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Dive into the research topics where Bahri Karacay is active.

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Featured researches published by Bahri Karacay.


Journal of Immunology | 2001

Selective Gene Expression and Activation-Dependent Regulation of Vasoactive Intestinal Peptide Receptor Type 1 and Type 2 in Human T Cells

Maria L. Lara-Marquez; M. Sue O’Dorisio; Thomas M. O’Dorisio; Manisha H. Shah; Bahri Karacay

Vasoactive intestinal peptide (VIP) has potent antiproliferative and anti-inflammatory functions in the immune system. Two structurally distinct G-protein-associated receptors, VIP receptor type 1 (VPAC1) and VIP receptor type 2 (VPAC2), mediate the biological effects of VIP. The regulation of VIP receptor gene expression and the distribution of these receptors in different compartments of the human immune systems are unknown. This study reports, for the first time, a quantitative analysis of VPAC1 and VPAC2 mRNA expression in resting and activated T cells as well as in resting monocytes. Purified human peripheral blood CD4+ T cells and CD8+ T cells were stimulated via the TCR/CD3 receptor complex. Using the novel fluorometric-based kinetic (real-time) RT-PCR, we determined that VPAC1 is constitutively expressed in resting T cells and monocytes; the levels of expression were significantly higher in monocytes and CD4+ T cells than in CD8+ T cells. VPAC1 mRNA expression is significantly higher relative to VPAC2 in resting CD4+ T cells and CD8+ T cells. VPAC2 is expressed at very low levels in resting T cells but is not detectable in resting monocytes. In vitro stimulation of Th cells with soluble anti-CD3 plus PMA induced a T cell activation-dependent down-regulation of VPAC1. VPAC1 is down-regulated under conditions of optimal T cell stimulation. Our results suggest that selective VIP effects on T cell function may be mediated via selective expression of VPAC1 and VPAC2 on T cells and monocytes. Furthermore, down-regulation of VPAC1 in CD4+ T cell subpopulations is highly correlated with T cell activation.


Developmental Brain Research | 2003

FGF-2, NGF and IGF-1, but not BDNF, utilize a nitric oxide pathway to signal neurotrophic and neuroprotective effects against alcohol toxicity in cerebellar granule cell cultures

Daniel J. Bonthius; Bahri Karacay; De Dai; Nicholas J. Pantazis

Neuronal death is a prominent neuropathological component of fetal alcohol syndrome (FAS). Identification of molecular agents and pathways that can ameliorate alcohol-induced cell loss offers possible therapeutic strategies for FAS and potential insight into its pathogenesis. This study investigated the effects of growth factors on cellular survival in alcohol-exposed cerebellar granule cell (CGC) cultures and examined the role of the nitric oxide (NO)-cGMP-PKG (cGMP-dependent protein kinase) pathway in the cell survival-promoting effects of these growth factors. Primary CGC cultures were exposed to 0 or 400 mg/dl ethanol, accompanied by either no growth factor or 30 ng/ml fibroblast growth factor-2 (FGF-2), nerve growth factor (NGF), insulin-like growth factor-1 (IGF-1), brain-derived neurotrophic factor (BDNF) or epidermal growth factor (EGF). Viable neurons were quantified after 1 day of exposure. Two distinct types of cell survival-promoting effects of growth factors were detectable: (1) a neurotrophic effect, in which the growth factors diminished the background death of neurons that occurred in alcohol-free cultures; and (2) a neuroprotective effect, in which the growth factors diminished alcohol-induced cell death. The various growth factors differed markedly in their patterns of cell survival promotion. While BDNF and FGF-2 exerted both a neurotrophic and a neuroprotective effect, IGF-1 had only a neurotrophic effect and did not protect against alcohol toxicity, and NGF had only a neuroprotective effect and did not diminish background cell death. EGF had neither a neurotrophic nor a neuroprotective effect. In order to determine the role of the NO-cGMP-PKG pathway in the cell survival-promoting effects mediated by growth factors, cultures were exposed to one of several pharmacological inhibitors of the pathway, including NAME, LY83583 and PKG inhibitor. The cell survival-promoting effects of FGF-2, NGF and IGF-1 were all substantially reduced by each of the pathway inhibitors. In contrast, neither the neurotrophic nor the neuroprotective effects of BDNF were altered by any of the pathway inhibitors. Thus, growth factors differ in their patterns of neurotrophic and neuroprotective effects, and they differ in their reliance on the NO-cGMP-PKG pathway. While FGF-2, NGF and IGF-1 all signal their survival-promoting effects through the NO-cGMP-PKG pathway, BDNF does not rely upon this pathway for signal transduction in CGC cultures.


Annals of Neurology | 2007

Congenital lymphocytic choriomeningitis virus infection : Spectrum of disease

Daniel J. Bonthius; Rhonda Wright; Brian Tseng; Leslie L. Barton; Elysa J. Marco; Bahri Karacay; Paul D. Larsen

Lymphocytic choriomeningitis virus (LCMV) is a human pathogen and an emerging neuroteratogen. When the infection occurs during pregnancy, the virus can target and damage the fetal brain and retina. We examined the spectrum of clinical presentations, neuroimaging findings, and clinical outcomes of children with congenital LCMV infection.


Cancer Biology & Therapy | 2005

Histone deacetylase inhibitors modulate renal cell carcinoma sensitivity to TRAIL/Apo-2L-induced apoptosis by enhancing TRAIL-R2 expression

Rebecca L. VanOosten; Jill M. Moore; Bahri Karacay; Thomas S. Griffith

Every year, 12,000 people in the U.S. die from renal cell carcinoma. Current therapies include partial or complete nephrectomy or treatments such as administration of IFN-? and/or interleukins that are moderately effective, at best. Moreover, the current therapies are invasive and inefficient and new therapies are needed. Histone deacetylase (HDAC) inhibitors have recently been found to sensitize cells to apoptosis-inducing agents, although the mechanism of this action is largely unknown. The current study has investigated the potential of using five different histone deacetylase inhibitors (HDACI) (depsipeptide, MS-275, oxamflatin, sodium butyrate, and trichostatin A) to sensitize TNF-related apoptosis-inducing ligand (TRAIL)/Apo-2L-resistant renal cell carcinoma cells to TRAIL/Apo-2L-induced apoptosis. Sodium butyrate and trichostatin A each enhanced TRAIL/Apo-2L-mediated tumor cell death to a greater extent than the other HDACI. Annexin V staining and caspase activity demonstrated the mechanism of cell death was apoptosis. Both sodium butyrate and trichostatin A treatment also increased mRNA and surface expression of TRAIL receptor 2 that was dependent on the transcription factor Sp1, thus providing a possible mechanism behind the increased sensitivity to TRAIL/Apo-2L. These results indicate that combination therapy of HDACI, such as sodium butyrate and trichostatin A, and TRAIL/Apo-2L has great potential for an efficient alternative therapy for renal cell carcinoma.


Developmental Brain Research | 2002

Deficiency of neuronal nitric oxide synthase (nNOS) worsens alcohol-induced microencephaly and neuronal loss in developing mice.

Daniel J. Bonthius; Georgios Tzouras; Bahri Karacay; Jolonda C. Mahoney; Ana Hutton; Ross McKim; Nicholas J. Pantazis

Previous work conducted in vitro suggests that nitric oxide (NO) protects developing neurons against the toxic effects of alcohol. We tested the hypothesis that neonatal mice carrying a null mutation for neuronal nitric oxide synthase (nNOS), the enzyme which synthesizes NO in neurons, have increased vulnerability to alcohol-induced microencephaly and neuronal loss. Wild-type mice and mutant (nNOS(-/-)) mice received a single intraperitoneal injection of ethanol (0.0, 2.2, 3.3, or 4.4 g/kg) daily over postnatal days (PD) 4-9 and were sacrificed on PD 10. Peak blood alcohol concentrations were approximately 170, 280, and 385 mg/dl for the 2.2, 3.3 and 4.4 g/kg/day treatment groups, respectively, and did not differ significantly between wild-type and nNOS(-/-) strains. Exposure to alcohol induced dose-dependent reductions in total brain weight, forebrain weight and cerebellum weight in both strains of mice. However, the reductions in brain weight were significantly more severe in the nNOS(-/-) mice than in wild type. Quantification of cerebellar neurons revealed that alcohol-induced losses of Purkinje cells and granule cells were both significantly greater in the nNOS(-/-) mice than in wild type. The increased vulnerability of nNOS-deficient neurons to alcohol-induced cell death was confirmed in vitro. Cerebellar granule cell cultures derived from nNOS(-/-) and wild-type mice were exposed for 24 h to 0, 100, 200 or 400 mg/dl ethanol. At each alcohol concentration, the nNOS(-/-) neurons had a significantly greater cell loss than did the wild-type neurons. The results demonstrate that deficiency of nNOS decreases the ability of developing neurons to survive the toxic effects of alcohol. Because NO upregulates intracellular cGMP, which can activate cGMP-dependent protein kinase (PKG), we hypothesize that the NO-cGMP-PKG pathway has a neuroprotective role against alcohol toxicity within the developing brain.


Cancer Gene Therapy | 2004

Inhibition of the NF- κ B pathway enhances TRAIL-mediated apoptosis in neuroblastoma cells

Bahri Karacay; Salih Sanlioglu; Thomas S. Griffith; Anthony D. Sandler; Daniel J. Bonthius

Neuroblastoma is the most common solid extracranial neoplasm in children and causes many deaths. Despite treatment advances, prognosis for neuroblastoma remains poor, and a critical need exists for the development of new treatment regimens. TNF-related apoptosis-inducing-ligand (TRAIL) induces cell death in a variety of tumors, but not in normal tissues. Moreover, TRAIL is nontoxic, making it a strong antitumor therapeutic candidate. We demonstrate that introduction of the TRAIL gene into neuroblastoma cell lines using an adenoviral vector leads to apoptotic cell death. RT-PCR and flow-cytometric analyses demonstrated that TRAILs effect is mediated primarily via the TRAIL R2 receptor. As TRAIL can activate the nuclear factor-κB (NF-κB) signaling pathway, which can exert an antiapoptotic effect, we hypothesized that inhibition of NF-κB signaling may augment TRAILs killing effects. TRAIL-mediated cell death was enhanced when neuroblastoma cells were simultaneously infected with a dominant-negative mutant of IκB kinase, a kinase essential for NF-κB activation. The combination of blockade of NF-κB signaling and expression of TRAIL induced apoptotic death in a greater proportion of SKNSH cells than did either treatment alone. Thus, concurrent inhibition of the NF-κB pathway and the induction of TRAIL-mediated apoptosis may become a useful approach for the treatment of neuroblastoma.


Cancer Gene Therapy | 2006

Adenovirus-mediated IKKbetaKA expression sensitizes prostate carcinoma cells to TRAIL-induced apoptosis.

Ahter Dilsad Sanlioglu; Ismail Turker Koksal; Bahri Karacay; M Baykara; Guven Luleci; Salih Sanlioglu

Despite the fact that tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) can selectively induce apoptosis in cancer cells, TRAIL resistance in cancer cells has challenged the use of TRAIL as a therapeutic agent. First, prostate carcinoma cell lines (DU145, LNCaP and PC3) were screened for sensitivity to adenovirus delivery of TRAIL (Ad5hTRAIL). As amplified Ikappa B kinase (IKK) activity is responsible for the constitutive nuclear factor-κB (NF-κB) activation leading to uncontrolled cell growth and metastasis, a dual vector approach using both an adenovirus vector (Ad) expressing the dominant-negative mutant of IKKβ (AdIKKβKA) and Ad5hTRAIL was employed to determine if prostate cancer cells were sensitized to TRAIL in the setting of IKK inhibition. Inhibition of the NF-κB pathway through IKK blockade sensitized all three prostate cancer cell lines to TRAIL, regardless of NF-κB activation or decoy receptor gene expression. Moreover, a novel quantitative real-time RT-PCR assay and conventional flow cytometry analysis indicated that TRAIL-resistant DU145 and LNCaP cells, but not TRAIL-sensitive PC3 cells, expressed substantial amounts of TRAIL Decoy Receptor 4. In conclusion, TRAIL decoy receptor expression appeared to be the chief determinant of TRAIL resistance encountered in prostate carcinoma cell lines.


Cancer Gene Therapy | 2007

DcR2 (TRAIL-R4) siRNA and adenovirus delivery of TRAIL (Ad5hTRAIL) break down in vitro tumorigenic potential of prostate carcinoma cells.

Ahter Dilsad Sanlioglu; Bahri Karacay; Ismail Turker Koksal; Thomas S. Griffith; Salih Sanlioglu

High levels of decoy receptor 2 (DcR2; TRAIL-R4) expression are correlated with TRAIL resistance in prostate cancer cells. In addition, upregulation of TRAIL death receptor (DR4 and DR5) expression, either by ionizing radiation or chemotherapy, can sensitize cancer cells to TRAIL. Considering more than half of human cancers are TRAIL resistant, modulation of surface TRAIL receptor expression appears to be an attractive treatment modality to counteract TRAIL resistance. In this study, three siRNA duplexes targeting DcR2 receptor were tested. Ad5hTRAIL infections were performed to overexpress human full-length TRAIL to induce cell death, and the in vitro tumorigenic potential of prostate cancer cells was assessed using colony-forming assays on soft agar. The DU145 and LNCaP prostate cancer cell lines, which express high levels of DcR2, were resistant to Ad5hTRAIL-induced death. Downregulation of surface DcR2 expression by siRNA sensitized these prostate cancer cell lines to Ad5hTRAIL. In addition, DcR2 siRNA-mediated knockdown of DcR2, followed by Ad5hTRAIL infection, dramatically reduced the in vitro tumorigenic potential of prostate cancer cells. Collectively, our results suggest the potential for combining receptor-specific siRNA with TRAIL in the treatment of certain cancers.


Neurotoxicology | 2008

The protective effect of neuronal nitric oxide synthase (nNOS) against alcohol toxicity depends upon the NO-cGMP-PKG pathway and NF-κB

Daniel J. Bonthius; Nancy E. Bonthius; Shenglan Li; Bahri Karacay

Fetal alcohol syndrome (FAS) stems from maternal alcohol abuse during pregnancy and is an important cause of mental retardation and hyperactivity in children. In the developing brain, alcohol can kill neurons, leading to microencephaly. However, due to their genetic makeup, some individuals are less vulnerable than others to alcohols neurotoxic effects. Animal studies have demonstrated that one particular gene, neuronal nitric oxide synthase (nNOS), protects developing neurons in vivo against alcohol-induced death. We utilized pharmacologic techniques to demonstrate that nNOS protects neurons against alcohol toxicity by activating the NO-cGMP-PKG signaling pathway. Cerebellar granule cell cultures derived from mice carrying a null mutation for nNOS (nNOS-/- mice) were substantially more vulnerable than cultures from wild-type mice to alcohol-induced cell death. However, activation of the pathway at sites downstream of nNOS protected the cultures against alcohol toxicity. Conversely, blockade of the pathway rendered wild-type cultures vulnerable to alcohol-induced death. We further identified NF-kappaB as the downstream effector through which nNOS and the NO-cGMP-PKG pathway signal their neuroprotective effects. Tumor necrosis factor-alpha (TNF-alpha), which activates NF-kappaB, ameliorated alcohol-induced cell death in nNOS-/- and wild-type cultures, while an NF-kappaB inhibitor (NFi) blocked the protective effects of TNF-alpha and worsened alcohol-induced cell death. Furthermore, NFi blocked the protective effects of NO-cGMP-PKG pathway activators, demonstrating that NF-kappaB is downstream of the NO-cGMP-PKG pathway. As wild-type neurons matured in culture, they became resistant to alcohol toxicity. However, this maturation-dependent alcohol resistance did not occur in nNOS-/- mice and could be reversed in wild-type mice with NFi, demonstrating that nitric oxide and NF-kappaB are crucial for the development of alcohol resistance with age. Thus, nNOS protects developing neurons against alcohol toxicity by activating the NO-cGMP-PKG-NF-kappaB pathway and is crucial for the acquisition of maturation-dependent alcohol resistance.


Journal of Virology | 2002

Critical Role for Glial Cells in the Propagation and Spread of Lymphocytic Choriomeningitis Virus in the Developing Rat Brain

Daniel J. Bonthius; Jolonda C. Mahoney; Michael J. Buchmeier; Bahri Karacay; Derek A. Taggard

ABSTRACT Inoculation of the neonatal rat with lymphocytic choriomeningitis virus (LCMV) results in the selective infection of several neuronal populations and in focal pathological changes. However, the pathway by which LCMV reaches the susceptible neurons has not been described, and the nature and time course of the pathological changes induced by the infection are largely unknown. This study examined the sequential migration of LCMV in the developing rat brain and compared the pathological changes among infected brain regions. The results demonstrate that astrocytes and Bergmann glia cells are the first cells of the brain parenchyma infected with LCMV and that the virus spreads across the brain principally via contiguous glial cells. The virus then spreads from glial cells into neurons. However, not all neurons are susceptible to infection. LCMV infects neurons in only four specific brain regions: the cerebellum, olfactory bulb, dentate gyrus, and periventricular region. The virus is then cleared from glial cells but persists in neurons. LCMV induces markedly different pathological changes in each of the four infected regions. The cerebellum undergoes an acute and permanent destruction, while the olfactory bulb is acutely hypoplastic but recovers fully with age. Neurons of the dentate gyrus are unaffected in the acute phase but undergo a delayed-onset mortality. In contrast, the periventricular region has neither acute nor late-onset cell loss. Thus, LCMV infects four specific brain regions in the developing brain by spreading from glial cells to neurons and then induces substantially different pathological changes with diverse time courses in each of the four infected regions.

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