Dipeptidylpeptidase 4 inhibition enhances lymphocyte trafficking, improving both naturally occurring tumor immunity and immunotherapy.

The success of antitumor immune responses depends on the infiltration of solid tumors by effector T cells, a process guided by chemokines. Here we show that in vivo post-translational processing of chemokines by dipeptidylpeptidase 4 (DPP4, also known as CD26) limits lymphocyte migration to sites of inflammation and tumors. Inhibition of DPP4 enzymatic activity enhanced tumor rejection by preserving biologically active CXCL10 and increasing trafficking into the tumor by lymphocytes expressing the counter-receptor CXCR3. Furthermore, DPP4 inhibition improved adjuvant-based immunotherapy, adoptive T cell transfer and checkpoint blockade. These findings provide direct in vivo evidence for control of lymphocyte trafficking via CXCL10 cleavage and support the use of DPP4 inhibitors for stabilizing biologically active forms of chemokines as a strategy to enhance tumor immunotherapy.

Truncated CXCL10 is associated with failure to achieve spontaneous clearance of acute hepatitis C infection.

UNLABELLED: The pathogenesis of hepatitis C virus (HCV) infection is strongly influenced by the nature of the host's antiviral immunity. Counterintuitively, elevated serum concentrations of C-X-C chemokine 10 (CXCL10), a potent chemoattractant for antiviral T-cells and NK-cells, are associated with poor treatment outcomes in patients with chronic HCV. It has been reported that an N-terminal truncated form of CXCL10, generated by the protease dipeptidylpeptidase 4 (DPP4), can act as chemokine antagonist. We sought to investigate CXCL10 antagonism in the clinical outcome and evolution of acute HCV infection. We collected serial blood samples from 16 patients, at the clinical onset of acute HCV infection and at 12 standardized follow-up timepoints over the first year. Intact and truncated CXCL10 and DPP4 activity were quantified in all longitudinal samples. In addition, NK-cell frequency/phenotype, and HCV-specific T-cell responses were assessed. Subjects developing chronicity (n = 11) had higher concentrations of CXCL10 (P < 0.001), which was predominantly in a truncated form (P = 0.036) compared to patients who spontaneously resolved infection (n = 5). Truncated CXCL10 correlated with HCV-RNA (r = 0.40, P < 0.001) and DPP4 activity (r = 0.53, P < 0.001). Subjects who resolved infection had a higher frequency of HCV-specific interferon-gamma (IFNγ)-producing T-cells (P = 0.017) and predominance of cytotoxic NK-cells (P = 0.005) compared to patients who became chronic. Patients who became persistently infected had higher proportions of cytokine-producing NK-cells, which were correlated with concentrations of truncated CXCL10 (r = 0.92, P < 0.001). CONCLUSION: This study provides the first evidence of chemokine antagonism during acute HCV infection. We suggest that the DPP4-CXCL10 axis inhibits antiviral innate and adaptive host immunity and favors establishment of viral persistence.

CXCL10 antagonism and plasma sDPPIV correlate with increasing liver disease in chronic HCV genotype 4 infected patients.

Egypt has the highest prevalence of hepatitis C virus infection worldwide. CXCL10 is a potent chemoattractant that directs effector lymphocytes to sites of inflammation. It has been reported that plasma CXCL10 is processed by dipeptidylpeptidase IV (DPPIV) thus leading to the generation of an antagonist form. Using Luminex-based immunoassays we determined the concentration of different forms of CXCL10 (total, agonist, and antagonist). We also evaluated plasma soluble DPPIV (sDPPIV) concentration and plasma dipeptidylpeptidase (DPP) activity. Using flow cytometry and immunohistochemistry, we analyzed the distribution of lymphocyte subsets. Plasma CXCL10 was elevated in chronic HCV patients, however the agonist form was undetectable. Increased sDPPIV concentration and DPP activity supported the NH2-truncation of CXCL10. Finally, we demonstrated an increased frequency of CXCR3(+) cells in the peripheral blood, and low numbers of CXCR3(+) cells within the lobular regions of the liver. These findings generalize the observation of chemokine antagonism as a mechanism of immune modulation in chronic HCV patients and may help guide the use of new therapeutic immune modulators.

Critical role of NADPH oxidase in neuronal oxidative damage and microglia activation following traumatic brain injury.

BACKGROUND: Oxidative stress is known to play an important role in the pathology of traumatic brain injury. Mitochondria are thought to be the major source of the damaging reactive oxygen species (ROS) following TBI. However, recent work has revealed that the membrane, via the enzyme NADPH oxidase can also generate the superoxide radical (O(2)(-)), and thereby potentially contribute to the oxidative stress following TBI. The current study thus addressed the potential role of NADPH oxidase in TBI. METHODOLOGY/PRINCIPAL FINDINGS: The results revealed that NADPH oxidase activity in the cerebral cortex and hippocampal CA1 region increases rapidly following controlled cortical impact in male mice, with an early peak at 1 h, followed by a secondary peak from 24-96 h after TBI. In situ localization using oxidized hydroethidine and the neuronal marker, NeuN, revealed that the O(2)(-) induction occurred in neurons at 1 h after TBI. Pre- or post-treatment with the NADPH oxidase inhibitor, apocynin markedly inhibited microglial activation and oxidative stress damage. Apocynin also attenuated TBI-induction of the Alzheimer's disease proteins ß-amyloid and amyloid precursor protein. Finally, both pre- and post-treatment of apocynin was also shown to induce significant neuroprotection against TBI. In addition, a NOX2-specific inhibitor, gp91ds-tat was also shown to exert neuroprotection against TBI. CONCLUSIONS/SIGNIFICANCE: As a whole, the study demonstrates that NADPH oxidase activity and superoxide production exhibit a biphasic elevation in the hippocampus and cortex following TBI, which contributes significantly to the pathology of TBI via mediation of oxidative stress damage, microglial activation, and AD protein induction in the brain following TBI.

Cutting edge: independent roles for IRF-3 and IRF-7 in hematopoietic and nonhematopoietic cells during host response to Chikungunya infection.

The host response to Chikungunya virus is dependent on the direct action of type I IFN on infected nonhematopoietic cells. Prior studies have demonstrated that multiple host sensors coordinate an antiviral response; however, the tissue source(s) and signaling pathways for IFN production remain unknown. In this study, we demonstrate that IRF-3 and IRF-7 are functionally redundant, but lack of both factors results in lethal infection in adult mice. Reciprocal bone marrow chimeras indicated that IRF-3 or IRF-7 expression in either hematopoietic or nonhemotopoietic cell compartments was capable of inducing an antiviral response. Interestingly, redundancy of IRF-3 and IRF-7 was age dependent, as neonatal animals lacking either factor succumbed to infection. We further demonstrate that IPS-1 is essential in nonhematopoietic cells and preferentially required during early life. These results highlight the interplay between nonimmune and immune cells during Chikungunya virus infection and suggest an important role for nonhematopoietic cells as a critical source of IFN-α/ß.

Dietary phytochemicals induce p53- and caspase-independent cell death in human neuroblastoma cells.

Neuroblastoma (NB) is the most prevalent pediatric solid tumor and a leading cause of cancer-related death in children. In the present study, a novel cytotoxic role for the dietary compounds, curcumin, andrographolide, wedelolactone, dibenzoylmethane, and tanshinone IIA was identified in human S-type NB cells, SK-N-AS and SK-N-BE(2). Mechanistically, cell death appeared apoptotic by flow cytometry; however, these effects proceeded independently from both caspase-3 and p53 activation, as assessed by both genetic (shRNA) and pharmacological approaches. Notably, cell death induced by both curcumin and andrographolide was associated with decreased NFκB activity and a reduction in Bcl-2 and Bcl-xL expression. Finally, curcumin and andrographolide increased cytotoxicity following co-treatment with either cisplatin or doxorubicin, two chemotherapeutic agents widely used in the clinical management of NB. Coupled with the documented safety in humans, dietary compounds may represent a potential adjunct therapy for NB.

Astrocyte-derived glutathione attenuates hemin-induced apoptosis in cerebral microvascular cells.

Intracerebral hemorrhage (ICH) induces neurovascular injury via poorly defined mechanisms. The aim of this study was to determine whether gliovascular communication may restrict hemorrhagic vascular injury. Hemin, a hemoglobin by-product, concentration- and time-dependently increased apoptotic cell death in mouse bEnd.3 cells and in primary human brain microvascular endothelial cells, at least in part, via a caspase-3 dependent pathway. Cell death was preceded by a NFκB-mediated increase in inflammatory gene expression, including upregulation of inducible nitric oxide synthase (iNOS) expression and activity. Functionally, inhibition of iNOS or the addition of a peroxynitrite decomposition catalyst reduced cell death. Interestingly, co-treatment with astrocyte-conditioned media (ACM) reversed hemin-induced NFκB activation, nitrotyrosine formation, and apoptotic cell death, at least in part, via the release of the endogenous antioxidant, reduced glutathione (GSH). Prior treatment of astrocytes with the GSH-depleting agent, DL-buthionine (S,R)-sulfoximine or direct addition of diethyl maleate, a thiol-depleting agent, to ACM reversed the observed protection. In contrast, neither exogenous GSH nor the GSH precursor, N-acetylcysteine, was protective in bEnd.3 cells. Together, these data support an important role for astrocyte-derived GSH in the maintenance of oxidative balance in the vasculature and suggest therapeutic targeting of the GSH system may reduce neurological injury following ICH.

Hemin-induced necroptosis involves glutathione depletion in mouse astrocytes.

Intracerebral hemorrhage (ICH) is a devastating neurological injury associated with significant mortality. Astrocytic inflammation may contribute to the pathogenesis of ICH, although the underlying cellular mechanisms remain unclear. In this study, the hemoglobin oxidation by-product, hemin, concentration dependently induced necroptotic cell death in cortical astrocytes within 5 h of treatment. Hemin-induced cell death was preceded by increased inflammatory gene expression (COX-2, IL-1beta, TNF-alpha, iNOS). Inhibition of the NF-kappaB transcription factor reversed inflammatory gene expression and attenuated cell death after hemin treatment, suggesting a possible role for inflammatory mediators in astrocytic injury. Superoxide production paralleled the increase in iNOS expression, and inhibition of either iNOS (aminoguanidine or iminopiperdine) or superoxide (apocynin) significantly reduced cell death. Similarly, reduced formation of peroxynitrite, the damaging product of nitric oxide and superoxide, significantly reduced hemin injury. Hemin-induced peroxidative injury was associated with a rapid depletion of intracellular glutathione (GSH), culminating in lipid peroxidation and cell death, effects that were reduced by cotreatment with exogenous GSH, N-acetyl-L-cysteine, or the glutathione peroxidase mimetic ebselen. Together, these studies suggest a novel role for GSH depletion in necroptotic astrocyte injury after a hemorrhagic injury and indicate that therapeutic targeting of GSH may exert a beneficial effect after ICH.

Inhibition of NFkappaB reduces cellular viability in GH3 pituitary adenoma cells.

OBJECTIVE: Adenomas of the pituitary gland are among the most common types of tumors of the adult brain. Although adenomas are histologically benign, they may be associated with significant morbidity and mortality, mostly because of their invasive growth pattern and hormone hypersecretion. Current medical therapies are suppressive, acting at a receptor level. Thus, there is a need to identify novel cellular and molecular targets for pituitary tumors. We investigated the possible role of the NFkappaB transcription factor in pituitary tumor cell growth. METHODS: The effect of NFkappaB pathway inhibition on cellular viability was studied in the GH3 pituitary adenoma cell line, a well-characterized rat cell line that secretes growth hormone and prolactin. Cells were treated with mechanistically diverse pharmacological NFkappaB pathway inhibitors or with molecular inhibitors that were overexpressed in tumor cells before the assessment of cellular viability. NFkappaB activity was also assessed in GH3 cells using deoxyribonucleic acid binding assays. RESULTS: GH3 cells exhibited constitutive NFkappaB activity, which contributed to increased cellular proliferation. Treatment with wedelolactone, an IkappaB kinase inhibitor, or overexpression of an IkappaB super-repressor reduced cell viability, further implicating NFkappaB in pituitary tumor cell growth. Pharmacological or molecular inhibition of Akt similarly reduced GH3 viability and NFkappaB binding, suggesting that constitutive activation of NFkappaB may be, at least in part, mediated by Akt. CONCLUSION: Directed targeting of the Akt and NFkappaB signaling pathways may be a useful adjunct in the clinical management of pituitary tumors. Further elucidation of this pathway may yield novel information regarding the behavior of pituitary tumors in humans.

Infectivity and neutralization of simian immunodeficiency virus with FLAG epitope insertion in gp120 variable loops.

A FLAG epitope tag was substituted within variable loop 1 (V1), 2 (V2), or 4 (V4) of the gp120 envelope glycoprotein of simian immunodeficiency virus strain 239 (SIV239) to evaluate the extent to which each variable loop may serve as a target for antibody-mediated neutralization. Two sites within each variable loop of SIV239 were chosen for individual epitope tag insertions. FLAG epitope substitutions were also made in the V1, V2, and V4 loops of a neutralization-sensitive derivative of SIV239, SIV316. Of the 10 FLAG-tagged recombinant viruses analyzed, three (SIV239FV1b, SIV239FV2b, and SIV239FV4a) replicated with kinetics similar to those of the parental strain, SIV239, in both CEMx174 cells and the immortalized rhesus monkey T-cell line 221. The SIV316FV1b and SIV316FV4a FLAG variants replicated with a substantial lag, and the five remaining recombinants did not replicate detectably. Both gp160 and gp120 from replication-competent FLAG variants could be immunoprecipitated from transfected 293T cells by the anti-gp120 rhesus monoclonal antibody (RhMAb) 3.11H, the anti-FLAG MAb M2, and CD4-immunoglobulin, whereas only unprocessed gp160 was detected in 293T cells transfected with replication-defective variants. Furthermore, gp120 was detectably incorporated only into virions that were infectious. SIV239FV1b was sensitive to neutralization by MAb M2, with a 50% inhibitory concentration of 1 mug/ml. Neither SIV239FV2b nor SIV239FV4a was sensitive to M2 neutralization. The ability of the M2 antibody to neutralize SIV239FV1b infectivity was associated with an increased ability of the M2 antibody to detect native, oligomeric SIV239FV1b envelope protein on the surfaces of cells relative to that for the other SIV FLAG variants. Furthermore, SIV239FV1b was globally more sensitive to antibody-mediated neutralization than was parental SIV239 when these strains were screened with a panel of anti-SIV MAbs of various specificities. These results indicate that the V1 loop can serve as an effective target for neutralization on SIV239FV1b. However, antibody-mediated neutralization of this variant, similar to that of other SIV239 variants that have been studied previously, was associated with a global increase in neutralization sensitivity. These results suggest that the variable loops on the neutralization-resistant SIV239 strain are difficult for antibodies to access effectively and that mutations that allow neutralization have global effects on the trimeric envelope glycoprotein structure and accessibility.