptosis in the combined treatment group as compared to the irradiated group or the untreated control. In summary, methyl jasmonate suppressed the radiation-induced Bcl-2 expression and enhanced the radiation sensitivity of human prostate cancer cells.

Region-specific neutralization of Indian cobra (Naja naja) venom by polyclonal antibody raised against the eastern regional venom: A comparative study of the venoms from three different geographical distributions

Indian cobra (Naja naja) venoms from different geographical locations vary in their composition, biochemical, and pharmacological properties. Venom samples from eastern, western and southern India are compared in this study. The venom from eastern region was found to be the most lethal of the three regional venoms. Monovalent antivenom (NNEV-IgG) prepared against the eastern venom was found to cross-react with the other two regional venoms. NNEV-IgG at an Ag:Ab ratio of 1:25 completely neutralized the lethality of eastern venom. At this ratio, it did not neutralize the other two venoms, but the survival time of experimental mice was extended significantly. Commercially available polyvalent antivenom neutralized the lethality of western venom at an Ag:Ab ratio of 1:60 and increased the survival time of experimental mice injected with eastern and southern venoms marginally. Further, NNEV-IgG neutralized the tested pharmacological and enzymatic activities of all the three venom samples dose dependently, with neutralization potency varying with the geographic origin of the tested venoms. Thus, the present study demonstrates the diversity in the immunological properties of venom from different geographical regions and underscores the importance of developing region-specific antivenoms for therapeutic purpose.

A neurotoxic phospholipase A2 variant: Isolation and characterization from eastern regional Indian cobra (Naja naja) venom

CM-Sephadex C-25 column chromatography profile of Indian cobra (Naja naja) venom from eastern region showed a distinct and a dominant phospholipase peak, peak-10, while it was not seen in either southern or western venom samples. Peak-10 was subjected to CM-Sephadex C-25 and Sephadex G-50 column chromatography to isolate NN-X-PLA(2). NN-X-PLA(2) is a single chain protein with the relative molecular weight of 10kDa by SDS-PAGE. It was toxic to mice with an LD(50) value 0.098 mg/kg body weight (i.p.) and the mice exhibited acute neurotoxic symptoms. Upon indirect stimulation, it inhibited the twitching of frog's gastrocnemius muscle in a dose dependent manner. NN-X-PLA(2) was weakly anticoagulant and devoid of cytotoxicity, myotoxicity, hemorrhage, edema inducing, and directlytic activities and effects on platelet aggregation process. Upon chemical modification independently with p-bromophenacyl bromide and acetic anhydride, NN-X-PLA(2) lost both enzymatic and toxic properties.

Mechanism of Chaperone Function in Small Heat Shock Proteins

Mammalian small heat shock proteins (sHSP) form polydisperse and dynamic oligomers that undergo equilibrium subunit exchange. Current models of their chaperone activity hypothesize that recognition and binding of protein non-native states involve changes in the oligomeric state. The equivalent thermodynamic representation is a set of three coupled equilibria that includes the sHSP oligomeric equilibrium, the substrate folding equilibrium, and the equilibrium binding between the sHSP and the substrate non-native states. To test this hypothesis and define the binding-competent oligomeric state of human Hsp27, we have perturbed the two former equilibria and quantitatively determined the consequences on binding. The substrate is a set of T4 lysozyme (T4L) mutants that bind under conditions that favor the folded state over the unfolded state by 10(2)-10(4)-fold. The concentration-dependent oligomer equilibrium of Hsp27 was perturbed by mutations that alter the relative stability of two major oligomeric states including phosphorylation-mimicking mutations that result in the dissociation to a small multimer over a wide range of concentrations. Correlation of binding isotherms with size exclusion chromatography analysis of the Hsp27 oligomer equilibrium demonstrates that the multimer is the binding-competent state. Binding occurs through two modes, each characterized by different affinity and number of binding sites, and results in T4L.Hsp27 complexes of different hydrodynamic properties. Mutants of the Hsp27 phosphorylation mimic that reverse the reduction in oligomer size also reduce the extent of T4L binding. Taken together, these results suggest a central role for the oligomeric equilibrium in regulating the chaperone activity of sHSP. The mutants identify sequence features important for modulating this equilibrium.

Isolation and characterization of hyaluronidase a "spreading factor" from Indian cobra (Naja naja) venom

Hyaluronidase, ubiquitous enzyme in snake venoms, known originally as "spreading factor", has not been well studied. The present study describes the purification and characterization of hyaluronidase from Indian cobra (Naja naja) venom and provides systematic evaluation of the spreading property of the enzyme. Hyaluronidase (NNH1) has been purified through gel permeation and ion exchange chromatography. The molecular mass was found to be 70.406 kDa by MALDI-TOF mass spectrometry and with the (p)i pI of 9.2. The amino acid sequence of the N-terminus was found to be NEQSTHGAYV. The enzyme shows absolute specificity for hyaluronan and belongs to the group of neutral active enzymes. Tetrasaccharides are the final product of hyaluronan digestion. The enzyme cleaves beta 1,4-glycosidic linkage and belongs to a group of endo-beta-N-acetyl hexosaminidases. Hyaluronidase indirectly potentiates the myotoxicity of VRV-PL-VIII, a phospholipolytic myotoxin, and also the hemorrhagic potency of a hemorrhagic complex-I. Localization of hyaluronan in human skin section and selective degradation by venom hyaluronidase (NNH1) corroborate the plausible in vivo degradation of hyaluronan in the extracellular matrix (ECM) resulting in easy dissemination of VRV-PL-VIII myotoxin and hemorrhagic complex-I.