Ariel Martínez - Academia.edu (original) (raw)

Papers by Ariel Martínez

Research paper thumbnail of Nearly identical strains of human herpesvirus 8 in couples discordant for Kaposiʼs sarcoma

Aids, 2007

Control and Prevention stages B or C (42% in each group). The median plasma HIV-1-RNA level was 1... more Control and Prevention stages B or C (42% in each group). The median plasma HIV-1-RNA level was 104 736 copies/ml [interquartile range (IQR) 40 804-243 787] and the median CD4 cell count was 118 Â 10 6 cells/l (IQR 78-167).

Research paper thumbnail of RANK ligand and interferon gamma differentially regulate cathepsin gene expression in pre-osteoclastic cells

Biochemical and Biophysical Research Communications, 2005

Receptor activator of NF-jB ligand (RANKL) and interferon gamma (IFN-c) are critical and opposing... more Receptor activator of NF-jB ligand (RANKL) and interferon gamma (IFN-c) are critical and opposing mediators of osteoclastogenesis, exerting stimulatory and inhibitory effects, respectively. Cathepsin K (CTSK) is a secreted protease that plays an essential role in osteoclastic bone resorption. We have examined the role of IFN-c in the regulation of CTSK expression in the murine monocytic RAW 264.7 cell line, which can be readily differentiated to bone-resorbing osteoclasts upon RANKL treatment. Realtime RT-PCR reveals that RANKL stimulates CTSK mRNA expression in a dose-and time-dependent fashion, but that RANKL does not alter the expression of cathepsin L (CTSL) and cathepsin S (CTSS) mRNA. IFN-c stimulates both CTSL and CTSS expression after 3 days, but fails to significantly alter CTSK expression. IFN-c markedly inhibits the stimulation of CTSK mRNA and protein by RANKL, whereas RANKL suppresses the stimulation of CTSL and CTSS mRNA by IFN-c. IFN-c also ablates the RANKL induced osteoclastic differentiation of RAW cells. In RAW cells stably transfected with a CTSK promoter-luciferase plasmid containing the 1618 bp upstream of the transcription initiation site, IFN-c inhibits CTSK promoter activity and ablates its induction by RANKL. In conclusion, IFN-c and RANKL differentially regulate cathepsin K, S, and L gene expression in pre-osteoclastic cells, and there appears to be significant cross talk between the signal transduction pathways mediating the responses to RANKL and IFN-c. Published by Elsevier Inc.

Research paper thumbnail of AP1 stimulates the cathepsin K promoter in RAW 264.7 cells

Gene, 2007

Cathepsin K (CTSK) is a secreted protease that plays an essential role in osteoclastic bone resor... more Cathepsin K (CTSK) is a secreted protease that plays an essential role in osteoclastic bone resorption, and CTSK levels increase with osteoclast differentiation and activation, a process that is controlled by a complex physiological network of hormones and cytokines. A critical regulator of this process is receptor activator of NF-κB ligand (RANKL), a member of the tumor necrosis factor (TNF) superfamily of cytokines that can act via the TNF receptor activating factor (TRAF6)/AP-1 signaling pathway. However, the mechanism whereby RANKL modulates CTSK expression is not fully understood. Therefore, we investigated the regulation of CTSK expression and promoter activity in RAW 264.7 osteoclast precursor cells, which can be readily differentiated to osteoclasts upon RANKL stimulation. Western blot analysis, real-time RT-PCR and luciferase reporter gene assays revealed that RANKL stimulated CTSK expression and promoter activity in a dose-and time-dependent manner and that this activation was inhibited by either dominant negative (DN) TRAF6 or DN-c-fos. TRAF6 stimulated the basal activity of a truncated CTSK promoter, and DN-c-fos blocked this stimulation. JunB alone also stimulated basal CTSK promoter activity, whereas c-jun, JunD or c-fos alone did not. However, co-transfection of any of these jun-family members with c-fos (AP-1) significantly increased CTSK promoter expression. siRNA targeted against c-jun or junB suppressed RANKL-mediated CTSK expression. Therefore, both TRAF6 and AP-1 help regulate the basal and RANKL-mediated stimulation of CTSK gene expression in RAW 264.7 cells.

Research paper thumbnail of Molecular epidemiology of Kaposi's sarcoma herpesvirus (KSHV) in Cuban and German patients with Kaposi's sarcoma (KS) and asymptomatic sexual contacts

Virology, 2005

Kaposi's sarcoma (KS) shows a distinct geographical and ethnic distribution. The variable K1 gene... more Kaposi's sarcoma (KS) shows a distinct geographical and ethnic distribution. The variable K1 gene serves to differentiate the KSHV subtypes A -E, M, N, and Q. Phylogenetic characterization of 19 classical and epidemic German KS specimens revealed the Eurasian KSHV subtypes C (n = 13, including 6 classical KS) and A (n = 6), while 27 Cuban specimens showed a variety of different subtypes (A: n = 16, 4 being A5; C: n = 8; B: n = 2; and the new subtype E: n = 1). Three pairs of isolates from KS patients and peripheral blood mononuclear cells (PBMC) of their sexual partners without KS were studied for the first time and found identical, strongly arguing for sexual transmission of KSHV in this unique cohort. The unique ethnic background of the Cuban population may explain the variety of different KSHV strains. D

Research paper thumbnail of Identification of NFAT binding sites that mediate stimulation of cathepsin K promoter activity by RANK ligand

Gene, 2009

The receptor activator of NFκB ligand (RANKL) is a critical mediator of osteoclastogenesis and re... more The receptor activator of NFκB ligand (RANKL) is a critical mediator of osteoclastogenesis and regulates cathepsin K (CTSK) expression, which is essential for normal bone resorption. RANKL acts, in part, via the Ca 2+ / calmodulin/calcineurin signaling pathway, which in turn, activates NFATc1 (nuclear factor of activated T-cells) and downstream gene expression. We investigated the signals and promoter elements that regulate CTSK gene expression in RAW 264.7 cells, which can be differentiated to osteoclasts by RANKL. Disrupting Ca 2+ signaling, by blocking Ca 2+ channels, thus inhibiting calcineurin or chelation of intracellular Ca 2+ , prevented the stimulation of CTSK expression by RANKL. Both RANKL treatment and overexpression of NFATc1 dramatically enhanced CTSK promoter activity, but not in an identical manner. NFATc1 regulates CTSK promoter activity, but the motifs have not been explicitly identified. We found that as few as 238 bp of the CTSK promoter were sufficient to elicit a marked response to both RANKL and NFATc1, truncations of the CTSK promoter illustrated differences in regional responsiveness. Transfection analysis of CTSK promoter-luciferase plasmids revealed that NFATc1 binding sites at 85, 289 and 345 bp upstream of the transcriptional start site mediated responses to RANKL and NFATc1. Deletion of a 4-bp core element from the site at −85 bp dramatically reduced the response of the CTSK promoter to both RANKL and NFATc1, whereas a similar deletion at −345 bp decreased NFATc1-but not RANKL-mediated responses. Mutation of the site at −289 bp did not affect NFAT-mediated stimulation of CTSK on its own, but did decrease responsiveness in combination with either or both of the other two deletions. Electrophoretic mobility shift assays demonstrated NFATc1 binding to oligonucleotides containing the −85-bp and −345-bp sites, while chromatin immunoprecipitation assays demonstrated enhanced in situ binding by NFATc1 to two analogous sites in the mouse CTSK promoter in response to RANKL treatment. Therefore, proximal NFAT binding sites play a significant role in the NFATc1-mediated stimulation of CTSK gene expression by RANKL.

Research paper thumbnail of Pharmacogenetic Impact of VKORC1 and CYP2C9 Allelic Variants on Warfarin Dose Requirements in a Hispanic Population Isolate

Clinical and Applied Thrombosis-hemostasis, 2010

Warfarin is the most prescribed oral anticoagulant worldwide. Because of the complexity of warfar... more Warfarin is the most prescribed oral anticoagulant worldwide. Because of the complexity of warfarin therapy, we attempted to dissect genetic from bioenvironmental factors influencing warfarin dose responses in individuals of a genetic isolate of Hispanic ancestry. A total of 191 patients with standard values of international normalized ratio were recruited. Three groups with a significantly different warfarin dose response were identified, that is, sensitive (2.28 + 0.50 mg/d), intermediate (4.2 + 0.76 mg/d), and resistant (7.40 + 1.54 mg/d; Tukey test, P < .001). Age had a significant inverse correlation with warfarin dose (P < .001; effective dose diminished 0.56 mg/d/decade). Required doses were higher for individuals with CYP2C9 variants containing the allele *1 compared to those individuals with variants composed of other alleles (P ¼ .006). Similarly, individuals with VKORC1-1639GG and VKORC1-1639GA genotypes also required higher doses compared to the AA genotype (P < .001). Evaluation of potential gene-gene interactions between CYP2C9 and VKORC1 polymorphisms showed significant differences in dosing for CYP2C9 genotypes within the VKORC1-1639G/A subgroup (P ¼ .013). A stepwise multivariate linear regression analysis showed that 38.2% of the warfarin dose response variance was accounted for by a model involving age (20.9%), VKORC1-1639G/A (11.3%), and CYP2C9*1, *2, and *3 variants (7.1%). These results corroborate previous findings on warfarin pharmacogenetics and define a contrastable gene-bioenvironment interaction model suited to be used in Hispanic populations.

Research paper thumbnail of Potential cognitive endophenotypes in multigenerational families: segregating ADHD from a genetic isolate

Adhd Attention Deficit and Hyperactivity Disorders

Endophenotypes are neurobiological markers cosegregating and associated with illness. These bioma... more Endophenotypes are neurobiological markers cosegregating and associated with illness. These biomarkers represent a promising strategy to dissect ADHD biological causes. This study was aimed at contrasting the genetics of neuropsychological tasks for intelligence, attention, memory, visual-motor skills, and executive function in children from multigenerational and extended pedigrees that cluster ADHD in a genetic isolate. In a sample of 288 children and adolescents, 194 (67.4%) ADHD affected and 94 (32.6%) unaffected, a battery of neuropsychological tests was utilized to assess the association between genetic transmission and the ADHD phenotype. We found significant differences between affected and unaffected children in the WISC block design, PIQ and FSIQ, continuous vigilance, and visual-motor skills, and these variables exhibited a significant heritability. Given the association between these neuropsychological variables and ADHD, and also the high genetic component underlying their transmission in the studied pedigrees, we suggest that these variables be considered as potential cognitive endophenotypes suitable as quantitative trait loci (QTLs) in future studies of linkage and association.

Research paper thumbnail of Nearly identical strains of human herpesvirus 8 in couples discordant for Kaposiʼs sarcoma

Aids, 2007

Control and Prevention stages B or C (42% in each group). The median plasma HIV-1-RNA level was 1... more Control and Prevention stages B or C (42% in each group). The median plasma HIV-1-RNA level was 104 736 copies/ml [interquartile range (IQR) 40 804-243 787] and the median CD4 cell count was 118 Â 10 6 cells/l (IQR 78-167).

Research paper thumbnail of RANK ligand and interferon gamma differentially regulate cathepsin gene expression in pre-osteoclastic cells

Biochemical and Biophysical Research Communications, 2005

Receptor activator of NF-jB ligand (RANKL) and interferon gamma (IFN-c) are critical and opposing... more Receptor activator of NF-jB ligand (RANKL) and interferon gamma (IFN-c) are critical and opposing mediators of osteoclastogenesis, exerting stimulatory and inhibitory effects, respectively. Cathepsin K (CTSK) is a secreted protease that plays an essential role in osteoclastic bone resorption. We have examined the role of IFN-c in the regulation of CTSK expression in the murine monocytic RAW 264.7 cell line, which can be readily differentiated to bone-resorbing osteoclasts upon RANKL treatment. Realtime RT-PCR reveals that RANKL stimulates CTSK mRNA expression in a dose-and time-dependent fashion, but that RANKL does not alter the expression of cathepsin L (CTSL) and cathepsin S (CTSS) mRNA. IFN-c stimulates both CTSL and CTSS expression after 3 days, but fails to significantly alter CTSK expression. IFN-c markedly inhibits the stimulation of CTSK mRNA and protein by RANKL, whereas RANKL suppresses the stimulation of CTSL and CTSS mRNA by IFN-c. IFN-c also ablates the RANKL induced osteoclastic differentiation of RAW cells. In RAW cells stably transfected with a CTSK promoter-luciferase plasmid containing the 1618 bp upstream of the transcription initiation site, IFN-c inhibits CTSK promoter activity and ablates its induction by RANKL. In conclusion, IFN-c and RANKL differentially regulate cathepsin K, S, and L gene expression in pre-osteoclastic cells, and there appears to be significant cross talk between the signal transduction pathways mediating the responses to RANKL and IFN-c. Published by Elsevier Inc.

Research paper thumbnail of AP1 stimulates the cathepsin K promoter in RAW 264.7 cells

Gene, 2007

Cathepsin K (CTSK) is a secreted protease that plays an essential role in osteoclastic bone resor... more Cathepsin K (CTSK) is a secreted protease that plays an essential role in osteoclastic bone resorption, and CTSK levels increase with osteoclast differentiation and activation, a process that is controlled by a complex physiological network of hormones and cytokines. A critical regulator of this process is receptor activator of NF-κB ligand (RANKL), a member of the tumor necrosis factor (TNF) superfamily of cytokines that can act via the TNF receptor activating factor (TRAF6)/AP-1 signaling pathway. However, the mechanism whereby RANKL modulates CTSK expression is not fully understood. Therefore, we investigated the regulation of CTSK expression and promoter activity in RAW 264.7 osteoclast precursor cells, which can be readily differentiated to osteoclasts upon RANKL stimulation. Western blot analysis, real-time RT-PCR and luciferase reporter gene assays revealed that RANKL stimulated CTSK expression and promoter activity in a dose-and time-dependent manner and that this activation was inhibited by either dominant negative (DN) TRAF6 or DN-c-fos. TRAF6 stimulated the basal activity of a truncated CTSK promoter, and DN-c-fos blocked this stimulation. JunB alone also stimulated basal CTSK promoter activity, whereas c-jun, JunD or c-fos alone did not. However, co-transfection of any of these jun-family members with c-fos (AP-1) significantly increased CTSK promoter expression. siRNA targeted against c-jun or junB suppressed RANKL-mediated CTSK expression. Therefore, both TRAF6 and AP-1 help regulate the basal and RANKL-mediated stimulation of CTSK gene expression in RAW 264.7 cells.

Research paper thumbnail of Molecular epidemiology of Kaposi's sarcoma herpesvirus (KSHV) in Cuban and German patients with Kaposi's sarcoma (KS) and asymptomatic sexual contacts

Virology, 2005

Kaposi's sarcoma (KS) shows a distinct geographical and ethnic distribution. The variable K1 gene... more Kaposi's sarcoma (KS) shows a distinct geographical and ethnic distribution. The variable K1 gene serves to differentiate the KSHV subtypes A -E, M, N, and Q. Phylogenetic characterization of 19 classical and epidemic German KS specimens revealed the Eurasian KSHV subtypes C (n = 13, including 6 classical KS) and A (n = 6), while 27 Cuban specimens showed a variety of different subtypes (A: n = 16, 4 being A5; C: n = 8; B: n = 2; and the new subtype E: n = 1). Three pairs of isolates from KS patients and peripheral blood mononuclear cells (PBMC) of their sexual partners without KS were studied for the first time and found identical, strongly arguing for sexual transmission of KSHV in this unique cohort. The unique ethnic background of the Cuban population may explain the variety of different KSHV strains. D

Research paper thumbnail of Identification of NFAT binding sites that mediate stimulation of cathepsin K promoter activity by RANK ligand

Gene, 2009

The receptor activator of NFκB ligand (RANKL) is a critical mediator of osteoclastogenesis and re... more The receptor activator of NFκB ligand (RANKL) is a critical mediator of osteoclastogenesis and regulates cathepsin K (CTSK) expression, which is essential for normal bone resorption. RANKL acts, in part, via the Ca 2+ / calmodulin/calcineurin signaling pathway, which in turn, activates NFATc1 (nuclear factor of activated T-cells) and downstream gene expression. We investigated the signals and promoter elements that regulate CTSK gene expression in RAW 264.7 cells, which can be differentiated to osteoclasts by RANKL. Disrupting Ca 2+ signaling, by blocking Ca 2+ channels, thus inhibiting calcineurin or chelation of intracellular Ca 2+ , prevented the stimulation of CTSK expression by RANKL. Both RANKL treatment and overexpression of NFATc1 dramatically enhanced CTSK promoter activity, but not in an identical manner. NFATc1 regulates CTSK promoter activity, but the motifs have not been explicitly identified. We found that as few as 238 bp of the CTSK promoter were sufficient to elicit a marked response to both RANKL and NFATc1, truncations of the CTSK promoter illustrated differences in regional responsiveness. Transfection analysis of CTSK promoter-luciferase plasmids revealed that NFATc1 binding sites at 85, 289 and 345 bp upstream of the transcriptional start site mediated responses to RANKL and NFATc1. Deletion of a 4-bp core element from the site at −85 bp dramatically reduced the response of the CTSK promoter to both RANKL and NFATc1, whereas a similar deletion at −345 bp decreased NFATc1-but not RANKL-mediated responses. Mutation of the site at −289 bp did not affect NFAT-mediated stimulation of CTSK on its own, but did decrease responsiveness in combination with either or both of the other two deletions. Electrophoretic mobility shift assays demonstrated NFATc1 binding to oligonucleotides containing the −85-bp and −345-bp sites, while chromatin immunoprecipitation assays demonstrated enhanced in situ binding by NFATc1 to two analogous sites in the mouse CTSK promoter in response to RANKL treatment. Therefore, proximal NFAT binding sites play a significant role in the NFATc1-mediated stimulation of CTSK gene expression by RANKL.

Research paper thumbnail of Pharmacogenetic Impact of VKORC1 and CYP2C9 Allelic Variants on Warfarin Dose Requirements in a Hispanic Population Isolate

Clinical and Applied Thrombosis-hemostasis, 2010

Warfarin is the most prescribed oral anticoagulant worldwide. Because of the complexity of warfar... more Warfarin is the most prescribed oral anticoagulant worldwide. Because of the complexity of warfarin therapy, we attempted to dissect genetic from bioenvironmental factors influencing warfarin dose responses in individuals of a genetic isolate of Hispanic ancestry. A total of 191 patients with standard values of international normalized ratio were recruited. Three groups with a significantly different warfarin dose response were identified, that is, sensitive (2.28 + 0.50 mg/d), intermediate (4.2 + 0.76 mg/d), and resistant (7.40 + 1.54 mg/d; Tukey test, P < .001). Age had a significant inverse correlation with warfarin dose (P < .001; effective dose diminished 0.56 mg/d/decade). Required doses were higher for individuals with CYP2C9 variants containing the allele *1 compared to those individuals with variants composed of other alleles (P ¼ .006). Similarly, individuals with VKORC1-1639GG and VKORC1-1639GA genotypes also required higher doses compared to the AA genotype (P < .001). Evaluation of potential gene-gene interactions between CYP2C9 and VKORC1 polymorphisms showed significant differences in dosing for CYP2C9 genotypes within the VKORC1-1639G/A subgroup (P ¼ .013). A stepwise multivariate linear regression analysis showed that 38.2% of the warfarin dose response variance was accounted for by a model involving age (20.9%), VKORC1-1639G/A (11.3%), and CYP2C9*1, *2, and *3 variants (7.1%). These results corroborate previous findings on warfarin pharmacogenetics and define a contrastable gene-bioenvironment interaction model suited to be used in Hispanic populations.

Research paper thumbnail of Potential cognitive endophenotypes in multigenerational families: segregating ADHD from a genetic isolate

Adhd Attention Deficit and Hyperactivity Disorders

Endophenotypes are neurobiological markers cosegregating and associated with illness. These bioma... more Endophenotypes are neurobiological markers cosegregating and associated with illness. These biomarkers represent a promising strategy to dissect ADHD biological causes. This study was aimed at contrasting the genetics of neuropsychological tasks for intelligence, attention, memory, visual-motor skills, and executive function in children from multigenerational and extended pedigrees that cluster ADHD in a genetic isolate. In a sample of 288 children and adolescents, 194 (67.4%) ADHD affected and 94 (32.6%) unaffected, a battery of neuropsychological tests was utilized to assess the association between genetic transmission and the ADHD phenotype. We found significant differences between affected and unaffected children in the WISC block design, PIQ and FSIQ, continuous vigilance, and visual-motor skills, and these variables exhibited a significant heritability. Given the association between these neuropsychological variables and ADHD, and also the high genetic component underlying their transmission in the studied pedigrees, we suggest that these variables be considered as potential cognitive endophenotypes suitable as quantitative trait loci (QTLs) in future studies of linkage and association.