PubMed Health⌕ Search

Biomedical subjects

M Suthanthiran

Publications and source records attributed to M Suthanthiran.

At least 19 recordsLinked to original sources
PubMed2003

Selective loss of c-Rel compromises dendritic cell activation of T lymphocytes.

Dendritic cells initiate the immune response by presenting antigen in the context of varying levels of costimulation. The maturation state of the dendritic cell determines the quantity and quality (Th1, Th2) of the subsequent T cell response. Members of the NF-kappaB family of transcription factors have previously been implicated in dendritic cell development. Here, we used a mouse with a homozygous c-Rel deletion to investigate the role of c-Rel in the function of bone marrow derived dendritic cells. When direct presentation was evaluated, we found c-Rel(-/-) dendritic cells induce less allogeneic T cell stimulation than c-Rel(+/+) dendritic cells. In addition, T cell encounters with c-Rel(-/-) dendritic cells generate less IFN-gamma and IL-4 when compared to those with c-Rel(+/+) DCs. A similar degree of functional compromise was observed in antigen-specific T cells that were stimulated by c-Rel(-/-) dendritic cells. Functional deficits were not linked to differences in the ability to undergo maturation per se, as LPS exposure induced similar morphologic and cell surface changes in both c-Rel(+/+) and cRel(-/-) DCs. Although LPS induced a compensatory increase in the nuclear activity of fellow NF-kappaB family members, RelB and p65, LPS exposure was unable to negate the deficiencies in autologous T cell proliferation and cytokine production associated with the loss of c-Rel in dendritic cells. Taken together, our study supports a unique and non-redundant role for c-Rel in dendritic cell costimulatory capacity.

Animals↗
PubMed2003

Optimization of RNA yield, purity and mRNA copy number by treatment of urine cell pellets with RNAlater.

BACKGROUND: We have shown that measurement of mRNA for cytotoxic attack proteins perforin and granzyme B in urinary cells is a noninvasive means of diagnosing acute rejection of human renal allografts. Urinary cell mRNA studies have yielded useful information in other patient populations such as patients with cancer. The isolation of sufficient and high quality ribonucleic acid (RNA) from urinary cells however is problematic. RNAlater, an RNA stabilization solution, has been reported to optimize RNA isolation from tumor tissues stored at room temperature and from pigment-rich ocular tissues. METHODS: We explored whether the addition of RNAlater to urine cell pellets improves RNA yield, enhances purity and facilitates measurement of low abundance mRNAs. We measured, with the use of real-time quantitative polymerase chain reaction (PCR) assay, levels of expression of a constitutively expressed gene 18S rRNA and mRNA for granzyme B and transforming growth factor-beta(1) (TGF-beta(1)) in urine specimens and renal biopsies obtained from renal allograft recipients. RESULTS: RNA yield (P<0.01, Wilcoxon signed rank test) and the A260/A280 ratio (P<0.01) were both higher with urine cell pellets treated with RNAlater prior to snap freezing compared to cell pellets that were not treated with RNAlater prior to snap freezing. Levels (copy number per 1 microg of total RNA) of 18S rRNA (P<0.02), granzyme B mRNA (P=0.002) and TGF-beta(1) (P=0.02) were all higher with treated urine cell pellets compared to untreated cell pellets. Kruskall-Wallis one way analysis of variance and pair-wise comparisons with Student-Newman-Keuls test showed that the levels of mRNA for granzyme B (P<0.05) and TGF-beta(1) (P<0.05) are significantly different between renal allograft biopsies and untreated urine cell pellets but not between the biopsy specimens and RNAlater-treated urine cell pellets. CONCLUSIONS: The addition of RNAlater to urine cell pellets improves RNA isolation from urinary cells and facilitates measurement of low abundance mRNAs.

Adolescent↗
PubMed2001

Noninvasive diagnosis of renal-allograft rejection by measurement of messenger RNA for perforin and granzyme B in urine.

BACKGROUND: Acute rejection is a serious and frequent complication of renal transplantation, and its diagnosis is contingent on the invasive procedure of allograft biopsy. A noninvasive diagnostic test for rejection could improve the outcome of transplantation. METHODS: We obtained 24 urine specimens from 22 renal-allograft recipients with a biopsy-confirmed episode of acute rejection and 127 samples from 63 recipients without evidence of acute rejection. RNA was isolated from the urinary cells. Messenger RNA (mRNA) encoding the cytotoxic proteins perforin and granzyme B and a constitutively expressed cyclophilin B gene were measured with the use of a competitive, quantitative polymerase chain reaction, and the level of expression was correlated with allograft status. RESULTS: The log-transformed mean (+/-SE) levels of perforin mRNA and granzyme B mRNA, which encode cytotoxic proteins, but not the levels of constitutively expressed cyclophiiin B mRNA, were higher in the urinary cells from the 22 patients with a biopsy-confirmed episode of acute rejection than in the 63 recipients without an episode of acute rejection (perforin, 1.4+/-0.3 vs. -0.6+/-0.2 fg per microgram of total RNA; P<0.001; and granzyme B, 1.2+/-0.3 vs. -0.9+/-0.2 fg per microgram of total RNA; P<0.001). Analysis involving the receiver-operating-characteristic curve demonstrated that acute rejection can be predicted with a sensitivity of 83 percent and a specificity of 83 percent with the use of a cutoff value of 0.9 fg of perforin mRNA per microgram of total RNA, and with a sensitivity of 79 percent and a specificity of 77 percent with the use of a cutoff value of 0.4 fg of granzyme B mRNA per microgram of total RNA. Sequential urine samples were obtained from 37 patients during the first nine days after transplantation; and measurements of the levels of mRNA that encoded cytotoxic proteins identified those in whom acute rejection developed. CONCLUSIONS: Measurement of mRNA encoding cytotoxic proteins in urinary cells offers a noninvasive means of diagnosing acute rejection of renal allografts.

Acute Disease↗
PubMed2000

Transforming growth factor-beta 1 hyperexpression in African-American hypertensives: A novel mediator of hypertension and/or target organ damage.

Hypertension, a remediable risk factor for stroke, cardiovascular disease, and renal failure, affects 50 million individuals in the United States alone. African Americans (blacks) have a higher incidence and prevalence of hypertension and hypertension-associated target organ damage compared with Caucasian Americans (whites). Herein, we explored the hypotheses that transforming growth factor-beta(1) (TGF-beta(1)) is hyperexpressed in hypertensives compared with normotensives and that TGF-beta(1) overexpression is more frequent in blacks compared with whites. These hypotheses were stimulated by our recent demonstration that TGF-beta(1) is hyperexpressed in blacks with end-stage renal disease compared with white end-stage renal disease patients and by the biological attributes of TGF-beta(1), which include induction of endothelin-1 expression, stimulation of renin release, and promotion of vascular and renal disease when TGF-beta(1) is produced in excess. TGF-beta(1) profiles were determined in black and white hypertensive subjects and normotensive controls and included circulating protein concentrations, mRNA steady-state levels, and codon 10 genotype. Our investigation demonstrated that TGF-beta(1) protein levels are highest in black hypertensives, and TGF-beta(1) protein as well as TGF-beta(1) mRNA levels are higher in hypertensives compared with normotensives. The proline allele at codon 10 (Pro(10)) was more frequent in blacks compared with whites, and its presence was associated with higher levels of TGF-beta(1) mRNA and protein. Our findings support the idea that TGF-beta(1) hyperexpression is a risk factor for hypertension and hypertensive complications and provides a mechanism for the excess burden of hypertension in blacks.

Black or African American↗
PubMed2000

Dendritic cells armed with anti-CD3 mAbs reduce pulmonary metastases, prolong survival, and engender antitumor effector cells demonstrable by adoptive transfer.

BACKGROUND: Dendritic cells (DCs) pulsed with tumor cells or peptides are effective antitumor agents in a number of tumor models. In light of our earlier demonstration that T-cell signaling via the CD3 proteins induces cytolytic activity and constrains tumor progression, we equipped DCs pulsed with tumor cells with anti-CD3 mAbs and tested their antitumor efficacy in a murine renal cell cancer pulmonary metastasis model. METHODS: We investigated the antitumor efficacy of DCs pulsed with whole irradiated tumor cells (DC/R) or DCs pulsed with irradiated tumor cells and armed with anti-CD3 mAbs (DC/R/anti-CD3 mAbs). Experimental end points included the number of pulmonary metastases and survival of tumor-inoculated mice. RESULTS: Our studies demonstrate that arming tumor-pulsed DCs with anti-CD3 mAbs results in a superior outcome compared to that from tumor-pulsed DCs alone in terms of reduction in the number of pulmonary metastases and survival times. Furthermore, adoptive transfer experiments revealed that the splenocytes from DC/R/anti-CD3 mAbs-treated mice are superior to splenocytes from DC/R-treated mice in reducing renal cancer pulmonary metastases in severe combined immunodeficient (SCID) beige mice. CONCLUSION: Our data suggest that the therapeutic efficacy of DCs pulsed with tumor cells can be augmented by arming them with anti-CD3 mAbs. DC-based treatment regimens that currently are being pursued in clinical trials might be improved by equipping such cells with anti-CD3 mAbs.

Adoptive Transfer↗
PubMed2000

Hypertension-induced organ damage in African Americans: transforming growth factor-beta(1) excess as a mechanism for increased prevalence.

Hypertension is prevalent world-wide, and it affects over 50 million individuals in the United States alone. African Americans (blacks) have a high prevalence of hypertension, develop it at an earlier age, and suffer excessively from severe or malignant hypertension. They also have a high prevalence of target organ damage attributable to hypertension, including left ventricular hypertrophy, stroke, end-stage renal disease (ESRD) and coronary artery disease. Hypertensive nephrosclerosis is particularly more prevalent in blacks compared to whites, and there is evidence that factors in addition to elevated blood pressure contribute to its pathogenesis. Transforming growth factor-beta 1 (TGF-beta1) is a fibrogenic cytokine that has been implicated in the development and progression of experimental and human renal diseases. We have demonstrated that blacks with ESRD have higher circulating levels of TGF-beta1 protein compared to whites with ESRD. We have also found that hyperexpression of TGF-beta1 is more frequent in blacks with hypertension than in whites. We propose that TGF-beta1 hyperexpression may be an important mediator of hypertension and hypertensive nephrosclerosis. We hypothesize also that the increased frequency of TGF-beta1 hyperexpression may contribute to the excess burden of ESRD in blacks. Based on our hypotheses, and the observations that angiotensin-converting enzyme inhibitors and angiotensin receptor antagonists reduce angiotensin II-mediated stimulation of TGF-beta1 production, we propose that treatment with these agents might be efficacious in preventing or slowing the progression of target organ damage in hypertensive blacks.

Angiotensin II↗
PubMed2000

The importance of genetic polymorphisms in renal transplantation.

Genetic variations including single nucleotide polymorphisms, dinucleotide repeats and microsatellites have been identified in a number of genes encoding cytokines, cytokine receptors, chemokines and their receptors, adhesion molecules. Several of the polymorphisms are located in the promoter region of the gene, affect transcription or translation, and not infrequently determine the level of expression of the protein product. An interesting and testable hypothesis for the clinical heterogeneity and differential responsiveness in allograft recipients is genetic variation. These nucleotide sequence variations, polymorphisms located in genes contributing to immune repertory and in genes responsible for drug metabolism, are excellent candidates for the differential clinical phenotype.

Cytokines↗
PubMed2000

Prospects and applicability of molecular diagnosis of allograft rejection.

We believe that changes in blood urea nitrogen and plasma creatinine are, at best, surrogate markers for rejection. It seems certain that rejection, an immunologic process must precede deterioration in renal function. We suggest that the efforts to prevent chronic rejection should include an effective means to diagnose rejection before the advent of fixed renal injury. Through an analysis of transcription for a series of genes that are expressed by activated, but not resting, cytotoxic lymphocytes, eg, granzyme B, a remarkably accurate tool for assessing the presence of rejection has emerged. Although our methods first centered on analysis of kidney transplant biopsy specimens, noninvasive surveillance using transcriptional profiling analysis circulating blood or urine sediment cells has proven equally informative.

Animals↗
PubMed1999

Cyclosporine induces cancer progression by a cell-autonomous mechanism.

Malignancy is a common and dreaded complication following organ transplantation. The high incidence of neoplasm and its aggressive progression, which are associated with immunosuppressive therapy, are thought to be due to the resulting impairment of the organ recipient's immune-surveillance system. Here we report a mechanism for the heightened malignancy that is independent of host immunity. We show that cyclosporine (cyclosporin A), an immunosuppressant that has had a major impact on improving patient outcome following organ transplantation, induces phenotypic changes, including invasiveness of non-transformed cells, by a cell-autonomous mechanism. Our studies show that cyclosporine treatment of adenocarcinoma cells results in striking morphological alterations, including membrane ruffling and numerous pseudopodial protrusions, increased cell motility, and anchorage-independent (invasive) growth. These changes are prevented by treatment with monoclonal antibodies directed at transforming growth factor-beta (TGF-beta). In vivo, cyclosporine enhances tumour growth in immunodeficient SCID-beige mice; anti-TGF-beta monoclonal antibodies but not control antibodies prevent the cyclosporine-induced increase in the number of metastases. Our findings suggest that immunosuppressants like cyclosporine can promote cancer progression by a direct cellular effect that is independent of its effect on the host's immune cells, and that cyclosporine-induced TGF-beta production is involved in this.

Animals↗
PubMed1999

Lymphocyte intracellular free calcium concentration is increased in preeclampsia.

OBJECTIVES: We tested 2 hypotheses: (1) Preeclampsia is characterized by an increase in intracellular free calcium concentration in lymphocytes. (2) Levels of intracellular free calcium are influenced by the calcium concentration in the extracellular milieu or by parathyroid hormone. STUDY DESIGN: Intracellular free calcium concentrations were measured in 4 groups of women: nonpregnant women (n = 25), normotensive pregnant women (n = 30), pregnant women with chronic hypertension (n = 15), and women with preeclampsia (n = 15). Intracellular free calcium concentration was measured in the basal state, at varying extracellular calcium ion concentrations, and in the presence of exogenous parathyroid hormone. RESULTS: Women with preeclampsia had the highest basal lymphocyte intracellular free calcium concentration (121 +/- 7 nmol/L, mean +/- SEM) compared with normotensive pregnant women during the third trimester (94 +/- 3 nmol/L, P <.001) and pregnant women in the third trimester with chronic hypertension (100 +/- 3 nmol/L, P <.01). During the third trimester normotensive women and women with chronic hypertension had significantly higher basal intracellular free calcium concentrations than were found in women during the first trimester. Exposure of lymphocytes to an extracellular milieu of low calcium concentration resulted in an increase in intracellular free calcium concentration. Incubation with parathyroid hormone had no effect on intracellular free calcium concentration. CONCLUSIONS: Lymphocyte intracellular free calcium concentration is increased in preeclampsia and not in chronic hypertensive pregnancy and is greater during the third trimester than during the first trimester. Extracellular calcium depletion increases lymphocyte intracellular free calcium concentration. These data support the idea that a calcium deficit leading to an increased intracellular free calcium concentration during late pregnancy contributes to the pathogenesis of preeclampsia.

Calcium↗
PubMed1999

TGF-beta1 DNA polymorphisms, protein levels, and blood pressure.

Transforming growth factor-beta1 (TGF-beta1), a multifunctional cytokine with fibrogenic properties, has been implicated in the pathogenesis of the vascular and target organ complications of hypertension. TGF-beta1 may also regulate blood pressure via stimulation of endothelin-1 and/or renin secretion. Herein we explored the hypothesis that circulating levels of TGF-beta1 protein (quantified using a TGF-beta1-specific sandwich ELISA) are correlates of blood pressure levels. This hypothesis was tested in 98 stable end-stage renal disease (ESRD) patients. (The use of ESRD patients as the study cohort eliminates renal function-dependent alterations in circulating levels of TGF-beta1 protein.) In addition, in view of the previously reported correlation among TGF-beta1 DNA polymorphisms and systolic blood pressure, TGF-beta1 codon 25 genotype and alleles were identified in 71 hypertensive subjects and 57 normotensives using amplification refractory mutation system polymerase chain reaction. Our studies demonstrate for the first time that TGF-beta1 levels (209+/-13 ng/mL, mean+/-SEM) are positive correlates (Pearson correlation analysis) of mean arterial pressure (P=0.008), systolic pressure (P=0.02), and diastolic pressure (P=0. 01). We also report that a higher percentage of hypertensives (92%) compared with normotensives (86%) are homozygous for the arginine allele at codon 25. Our observations support the idea that genetically determined TGF-beta1 protein concentrations may play a role in blood pressure regulation in humans.

Amino Acid Substitution↗
PubMed1998

In vivo expression of transforming growth factor-beta1 in humans: stimulation by cyclosporine.

BACKGROUND: Transforming growth factor-beta1 (TGF-beta1) is an immunoregulatory and fibrogenic cytokine. In an earlier in vitro study, we demonstrated that cyclosporine (CsA) increases TGF-beta1 transcription rate in human T lymphocytes. Herein, we explored whether CsA augments the in vivo expression of TGF-beta1 in humans. METHODS: The inherent difficulty in studying the in vivo effect of CsA in humans was circumvented by investigating stable end-stage renal disease patients who were preconditioned with CsA before their living donor renal transplantation. Sera and peripheral blood mononuclear cells were obtained from CsA-preconditioned patients and quantified for TGF-beta1 expression at the mRNA (by competitive polymerase chain reaction) and protein (sandwich enzyme-linked immunosorbent assay) levels. RESULTS: Our studies demonstrated a significant increase in TGF-beta1 expression after CsA therapy. The stimulatory effect was unique to TGF-beta1, and CsA did not increase interleukin (IL)-10, IL-6, IL-2, or tumor necrosis factor-alpha expression. CONCLUSIONS: Our first-time demonstration of a TGF-beta1-selective in vivo stimulatory effect of CsA in humans: (1) advances a TGF-beta1-centered hypothesis for the beneficial (immunosuppression) and detrimental (fibrosis, hypertension) effects of CsA use, and (2) broadens the mechanism of immunosuppressive action of CsA to include heightened expression of an endogenous immunosuppressive cytokine.

Cyclosporine↗
PubMed1998

Mechanisms and management of acute renal allograft rejection.

We used RT-PCR for the molecular characterization of human renal graft rejection. The studies showed that intragraft display of mRNA encoding cytotoxic attack molecule granzyme B, and immunoregulatory cytokines IL-10 or IL-2 are correlates of acute rejection, and intrarenal expression of TGF-1 mRNA, of chronic rejection. The current immunosuppressive protocol involves the use of multiple drugs, each directed at a discrete site in the T-cell activation cascade and each with distinct side effects. The immunosuppressants can be classified as inhibitors of: transcription (CsA, tacrolimus); nucleotide synthesis (azathioprine, mycophenolate mofetil, and mizoribine); growth factor signal transduction (sirolimus); and differentiation (DSG). Polyclonal antibodies and monoclonal antibodies directed at cell surface proteins are quite effective as induction therapy or anti-rejection drugs.

Acute Disease↗