Biomedical subjects

Srinivasan Rajaraman

Publications and source records attributed to Srinivasan Rajaraman.

11 recordsLinked to original sources

PubMed2006

Targeted molecular therapy of the PI3K pathway: therapeutic significance of PI3K subunit targeting in colorectal carcinoma.

OBJECTIVE: The phosphatidylinositol 3-kinase (PI3K) pathway promotes cancer cell proliferation and survival. The authors determined the pattern of distribution of PI3K pathway components (ie, the p85alpha regulatory subunit, p110alpha catalytic subunit, Akt1, Akt2, and the tumor suppressor PTEN) in human colorectal cancer. In addition, inhibition of in vitro proliferation and in vivo liver metastasis by p85alpha or p110alpha siRNA treatment was analyzed. SUMMARY BACKGROUND DATA: Small interfering RNA (siRNA) molecules suppress expression of target genes and may have therapeutic applications as target-specific therapies for cancer. Therefore, the purpose of this study was 2-fold: 1) to analyze the distribution pattern of PI3K pathway components in human normal colorectal cancers, and 2) to determine whether targeted inhibition of PI3K inhibits colon cancer growth in vitro and suppresses metastatic growth in vivo. METHODS: Immunohistochemical analysis was performed on colorectal adenocarcinomas and adjacent normal mucosa for PI3K pathway components, including p85alpha, p110alpha, Akt1, Akt2, and the tumor suppressor PTEN, which inhibits PI3K. HT29 and KM20 human colon cancer cells were treated with siRNA directed to p85alpha or p110alpha, and cell viability and apoptosis assessed. HT29 cells, transfected with a plasmid containing green fluorescent protein (GFP), were injected into the spleen of athymic nude mice to establish liver metastases; mice were randomized to receive either nontargeting control (NTC), p85alpha or p110alpha siRNA. RESULTS: PI3K pathway components p85alpha and Akt2 were highly expressed in glandular elements of colon cancers, with a correlation between staining intensity and clinical stage; PTEN expression was decreased in the colon cancers of all stages. PI3K-specific siRNA treatment decreased cell viability in vitro and suppressed metastatic tumor growth in vivo. CONCLUSIONS: Selective targeting of PI3K pathway components may enhance the effects of standard chemotherapeutic agents and provide novel adjuvant treatment of selected colorectal cancers.

Adult↗

PubMed2005

Sensor fault diagnosis for nonlinear processes with parametric uncertainties.

This paper addresses the problem of detecting, discriminating, and reconstructing sensor faults for nonlinear systems with known model structure but uncertainty in the parameters of the process. The convenience of the proposed technique lies in the fact that historical operational data and/or a priori fault information is not required to achieve accurate fault reconstruction except for fixed, short intervals. The overall fault diagnosis algorithm is composed of a series of nonlinear estimators, which estimates parameter and a fault isolation and identification filter. Parameter estimation and fault reconstruction cannot be performed accurately since faults and parametric uncertainty interact with each other. Therefore, these two tasks are performed at different time scales, where the fault diagnosis takes place at a more frequent rate than the parameter estimation. It is shown that the fault can be reconstructed under some realistic assumptions and the performance of the proposed methodology is evaluated on a simulated chemical process exhibiting nonlinear dynamic behavior.

Algorithms↗

PubMed2004

Inhibition of mitochondrial gene transcription suppresses neurotensin secretion in the human carcinoid cell line BON.

Mitochondria, organelles essential for ATP production, play a central role in a number of cellular functions, including the regulation of insulin secretion. Neurotensin (NT), an important regulatory intestinal hormone, has been implicated in fatty acid translocation, gut motility and secretion, and intestinal cell growth; however, mechanisms regulating NT secretion have not been entirely defined. The purpose of this study was to determine the effect of inhibition of mitochondrial gene transcription on NT secretion. BON cells, a novel human carcinoid cell line that produces and secretes NT peptide and expresses the gene encoding NT (designated NT/N), were treated with ethidium bromide (EB; 0.05, 0.1, and 0.4 microg/ml), an inhibitor of DNA and RNA synthesis, or vehicle over a time course (1-4 days). Cells were then stimulated with either ACh (100 microM) or phorbol 12 myristate,13-acetate (PMA, 10 nM) for 30 min. Media and cells were extracted, and NT peptide measured by RIA. Treatment with EB had no effect on BON cell viability or cell cycle distribution over the 4-day course. In contrast, EB treatment produced a dose-dependent reduction of mitochondrial gene expression; however, NT/N gene expression was not altered. Mitochondrial inhibition by EB treatment suppressed NT secretion induced by ACh and PMA, both in a dose-dependent manner. EB-mediated inhibition of NT secretion and mitochondrial gene expression was reversed with removal of EB. Our results demonstrate that inhibition of mitochondrial gene transcription suppresses both ACh- and PMA-stimulated NT release. These findings are the first to demonstrate that mitochondrial function is important for agonist-mediated NT secretion.

Acetylcholine↗

PubMed2003

Differentiation-dependent expression of signal transducers and activators of transcription (STATs) might modify responses to growth factors in the cancers of the head and neck.

Overexpression of the epidermal growth factor receptor (EGFR) in the cancers of the head and neck is well demonstrated. In addition, copy numbers of the EGFR mRNA were significantly higher in poorly differentiated tumors than in tumors that had a differentiated phenotype. Studies by others also showed that the constitutively activated signal transducer and activator of transcription-3 (STAT3), but not STAT1, is required for EGFR-mediated cell growth. Our aim was to reveal if STAT expression is differentiation-dependent and thus, might respond to exogenous stimuli in a differentiation-dependent manner. Both reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry revealed that expression of STAT1 was high in well/moderately differentiated tumors in vivo. In contrast, STAT3 was expressed in poorly differentiated tumors. In vitro experiments showed that differentiated primary oral keratinocytes expressed higher levels of STAT1, but lower levels of STAT3 than did their undifferentiated counterparts. Epidermal growth factor treatment of oral keratinocytes with various degrees of differentiation showed the maximal induction of cyclin D1 in undifferentiated cells. Our findings suggest that the level of differentiation might modulate the outcome of EGFR signaling (i.e. cyclin D1 transcription), due to the differentiation-associated intracellular balance of transcriptional regulators (STAT1 versus STAT3).

Biopsy↗

PubMed2003

Late renal allograft rupture in a patient with small vessel vasculitis following discontinuation of immunosuppression.

We report the case of a 21-year-old man with antineutrophil cytoplasmic antibody (ANCA)--associated vasculitis who experienced spontaneous renal allograft rupture 21 months after engraftment. Because of chronic allograft nephropathy, the patient's immunosuppressive regimen had been discontinued approximately 3 weeks prior to his presentation with abdominal pain and evidence of internal hemorrhage. He was emergently taken to the operating room, where a ruptured allograft was found and transplant nephrectomy was performed. Postoperatively, the cause of rupture was determined to have been acute cellular rejection. This case may be the longest interval reported between renal transplant and spontaneous allograft rupture.

Adult↗

PubMed2003

Effect of ileocolonic transposition on gut morphology, gene expression, and function.

Intestinal morphology and expression of brush border enzymes can be dramatically altered by nutrient composition and position along the longitudinal gut axis. In contrast, endocrine gene expression appears to be relatively "imprinted" and is not significantly altered by positional changes. The purpose of our study was to assess the effects of transposing the ileum into the colonic position on intestinal morphology, gene expression, and enzyme activity. For this study, male Sprague-Dawley rats underwent either transposition of an approximately 8-cm segment of distal ileum into the colonic position or sham operation. Rats were sacrificed 2 months after operation and transposed or sham ileum was assessed. We found that transposition of the ileum to the colonic position resulted in no change in the ileal mucosal architecture. Furthermore, no change in the expression of the endocrine genes neurotensin and PYY or the apoptotic genes was detected. Although sucrase-isomaltase activity was decreased in the transposed ileum, this decrease did not achieve statistical significance. These results demonstrate that the ileum can be successfully interposed into the colonic position. In this location, the ileum functions normally without changes in the villus morphology or gene expression pattern despite the change in position and composition of the luminal content.

Animals↗

PubMed2003

The PPARgamma ligand, 15d-PGJ2, attenuates the severity of cerulein-induced acute pancreatitis.

INTRODUCTION: The prostaglandin D2 metabolite, 15d-PGJ2, a potent natural ligand for peroxisome proliferator-activated receptor gamma (PPARgamma), exerts antiinflammatory effects by inhibiting the induction of inflammatory response genes and NF-kappaB-dependent transcription. AIM To determine whether 15d-PGJ2 decreases the severity of secretagogue-induced acute pancreatitis (AP) and to assess cellular mechanisms contributing to these effects. METHODOLOGY Swiss Webster mice were injected with either saline or cerulein (50 microg/kg) hourly for 8 hours and received either 15d-PGJ2 (2 mg/kg) or vehicle 1 hour before and 4 hours after induction of AP. RESULTS Treatment with 15d-PGJ2 significantly attenuated AP, as determined by histologic assessment of edema, vacuolization, inflammation, and necrosis. This attenuation was associated with decreased cyclooxygenase-2 (COX-2) and intercellular adhesion molecule-1 (ICAM-1) expression and decreased serum and pancreatic IL-6 levels. Treatment with 15d-PGJ2 markedly inhibited NF-kappaB DNA-binding activity, and, moreover, this decreased activity was associated with a concomitant inhibition of IkappaB protein degradation. CONCLUSION Our findings demonstrate that 15d-PGJ2 attenuates the severity of AP most likely through the inhibition of COX-2 expression, IL-6 production, and NF-kappaB activation. Ligands specific for PPARgamma may represent novel and effective means of clinical therapy for AP.

Acute Disease↗

PubMed2002

Secondary resistance to cyclosporin A in children with nephrotic syndrome.

We investigated the phenomenon of secondary resistance to cyclosporin (CsA) in children with steroid dependent (SD) or steroid resistant (SR) nephrotic syndrome. Secondary resistance was defined as an initial response to CsA with relapse on withdrawal of therapy and absent or diminished response on reinstitution of the drug. Thirty-two children with nephrotic syndrome who were treated with CsA were included in the study. Twenty-two of the children (15 of 15 SD and 7 of 17 SR) responded while ten demonstrated primary CsA resistance. Of these 22 responders, 20 relapsed when therapy was tapered or discontinued. Cyclosporin was reinstituted in 19. Ten responded, demonstrating CsA dependence, and nine exhibited secondary CsA resistance. Focal segmental glomerular sclerosis (FSGS) was present in one patient with CsA dependence on the initial biopsy and in two of six on a subsequent biopsy. In comparison, seven of nine patients with secondary CsA resistance and ten of ten with primary CsA resistance had FSGS on the initial or subsequent biopsy ( P=0.03). C4 and/or C1q were present on the initial biopsy in one patient with CsA dependence as compared to six of nine with secondary CsA resistance ( P=0.02). Four patients with secondary CsA resistance had an accelerated progression to end-stage renal disease (ESRD). We conclude that the presence of FSGS, or of C4 and/or C1q, appears to increase the risk of secondary CsA resistance and some of these children rapidly progress to ESRD.

Alkylating Agents↗

PubMed2002

Selective inhibition of NF-kappaB attenuates the severity of cerulein-induced acute pancreatitis.

BACKGROUND: Acute pancreatitis (AP) is associated with increased cytokine production, which can ultimately produce deleterious local and systemic effects. The transcription factor NF-kappaB is activated by degradation of its inhibitory factor, IkappaB, and can stimulate various cytokines. The purpose of this study was to determine whether the inhibition of NF-kappaB binding activity with a novel peptide that binds to the NF-kappaB essential modifier binding domain (NBD) could attenuate the severity of AP. STUDY DESIGN: AP was induced in Swiss Webster mice by hourly injections of the cholecystokinin analogue cerulein (50 microg/kg). Mice were injected with either the wild-type or control (mutated) NBD peptide at the time of the first cerulein injection; they were then sacrificed over a time course, and pancreata and lungs were harvested for histologic analysis and scoring. Myeloperoxidase activity was measured to assess neutrophil sequestration as an indicator of inflammation. NF-kappaB binding activity and steady-state levels of IkappaB and NF-kappaB subunits were determined by gel shift and Western blot, respectively. RESULTS: AP resulted in increased NF-kappaB DNA-binding activity and decreased steady-state levels of IkappaB. Treatment with NBD peptide decreased inflammation in the pancreas, decreased hemorrhage in the lungs, and decreased myeloperoxidase activity in both pancreas and lung. CONCLUSIONS: The marked induction of NF-kappaB binding activity suggests a role for this transcription factor in the early inflammatory changes associated with AP. Treatment with the NBD peptide attenuated the severity of injury associated with AP. Novel compounds that selectively target NF-kappaB may prove to be useful treatment of AP and AP-associated lung injury.

Acute Disease↗

PubMed2002

Cyclooxygenase-2 gene disruption attenuates the severity of acute pancreatitis and pancreatitis-associated lung injury.

BACKGROUND & AIMS: Cyclooxygenase (COX) catalyzes the rate-limiting step in prostaglandin production; the inducible isoform, COX-2, has been implicated in a variety of inflammatory processes. The role of COX in acute pancreatitis and pancreatitis-associated lung injury is not known. METHODS: Acute pancreatitis was induced in Swiss Webster mice or mice deficient in the COX-2 (Ptgs2) or the COX-1 (Ptgs1) genes. Pancreata and lungs were harvested, and histologic sections of these tissues were scored. COX-2 expression, myeloperoxidase activity (a measurement of neutrophil sequestration), and serum amylase levels were determined. RESULTS: Acute pancreatitis was associated with induction of COX-2 expression. Treatment with NS-398 (a COX-2 inhibitor) significantly decreased the severity of pancreatitis. Furthermore, Ptgs2-deficient mice showed minimal histologic evidence of pancreatitis, a marked attenuation in the severity of lung injury, and a significant reduction in myeloperoxidase activity. In contrast, Ptgs1-deficient mice had pancreatitis and pulmonary inflammation, which was as severe or, in some instances, more severe than in the wild-type mice. CONCLUSIONS: Inhibition of COX-2 by either pharmacologic inhibition or selective genetic deletion markedly attenuated the severity of acute pancreatitis. Our findings identify the COX-2 isoform as an important regulator of the severity of acute pancreatitis and pancreatitis-associated lung injury.

Acute Disease↗

PubMedDate not supplied

COX-2 inhibition results in alterations in nuclear factor (NF)-kappaB activation but not cytokine production in acute pancreatitis.

Acute pancreatitis is characterized by local inflammation and cytokine production, and release is thought to contribute to this process. Nuclear factor (NF)-kappaB activation and cytokine production are linked and inhibition of NF-kappaB has been shown to decrease the severity of pancreatitis. We have shown that inhibition of COX-2 ameliorates pancreatitis; however, the mechanism by which this effect occurs is unclear. Swiss Webster mice were injected intraperitoneally with either saline (control) or caerulein (CAE; 50 mg/kg) hourly for 8 hours; mice receiving CAE were further subdivided to receive saline or the cyclooxygenase-2 (COX-2) selective inhibitor (SC-58125; 10 mg, intraperitoneally) at the time of the first injection of CAE. Pancreata were harvested, histologic sections were scored, and protein was extracted to determine cytokine (interleukin [IL]-6, IL-1beta) levels and NF-kappaB subunits by ELISA and NF-kappaB activation by gel shift. In addition, serum was collected for measurement of cytokines. COX-2 inhibition resulted in decreased inflammation and a decrease in NF-kappaB activation. IL-6 and IL-1beta levels after COX-2 inhibition, however, remained elevated to levels equivalent to those of mice with histologic inflammation after CAE alone. COX-2 inhibition decreases inflammation as well as late-phase NF-kappaB activation but does not diminish levels of inflammatory cytokines, thus suggesting a two-phase activator of NF-kappaB. The attenuation of inflammation, despite unaltered cytokine levels, suggests that cytokines may not be critical for the inflammatory phase of pancreatitis.

Acute Disease↗