Biomedical subjects

Rakesh K Singh

Publications and source records attributed to Rakesh K Singh.

At least 19 recordsLinked to original sources

PubMed2006

CCL21-induced immune cell infiltration.

Cellular immune responses can be initiated via peptide presentation by specialized antigen presenting cells, dendritic cells (DCs), which stimulate naïve T cells. The trafficking of DCs and T cells is regulated by chemokines such as CCL21. CCL21 is normally expressed in the lymphoid organs and coordinates the interactions between DCs and T cells, thereby contributing to the initiation of T cell responses. In order to comprehend the mechanisms of CCL21 activity and to utilize CCL21 optimally in therapy, understanding the kinetics of the responses of various cell types to CCL21 would be beneficial. Therefore, in this study, we injected mice subcutaneously (s.c.) with CCL21 and examined the DC and T cell infiltration of the local draining lymph node. CCL21 injection resulted in significantly increased numbers of lymphoid and myeloid DCs and effector T lymphocytes in the local node at 4 days. Furthermore, at 4 days small lymphoid-like structures were visible in the injection areas. These results provide guidance for the optimal timing of CCL21 use in combination with vaccines.

Animals↗

PubMed2006

Supercritical fluid extraction of limonoid glucosides from grapefruit molasses.

Limonoid glucosides (primarily limonin 17-beta-D-glucopyranoside, LG) were extracted from grapefruit molasses by supercritical fluid extraction using a supercritical carbon dioxide-ethanol (SC CO(2)-ethanol) system. Extraction conditions to maximize the yield of LG were determined by varying pressure, temperature, ethanol concentration, and extraction time. The highest yield of LG at 0.61 mg/g molasses was obtained at a pressure 48.3 MPa, a temperature of 50 degrees C, 10% ethanol (X(Eth) = 0.1), and 40 min of extraction time at a flow rate of 5.0 L/min. The results demonstrated that SC CO(2) extraction of limonoid glucosides from grapefruit molasses has practical significance for commercial production.

Chromatography, Supercritical Fluid↗

PubMed2006

Rapid, noninvasive diagnosis of visceral leishmaniasis in India: comparison of two immunochromatographic strip tests for detection of anti-K39 antibody.

Used with blood or serum, a new anti-K39 antibody immunochromatographic strip test (IT-Leish; DiaMed AG) proved sensitive (range, 99 to 100%) and specific (range, 95 to 100%) for the noninvasive serodiagnosis of visceral leishmaniasis in India. Used with serum, the IT-Leish test and the existing Kalazar Detect test (InBios International, Inc.) yielded comparable results for symptomatic infection and identified apparent subclinical infection in 15 to 32% of healthy residents in a region where visceral leishmaniasis is highly endemic.

Animals↗

PubMed2006

Distinct expression of CXCL8 and its receptors CXCR1 and CXCR2 and their association with vessel density and aggressiveness in malignant melanoma.

We examined the expression of CXCL8 (interleukin-8), its receptors, CXCR1 and CXCR2, and vessel density in human melanoma by immunohistochemical analysis of tumors from different Clark levels, depths, and thicknesses. Expression of CXCL8 and CXCR2 was lower in Clark level I and II specimens than in level III through V specimens and metastases. CXCR1 expression was observed ubiquitously in the majority of human melanoma tumor specimens irrespective of disease state, with the highest intensity in Clark level III specimens. We observed a significant difference in CXCL8 and CXCR2 expression between thin ( 0.75 mm) melanomas and between thin and metastatic lesions. Positive correlations were observed between Clark level and CXCL8 or CXCR2 and between thickness and CXCR2 expression. We found no correlation between vessel density and Clark level or thickness. Our data suggest that expression of CXCL8 and CXCR2 contributes to aggressive growth and metastasis in human malignant melanoma. Consistent with the transition from radial to vertical growth phase melanoma, expression of CXCL8 and its receptor, CXCR2, may be key in the switch to an aggressive, more metastatic phenotype.

Disease Progression↗

PubMed2006

Severe childhood autosomal recessive muscular dystrophy, mental subnormality and chorea.

Severe childhood autosomal recessive muscular dystrophy (SCARMD) is characterized by a severe Duchene muscular dystrophy like phenotype. Most such cases represent alpha or gamma sarcoglycanopathies. Mental subnormality is very uncommon and other central nervous system deficits have not been documented in patients with SCARMD. We report a brother and sister with the SCARMD phenotype, who additionally had static mental subnormality and choreiform movements. Work-up for sarcolgycan genes, dystrophin gene and known causes of mental retardation and chorea was normal.

Child↗

PubMed2005

Down-regulation of vascular endothelial cell growth factor-C expression using small interfering RNA vectors in mammary tumors inhibits tumor lymphangiogenesis and spontaneous metastasis and enhances survival.

Tumor production of vascular endothelial cell growth factor (VEGF)-C is associated with tumor lymphangiogenesis and lymph node metastasis. In this study, we examined the effects of small interfering RNA (siRNA)-mediated inhibition of VEGF-C on murine mammary tumor growth, metastasis, and survival. The mRNA and protein expression of VEGF-C in murine mammary tumor cells stably transfected with a VEGF-C siRNA vector were significantly lower compared with VEGF-C-control vector-transfected cells. Cl66-siVEGFC tumors had lower levels of lymphangiogenesis and lymph node and spontaneous lung metastasis than Cl66-control tumors. However, we did not observe significant differences in primary tumor growth and experimental lung metastasis between mice injected with Cl66-siVEGFC and Cl66-control cells. In addition, mice bearing Cl66-siVEGFC tumors lived significantly longer than mice bearing Cl66-control tumors. Furthermore, our data suggest that inhibition of VEGF-C modulates immune cell infiltration and their function, which might be critical in tumor immunity. In summary, our data show that inhibition of VEGF-C expression using siRNA-mediated gene silencing vectors reduces lymphangiogenesis and lymph node and spontaneous lung metastasis, and enhances survival.

Animals↗

PubMed2005

Repeat infective endocarditis: differentiating relapse from reinfection.

Repeat infective endocarditis due to the same species can represent relapse of the initial infection or a new infection. We used time-based clinical criteria and pulsed-field gel electrophoresis-based molecular criteria to classify 13 cases of repeat infective endocarditis as either relapse or reinfection. The agreement between clinical and molecular criteria was imperfect (agreement in 10 [77%] of 13 cases).

Endocarditis, Bacterial↗

PubMed2005

Autocrine role of interleukin-8 in induction of endothelial cell proliferation, survival, migration and MMP-2 production and angiogenesis.

Interleukin-8 (IL-8/CXCL8), a paracrine angiogenic factor, modulates multiple biologic functions in CXCR1 and CXCR2 expressing endothelial cells. Several reports suggest that inflammation, infection, cellular stress and tumor presence regulate IL-8 production in endothelial cells. In the present study, we test the hypothesis that IL-8 regulates multiple biological effects in endothelial cells in an autocrine manner. We examined the autocrine role of IL-8 in regulating angiogenesis by using a neutralizing antibody to IL-8, CXCR1 or CXCR2 in human vein umbilical endothelial cell (HUVEC) and human dermal microvascular endothelial cell (HMEC). Neutralizing antibody to IL-8, CXCR1 or CXCR2 inhibited endothelial cell proliferation, and MMP-2 production as compared to cells cultured with medium alone or control antibody. In addition, we observed that the number of apoptotic cells was significantly higher in anti-IL-8, anti-CXCR1 and anti-CXCR2 treated endothelial cells, which coincided with decreased survival-associated gene expression. We observed reduced migration of endothelial cells treated with anti-IL-8 and anti-CXCR2 antibody, but not anti-CXCR1 antibody as compared to controls. Further, we observed an inhibition of capillary tube formation and neovascularization following treatment with anti-IL-8, anti-CXCR1 and anti-CXCR2 antibodies. Together these data suggest that IL-8 functions as an important autocrine growth and angiogenic factor in regulating multiple biological activities in endothelial cells.

Autocrine Communication↗

PubMed2005

MMP-7 promotes prostate cancer-induced osteolysis via the solubilization of RANKL.

We developed a rodent model that mimics the osteoblastic and osteolytic changes associated with human metastatic prostate cancer. Microarray analysis identified MMP-7, cathepsin-K, and apolipoprotein D as being upregulated at the tumor-bone interface. MMP-7, which was produced by osteoclasts at the tumor-bone interface, was capable of processing RANKL to a soluble form that promoted osteoclast activation. MMP-7-deficient mice demonstrated reduced prostate tumor-induced osteolysis and RANKL processing. This study suggests that inhibition of MMP-7 will have therapeutic benefit in the treatment of prostate cancer-induced osteolysis.

Acid Phosphatase↗

PubMed2005

Murine mammary adenocarcinoma cells transfected with p53 and/or Flt3L induce antitumor immune responses.

Transfection of tumors with tumor-associated antigens (Ags) or cytokines can increase immunogenicity and slow down tumor growth. However, the effect of cotransfection with genes that encode a tumor-associated Ag, such as the tumor suppressor gene p53, and a cytokine has been rarely investigated. We report that transfection of 4T1 mammary tumor cells (p53-null) with the dendritic cell (DC) growth factor, fms-like tyrosine kinase 3 ligand (Flt3L), significantly delayed their growth in vivo, resulting in the rejection of 100% of the tumors formed by injection of tumor cells cotransfected with Flt3L and p53. Immunization with irradiated 4T1 cells transfected with Flt3L induced DC infiltration of the immunization site and significantly increased the antitumor T-cell responses. Further, immunization with irradiated 4T1 cells cotransfected with p53 and Flt3L significantly increased p53-specific immune responses, as compared to vaccination with 4T1 cells transfected with either Flt3L or p53 alone. These responses included increased activity against clone 66 (Cl-66), a sister tumor to 4T1 with high murine mutant p53 expression levels. Challenge with Cl-66 revealed that immunization with irradiated 4T1-Flt3L-p53 cells significantly slowed growth, prolonged survival, and resulted in complete remissions. Further, immunization with irradiated 4T1-Flt3L also slowed Cl-66 growth, although to a lesser extent than 4T1-Flt3L-p53. We suggest that immunization with DCs transfected with the Flt3L transgene and a tumor Ag may potentially heighten T-cell responses and therapeutic activity.

Adenocarcinoma↗

PubMed2005

Paracrine regulation of vascular endothelial growth factor--a expression during macrophage-melanoma cell interaction: role of monocyte chemotactic protein-1 and macrophage colony-stimulating factor.

Tumor-associated macrophages are major infiltrates of human solid malignancies and play an important role in tumor angiogenesis by production of angiogenic factors. In the present study, we examined whether macrophage- melanoma cell interaction regulates vascular endothelial cell growth factor-A (VEGF-A) expression in macrophages. We analyzed the expression of mediators of monocyte recruitment and differentiation, such as monocyte chemotactic protein-1 (MCP-1) and macrophage colony-stimulating factor (M-CSF) in malignant melanoma specimens and tumor cells with different metastatic potential. Our data demonstrate that MCP-1 and M-CSF are differentially expressed in human malignant melanomas from different thickness and depth of invasion and cell lines. Next, we examined the effect of MCP-1 and M-CSF on modulation of VEGFA expression in monocytes/macrophages. Treatment of human monocytes with M-CSF and MCP-1 enhanced VEGF-A expression by increased hypoxia-inducible factor-1alpha (HIF-1alpha) expression and enhanced activation of the hypoxia response element (HRE). Further activation of monocytes and monocyte-derived macrophages (MDM) by lipopolysaccharide (LPS) caused an increase in VEGF-A expression. We demonstrate that coculture of melanoma cells with monocytes enhanced VEGF-A secretion, and conditioned medium from MDMs enhanced melanoma cell expression of VEGF-A. Furthermore, conditioned medium from melanoma cells enhanced VEGF-A expression in human monocytes, which was abrogated by anti-M-CSF neutralizing antibody. In summary, we demonstrate that MCP-1 and M-CSF, critical for monocyte recruitment, activation, and differentiation, differentially regulate VEGF-A expression and may play an important role in monocyte/macrophage- mediated tumor angiogenesis.

Blotting, Western↗

PubMed2005

Tumour-associated macrophage infiltration, neovascularization and aggressiveness in malignant melanoma: role of monocyte chemotactic protein-1 and vascular endothelial growth factor-A.

The objective of this study was to evaluate the role of tumour-associated macrophages (TAMs) in malignant melanoma progression, invasion and angiogenesis. We examined the levels of macrophage infiltration and monocyte chemotactic protein-1 (MCP-1), neovascularization and vascular endothelial growth factor-A (VEGF-A) in different Clark's level melanomas with varying thicknesses and metastases. The level of TAM density was significantly higher in thick (>0.75 mm) than thin ( 0.75 mm) than thin (<or=0.75 mm) melanomas and negatively correlated with melanoma aggressiveness and invasion. We did not observe any significant difference in the levels of neovascularization between thin and thick melanomas, and no correlation with VEGF-A expression, TAM density or melanoma aggressiveness and invasion. Interestingly, levels of VEGF-A were significantly higher in metastatic melanoma than in thick melanoma. In addition, we observed lower levels of MCP-1 messenger RNA (mRNA) expression in more aggressive melanomas and in cell lines with higher metastatic potential. In summary, our data suggest a distinct pattern of TAM infiltration, MCP-1 expression, neovascularization and VEGF-A expression during human melanoma progression, and a complex interaction between TAMs and melanoma cells in the regulation of melanoma progression, angiogenesis and metastasis.

Cell Line, Tumor↗

PubMed2004

Constitutive expression of growth regulated oncogene (gro) in human colon carcinoma cells with different metastatic potential and its role in regulating their metastatic phenotype.

The purpose of this study was to examine the expression and functional significance of the growth-regulated oncogene (gro) family in human colon carcinoma growth and metastasis. We examined constitutive expression of CXCL1 (gro-alpha), CXCL2 (gro-beta), CXCL3 (gro-gamma) and their receptor, CXCR2 in human colon carcinoma cells with different metastatic potentials. Non-metastatic and low metastatic cells expressed lower levels of CXCL1 and CXCR2 mRNA and protein as compared to high metastatic colon carcinoma cells. No difference in CXCL2 and CXCL3 mRNA expression levels was observed. Colon carcinoma cells expressing higher levels of CXCL1 exhibit increased proliferation and invasive potential. Furthermore, exogenous addition of recombinant human CXCL1 significantly enhanced the proliferation and invasiveness of colon carcinoma cells. Furthermore, treatment of KM12C cells with exogenous CXCL1 enhanced their invasiveness. Neutralizing antibody to CXCL1 in combination with antibody to CXCR2 inhibited highly metastatic KM12L4 (high CXCL1 expressor) cell proliferation. These data demonstrate that the constitutive expression of CXCL1 and its receptor CXCR2 is associated with metastatic potential and modulates colon cancer cell proliferation and an invasive phenotype.

Animals↗

PubMed2003

IL-8 directly enhanced endothelial cell survival, proliferation, and matrix metalloproteinases production and regulated angiogenesis.

IL-8, a member of the chemokine family, has been shown to play an important role in tumor growth, angiogenesis, and metastasis. The objective of this study was to determine the mechanism of IL-8-mediated angiogenesis. We examined the direct role of IL-8 in angiogenesis by examining IL-8 receptor expression on endothelial cells and their proliferation, survival, and matrix metalloproteinases (MMPs) production. We demonstrate that HUVEC and human dermal microvascular endothelial cells constitutively express CXCR1 and CXCR2 mRNA and protein. Recombinant human IL-8 induced endothelial cell proliferation and capillary tube organization while neutralization of IL-8 by anti-IL-8 Ab blocks IL-8-mediated capillary tube organization. Incubation of endothelial cells with IL-8 inhibited endothelial cell apoptosis and enhanced antiapoptotic gene expression. Endothelial cells incubated with IL-8 had higher levels of Bcl-x(L):Bcl-x(S) and Bcl-2:Bax ratios. Furthermore, incubation of endothelial cells with IL-8 up-regulated MMP-2 and MMP-9 production and mRNA expression. Our data suggest that IL-8 directly enhanced endothelial cell proliferation, survival, and MMP expression in CXCR1- and CXCR2-expressing endothelial cells and regulated angiogenesis.

Apoptosis↗

PubMed2003

Expression of CXCR1 and CXCR2 receptors in malignant melanoma with different metastatic potential and their role in interleukin-8 (CXCL-8)-mediated modulation of metastatic phenotype.

In the present study, we examined the autocrine/paracrine role of IL-8 in melanoma growth and metastasis by analyzing the expression and functional significance of IL-8 receptors, CXCR1 and CXCR2 in human malignant melanoma cells with different metastatic potential. CXCR1 and CXCR2 mRNA and protein levels were analyzed by reverse trannscriptase-based polymerase chain reaction, immunohistochemistry, immunoprecipitation, flow cytometry and ligand binding assay in melanoma cells in vitro and xenografted in nude mice. Melanoma cells constitutively expressed CXCR1 and CXCR2 mRNA and protein. Highly metastatic A375SM cells expressed higher levels of CXCR1 and CXCR2 mRNA and protein in vitro and in vivo as compared to low metastatic A375P and non-metastatic SBC-2 melanoma cells. Treatment of SBC-2 and A375P cells with exogenously added recombinant IL-8 significantly enhanced their proliferation and invasive potential. Further neutralizing antibodies to CXCR1 and CXCR2 inhibited proliferation and invasive potential of unstimulated and IL-8-stimulated A375P cells. In summary, the data suggest that constitutive expression of CXCR1 and CXCR2 play an important role regulating the IL-8-mediated metastatic phenotype in human malignant melanoma cells.

Animals↗

PubMed2003

Increased expression of MMP-2, MMP-9 (type IV collagenases/gelatinases), and MT1-MMP in canine X-linked Alport syndrome (XLAS).

BACKGROUND: Alport syndrome is a group of genetic disorders resulting from mutations in either the alpha3(IV), alpha4(IV) or alpha5(IV) collagen chains. The disease is characterized by a progressive glomerulonephritis, usually associated with a high-frequency specific sensorineural hearing loss, dot and fleck retinopathy, and lens abnormalities. Dogs with naturally occurring genetic disorders of basement membrane collagen (type IV) may serve as animal models of Alport syndrome. In this study, a well-characterized naturally occurring canine model was employed to demonstrate a potential role for matrix metalloproteinases (MMPs) in Alport renal disease pathogenesis. METHODS: Adolescent male dogs that developed renal failure were euthanized and necropsied. Clinicopathologic features of the disease were characterized, and kidneys from normal and Alport dogs were analyzed by gelatin zymography, Western blotting, in situ zymography, immunohistology, and by reverse transcription polymerase chain reaction (RT-PCR) for expression of MMP-2, MMP-9, and membrane type 1-MMP (MT1-MMP). RESULTS: Affected dogs developed proteinuria and rapidly progressive juvenile-onset chronic renal failure. The activities of MMP-2 and MMP-9 were significantly induced in Alport kidney. In situ zymography confirmed elevated active metalloproteinases in kidney cryosections of affected dogs. The mRNAs encoding MMP-2, MMP-9 and MT1-MMP were also increased in Alport dogs suggesting that elevated expression of MMPs reflects events in the progression of Alport syndrome in dogs. CONCLUSION: Elevated expression of MMP-2, MMP-9, and MT1-MMP is observed in fibrotic renal cortex from X-linked Alport syndrome dogs. These findings suggest that MMPs may play an important role in matrix accumulation associated with progressive renal scarring in this model.

Animals↗

PubMed2003

Use of matrix metalloproteinase (MMP)-9 knockout mice demonstrates that MMP-9 activity is not absolutely required for G-CSF or Flt-3 ligand-induced hematopoietic progenitor cell mobilization or engraftment.

Recombinant growth factors (GFs) are used to mobilize hematopoietic stem cells (HSCs) for autologous and allogeneic transplantation; however, little is known about the mechanism(s) critical to this process. Increased levels of serum matrix metalloproteinase (MMP)-9 are detected during mobilization by G-CSF in humans or interleukin (IL)-8 in primates and mice, suggesting a role for this molecule in mobilization. Further, antibodies to MMP-9 block IL-8-induced mobilization. To investigate the role of MMP-9, we compared G-CSF and Flt-3 ligand (Flt-3L)-induced mobilization in wild-type (WT) and MMP-9 knockout (KO) mice. The absence of MMP-9 in the KO mice was confirmed by zymography, which also revealed that serum MMP-9 levels were elevated in WT mice following G-CSF administration. We report that MMP-9 KO mice did not have impaired G-CSF- or Flt-3L-induced hematopoietic progenitor mobilization, suggesting that MMP-9 is not an absolute requirement for this process. In addition, MMPs produced by HSCs have been demonstrated to be important for their transmigration; however, we demonstrate that the engraftment of MMP-9-deficient bone marrow HSCs was not impaired in sublethally irradiated WT recipients. We conclude that while MMP-9 may play an important role in GF-induced hematopoietic progenitor mobilization and engraftment in WT animals, compensatory upregulation of enzymes with a similar activity profile to MMP-9 may obscure the impact of MMP-9 deficiency in the KO model.

Animals↗

PubMed2002

Capsaicin regulates vascular endothelial cell growth factor expression by modulation of hypoxia inducing factor-1alpha in human malignant melanoma cells.

PURPOSE: Capsaicin (8-Methyl-N-Vanillyl-6-nonenamide), a known natural dietary chemopreventive agent, inhibits malignant melanoma cell proliferation. In the present study, we examined the effect of capsaicin on constitutive and induced vascular endothelial cell growth factor (VEGF) expression in malignant melanoma cells. RESULTS: Capsaicin treatment resulted in enhanced VEGF protein secretion in malignant melanoma cells independent of IL-1beta and TNF-alpha. The observed up-regulation of VEGF production by capsaicin was concentration- and duration-dependent and was inversely associated with inhibition of melanoma cell proliferation. We observed an increase in hypoxia-inducible factor (HIF)-1alpha and VEGF mRNA expression in capsaicin-treated melanoma cells. Further, an electrophoretic mobility shift assay (EMSA) from nuclear extracts from melanoma cells showed a decrease in constitutive activation of NF-kappaB and enhanced HIF-1alpha binding activity to hypoxia response element (HRE) in melanoma cells treated with different concentrations of capsaicin. CONCLUSIONS: These data suggest that inhibition of cellular proliferation by capsaicin follows enhanced VEGF production by remaining melanoma cells by enhancing HIF-1alpha expression and binding to HRE.

Capsaicin↗