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Marc D Basson

Publications and source records attributed to Marc D Basson.

At least 37 records · Page 2Linked to original sources
PubMed2004

Extracellular pressure stimulates macrophage phagocytosis by inhibiting a pathway involving FAK and ERK.

We hypothesized that changes in extracellular pressure during inflammation or infection regulate macrophage phagocytosis through modulating the focal adhesion kinase (FAK)-ERK pathway. Undifferentiated (monocyte-like) or PMA-differentiated (macrophage-like) THP-1 cells were incubated at 37 degrees C with serum-opsonized latex beads under ambient or 20-mmHg increased pressure. Pressure did not affect monocyte phagocytosis but significantly increased macrophage phagocytosis (29.9 +/- 1.8 vs. 42.0 +/- 1.6%, n = 9, P < 0.001). THP-1 macrophages constitutively expressed activated FAK, ERK, and Src. Exposure of macrophages to pressure decreased ERK and FAK-Y397 phosphorylation (77.6 +/- 7.9%, n = 7, P < 0.05) but did not alter FAK-Y576 or Src phosphorylation. FAK small interfering RNA (SiRNA) reduced FAK expression by >75% and the basal amount of phosphorylated FAK by 25% and significantly increased basal macrophage phagocytosis (P < 0.05). Pressure inhibited FAK-Y397 phosphorylation in mock-transfected or scrambled SiRNA-transfected macrophages, but phosphorylated FAK was not significantly reduced further by pressure in cells transfected with FAK SiRNA. Pressure increased phagocytosis in all three groups. However, FAK-SiRNA-transfected cells exhibited only 40% of the pressure effect on phagocytosis observed in scrambled SiRNA-transfected cells so that phagocytosis inversely paralleled FAK activation. PD-98059 (50 microM), an ERK activation inhibitor, increased basal phagocytosis (26.9 +/- 1.8 vs. 31.7 +/- 1.1%, n = 15, P < 0.05), but pressure did not further increase phagocytosis in PD-98059-treated cells. Pressure also inhibited ERK activation after mock transfection or transfection with scrambled SiRNA, but transfection of FAK SiRNA abolished ERK inhibition by pressure. Pressure did not increase phagocytosis in MonoMac-1 cells that do not express FAK. Increased extracellular pressure during infection or inflammation enhances macrophage phagocytosis by inhibiting FAK and, consequently, decreasing ERK activation.

Cell Line↗
PubMed2004

Effect of four-day psyllium supplementation on bowel preparation for colonoscopy:A prospective double blind randomized trial [ISRCTN76623768].

BACKGROUND: Patients with new onset constipation or presumed hemorrhoid bleeding frequently require the use of both fiber supplements and diagnostic colonoscopy. We sought to determine whether preliminary fiber supplementation would alter the tolerability or efficacy of a standard bowel preparation for colonoscopy METHODS: A prospective, double blind, randomized trial was designed to compare a short course of a psyllium-based supplement versus placebo prior to a colon lavage. Patients were given an unlabeled canister of powder, and instructed to take 1 tablespoon with 8 oz of water bid for 4 days before colonoscopy. A 4-liter polyethylene based glycol lavage was self-administered over 4 hours on the day prior to colonoscopy. A questionnaire on pre-study bowel habits and side effects was completed. Efficacy of the preparation was visually evaluated on a pre-determined scale. RESULTS: There were no significant differences between the two groups in gender, race, age, pre-study stool frequency or consistency. Tolerability was equivalent but efficacy of the bowel preparation was worse in the psyllium group compared to placebo (P < 0.05). CONCLUSIONS: In non-constipated patients psyllium based fiber supplementation should not be initiated in the few days prior to endoscopy using a polyethylene glycol preparation.

Cathartics↗
PubMed2004

Paradigms for mechanical signal transduction in the intestinal epithelium. Category: molecular, cell, and developmental biology.

Diverse physical forces including deformation or strain, pressure, and shear stress affect the intestinal mucosa during normal function, and mucosal biology is altered in pathological states in which these forces alter. Taken together with evidence in other tissues and cell types that physical forces can affect cell biology, this has led to the hypothesis that repetitively applied physical forces can initiate intracellular signals that alter intestinal epithelial proliferation and phenotype. This review outlines the nature of such forces and summarizes in vivo and in vitro evidence in support of the paradigm that repetitive force is trophic for the intestinal mucosa via a complex cascade of intracellular signals.

Biomechanical Phenomena↗
PubMed2004

Informed consent for screening sigmoidoscopy in a Veterans Administration population.

PURPOSE: This study was performed to test the hypotheses that current consent methods may not convey the data that we imagine that they do, and that many patients may not want the data that we believe that we ought to provide. We also argue that excessive and unthinking emphasis on informed consent documentation may ignore real and important issues. METHODS: Fifty-nine male patients consecutively scheduled for screening sigmoidoscopy were interviewed before and after the procedure in a tertiary care academic health center. Chi-squared analysis was used to determine if the three independent variables of ethnicity, educational level, and previous sigmoidoscopy experience were able to discriminate various components of the informed consent process. RESULTS: Thirty-nine percent of patients could describe no indication other than doctor recommendation for the procedure. Although 86 percent of patients had heard of the word "polyp," 16 percent could not define it. Fifteen percent of patients could not pick out from a list subsequent steps to be taken in case of an abnormal examination. Although most patients could describe discomforts associated with the procedure, only 19 percent of patients mentioned bleeding and perforation as possible complications. Only 5 percent of patients knew any alternatives to sigmoidoscopy. No patient could explain risks and benefits of alternatives. Eighty-eight percent of patients could not identify their endoscopist, but this only bothered 13 percent. Ninety-three percent of patients were given an opportunity to ask questions, but only 22 percent actually did so. All patients signed the consent form, but only 14 percent of patients actually read all of it. Most patients, 97 percent, thought that they had enough information to proceed with the endoscopy. CONCLUSIONS: By traditional and classic standards, the patients in this study did not give informed consent. Yet, surprisingly, despite this lack of informed consent, most of the patients failed to ask further questions of their physicians and claimed that they had sufficient information to proceed with the procedure. This was the case across the three independent variables of ethnicity, educational level, and previous sigmoidoscopy experience.

Aged↗
PubMed2004

Extracellular pressure stimulates colon cancer cell adhesion in vitro and to surgical wounds by Src (sarcoma protein) activation.

BACKGROUND: We hypothesized that pressure stimulates colon cancer cell adhesion to surgical wounds. METHODS: We quantitated adhesion of murine 26/51 transplantable colon cancer cells by cell counting or chromium 51-labeling. Tumor cells were added to murine surgical wounds after 30 minutes preincubation under ambient or 15 mm Hg increased pressure. Src activation was assayed by immunoblotting for phosphorylated Src and inhibited by 4-amino-5-(4chlorophenyl)-7-(t-butyl)pyrazolo-[3-4-d]pyrimidine (PP2). RESULTS: Pressure stimulated colon 26/51 cell adhesion to murine wounds by 43% to 52% (n = 9, P <0.05 each). Pressure stimulated Src phosphorylation by 39% +/- 4% (n = 5, P = 0.004) in colon 26 cells. The Src inhibitor PP2 (20 mumol/L) did not inhibit Src phosphorylation at ambient pressure but prevented pressure stimulation of Src phosphorylation. Src blockade by PP2 did not affect basal adhesion of either tumor to murine wounds but completely blocked pressure stimulation of adhesion (n = 4, P <0.001 each). CONCLUSIONS: Increased pressure may activate cancer adhesion to surgical wounds via Src. Src antagonists might inhibit this process.

Animals↗
PubMed2004

Pressure alters endothelial effects upon vascular smooth muscle cells by decreasing smooth muscle cell proliferation and increasing smooth muscle cell apoptosis.

BACKGROUND: Although de-endothelialization after vascular intervention is associated with intimal hyperplasia, endothelial cells (ECs) increase smooth muscle cell (SMC) numbers in conventional cocultures. In previously published work, SMCs cocultured with ECs in a chronic high-pressure environment exhibited significantly decreased cell counts compared to monocultured SMCs in the same high pressure. This finding contrasted with SMCs cocultured with ECs in ambient pressure, which exhibited significantly higher cell counts than the monocultured SMCs in ambient pressure. We now hypothesize that extracellular pressure decreases SMC number during coculture with ECs by decreasing SMC proliferation through nuclear protein regulation and by increasing SMC apoptosis. Furthermore, this effect depends on the EC response to pressure. METHODS: Rat aortic SMCs were cultured independently (SMC/0) or cocultured with EC (SMC/EC) under either atmospheric or increased pressure (130-135 mmHg over ambient, SMC/0-P and SMC/EC-P) for 5 days. We assessed SMC proliferative potential by determining c-myc expression (by protein analysis), apoptosis (by cell counting, staining with acridine orange or TUNEL technique), and topoisomerase IIalpha levels. Parallel studies measured the effects of conditioned media from monocultured EC and SMC exposed for 5 days to control or increased pressure on recipient SMC growing in conventional culture. RESULTS: In high-pressure conditions, SMC/EC-P exhibited 42% less c-myc expression than SMC/0s (P = .00028). Significantly increased apoptotic activity (22 +/- 1.8%) in SMC/EC-Ps compared to SMC/0s was coupled with significantly lower topoisomerase IIalpha levels. Interestingly, pressure (SMC/0-P) and EC coculture (SMC/EC) each separately raised myocyte apoptotic activity to 15 +/- 1.3% and 17 +/- 2.0%, respectively. Conditioned media from pressurized ECs caused a 20% decrease in cell counts in target SMC compared to conditioned media from ECs in atmospheric pressure. Media from pressurized SMCs did not affect target SMCs. CONCLUSIONS: In a model designed to study SMC/EC interactions in a dynamic environment, EC exposure to pressure alters the growth characteristics and apoptotic activity of SMCs via a secreted factor. Extracellular pressure may alter EC regulation of SMC behavior and regulate intimal hyperplasia.

Animals↗
PubMed2004

Pressure activates colon cancer cell adhesion by inside-out focal adhesion complex and actin cytoskeletal signaling.

BACKGROUND AND AIMS: Few circulating tumor cells implant or cause metastasis. We hypothesized that venous or lymphatic pressure or iatrogenic pressure during resection activates signals governing malignant colonocyte adhesion. METHODS: We studied the effect of 15 mm Hg increased pressure for 30 minutes on adhesion of primary human colon cancer cells and SW620 colonocytes to collagen and endothelial cells. We modulated integrin affinity with extracellular cations. We assessed binding affinity by detachment assay; integrin surface expression by flow cytometry; and focal adhesion kinase (FAK), Src, and extracellular signal-regulated kinase (ERK) activation by Western analysis and Src in vitro kinase assay. We inhibited Src (PP2), FAK (small RNA interference, SiRNA, or FRNK transfection), MEK (PD98059), PKC (calphostin C), and actin destabilization (phalloidin). RESULTS: Pressure and manganese stimulated primary and SW620 colonocyte adhesion to collagen. Pressure also stimulated SW620 adhesion to endothelial monolayers. Pressure strengthened SW620 binding force to matrix without changing integrin surface expression. Pressure activated SW620 FAK and Src, but not ERK. Manganese did not. Calcium-inhibited adhesion but stimulated FAK (but not Src). PP2 prevented pressure activation of Src, Src phosphorylation of FAK576, and pressure-stimulated adhesion but not FAK397 autophosphorylation. FRNK transfection or FAK SiRNA also prevented pressure-stimulated adhesion. FAK SiRNA ablated pressure-activated FAK397, Src, and FAK576 phosphorylation. Neither Src nor FAK inhibition blocked cation effects. Phalloidin prevented pressure-stimulated adhesion. PD98059 or calphostin C did not. CONCLUSIONS: In contrast to divalent cations, extracellular pressure may increase integrin affinity and promote colon cancer adhesion via actin dependent inside-out FAK and Src signals. This mechanotransduced pathway may regulate metastasizing tumor cell adhesion.

Actins↗
PubMed2004

The Greenfield filter as a potential hazard to the operating surgeon.

The Greenfield filter and similar devices are placed in the vena cava of patients who have contraindications to anticoagulation, but who would otherwise be at risk of pulmonary embolism without such anticoagulation. Injury to a health care worker from one of these devices has been reported in the case of a pathologist performing a necropsy. To the author's knowledge, injury or near-injury to a member of the surgical team during operation has not been reported in the literature. The authors report on a near-miss injury from such a device to the surgical first assistant during the performance of a pancreaticoduodenectomy. Simple guidelines to avoid similar injuries are provided.

Accidents, Occupational↗
PubMed2003

Collagen IV regulates Caco-2 migration and ERK activation via alpha1beta1- and alpha2beta1-integrin-dependent Src kinase activation.

Our previous work indicates intestinal epithelial cell ERK activation by collagen IV, a major component of the intestinal epithelial basement membrane, requires focal adhesion kinase (FAK) and suggests FAK and ERK may have important roles in regulating intestinal epithelial cell migration. We therefore sought to identify FAK downstream targets regulating intestinal epithelial cell spreading, migration, and ERK activation on collagen IV and the integrins involved. Both dominant-negative Src and Src inhibitor PP2 strongly inhibited collagen IV ERK activation in Caco-2 intestinal epithelial cells. Collagen IV stimulated Grb2 binding site FAK Y925 phosphorylation, which was inhibited by PP2 and required FAK Y397 autophosphorylation. Additionally, FAK Y925F expression blocked collagen IV ERK activation. alpha(1)beta(1)- Or alpha(2)beta(1)-integrin blockade with alpha(1)- or alpha(2)-integrin subunit antibodies indicated that either integrin can mediate adhesion, cell spreading, and FAK, Src, and ERK activation on collagen IV. Both dominant-negative Src and PP2 inhibited Caco-2 spreading on collagen IV. PP2 inhibited p130(Cas) tyrosine phosphorylation, but dominant-negative p130(Cas) did not inhibit cell spreading. PP2 inhibited Caco-2 migration on collagen IV much more strongly than the mitogen-activated protein kinase kinase inhibitor PD-98059, which completely inhibited collagen IV ERK activation. These results suggest a pathway for collagen IV ERK activation requiring Src phosphorylation of FAK Y925 not previously described for this matrix protein and suggest either alpha(1)beta(1)- or alpha(2)beta(1)-integrins can regulate Caco-2 spreading and ERK activation on collagen IV via Src. Additionally, these results suggest Src regulates Caco-2 migration on collagen IV primarily through ERK-independent pathways.

Antibodies, Blocking↗
PubMed2003

Fibronectin blocks p38 and jnk activation by cyclic strain in Caco-2 cells.

Diverse repetitive forces deform the intestinal epithelium and basement membrane. Such repetitive deformation induces intestinal epithelial proliferation, differentiation, and intracellular signaling. Although at least some deformation-induced signals probably involve integrins, the matrix-dependence of these signals is poorly understood. We compared rapid strain activation of p38 and jnk in human Caco-2 intestinal epithelial cells cultured on collagen I, collagen IV, laminin, and tissue fibronectin. These signals were inhibited in cells on a fibronectin substrate, but activated by strain on collagens and laminin. Furthermore, adding 300 microg/ml plasma fibronectin (approximately the concentration found in plasma) to the culture medium inhibited strain activation of p38 and jnk in cells cultured on collagen. Since tissue and plasma fibronectin levels vary in acute or chronic inflammatory or infectious conditions, these results suggest that tissue or plasma fibronectin may modulate the intestinal epithelial response to repetitive deformation.

Caco-2 Cells↗
PubMed2003

Regulation of the intestinal epithelial response to cyclic strain by extracellular matrix proteins.

Repetitive mechanical deformation may stimulate intestinal epithelial proliferation. Because the extracellular matrix modulates static intestinal epithelial biology, we examined whether matrix proteins influence intestinal epithelial responses to deformation. Human Caco-2BBE cells and nontransformed human enterocytes (HIPEC) were subjected to 10% average cyclic strain at 10 cycles/min on flexible membranes precoated with matrix proteins without or with plasma fibronectin or functional anti-integrin antibodies in the medium. Strain stimulated proliferation, focal adhesion kinase, extracellular signal-regulated protein kinase (ERK), p38, and Jun N-terminal kinase similarly on collagen I or IV, and more weakly on laminin, but had no effect on fibronectin. MEK blockade (PD98059) prevented strain-stimulated proliferation on collagen but did not affect proliferation on fibronectin. Adding tissue fibronectin to a collagen substrate or plasma fibronectin to the media suppressed strain s mitogenic and signal effects, but not those of epidermal growth factor. Functional antibodies to the alpha5 or alpha(v) integrin subunit blocked strain's effects on Caco-2 proliferation and ERK activation, although ligation of the alpha2 or alpha6 subunit did not. Repetitive strain also stimulated, and fibronectin inhibited, human intestinal primary epithelial cell proliferation. Repetitive deformation stimulates transformed and nontransformed human intestinal epithelial proliferation in a matrix-dependent manner. Tissue or plasma fibronectin may regulate the intestinal epithelial response to strain via integrins containing alpha5 or alpha(v).

Caco-2 Cells↗
PubMed2003

Caspase activation may be associated with Mycobacterium avium pathogenicity.

BACKGROUND: Mycobacterium avium causes disseminated infection in immunocompromised patients and triggers a process resembling Crohn's disease in goats. Colony morphotypes predict pathogenicity. Smooth-transparent (SmT) morphotypes are more virulent and induce less interleukin (IL)-1beta and IL-18 production than avirulent smooth-domed (SmD) morphotypes. Caspases are essential for IL-1beta and IL-18 production. METHODS: Caspase activation was examined in human monocytes after M. avium infection. RESULTS: Fresh monocytes constitutively expressed caspase-1 mRNA and pro-caspase-1. The M. avium infection increased monocyte caspase-1 mRNA expression. Furthermore, SmD-infected monocytes expressed 2.3-fold higher levels (P <0.05, n = 3) of activated caspases than SmT-infected monocytes. Caspase-1 inhibition significantly reduced IL-1beta production by SmT- and SmD-infected monocytes (P <0.05, n = 4). Caspase-3 inhibition inhibited IL-1beta production 43.5% +/- 8.0% (P <0.02, n = 4) by SmD-infected but not SmT-infected monocytes. CONCLUSIONS: Decreased mature IL-1beta release by SmT-infected monocytes may reflect selective induction of caspase-1 activity but not caspase-3. Differential caspase expression in monocytes after infection may contribute to M. avium pathogenicity in humans.

Blotting, Western↗
PubMed2003

Chronic high pressure potentiates the antiproliferative effect and abolishes contractile phenotypic changes caused by endothelial cells in cocultured smooth muscle cells.

UNLABELLED: High in vitro pressures have been reported to alter smooth muscle cell (SMC) and endothelial cell (EC) phenotype, while endothelial cells (ECs) can influence the proliferation, phenotype, and contractile features of smooth muscle cells (SMC) in coculture systems. However, little is known about the in vitro effects of pressure on EC/SMC cocultures. We therefore sought to compare SMC proliferation in independent and EC coculture under ambient and high pressure, and identify changes in the contractile phenotype of SMCs by measuring levels of the L-type Ca(2+) channel a(1) subunit (dihydropyridine-DHP receptor) which is critical for Ca(2+) transients, differentiation and contractility in SMC. METHODS: Rat aortic SMCs in independent culture (SMC/0) and coculture with ECs (SMC/EC) were maintained in 5% CO(2) under either atmospheric or high pressure (130 mmHg). SMC were counted at 0, 1, 3, and 5 days and compared to initial cell counts of day 0 before the exposure to experimental conditions. DHP receptor levels were quantitated by Western blotting (three similar studies). RESULTS: ECs suppressed SMC proliferation on day 1 of coculture in both atmospheric and high pressure (20% inhibition vs independent culture, P < or = 0.05). By day 3, cocultured SMC under atmospheric pressure displayed no EC-mediated inhibition, and at day 5, atmospheric cocultured SMCs revealed statistically significant enhanced proliferation as compared with SMCs in independent cultures. However, cocultured SMCs exposed to 130 mmHg pressure displayed sustained sensitivity to EC growth inhibition at both days 3 and 5 of the experiment. Coculture decreased SMC DHP-receptor levels under atmospheric pressure. However, this effect was abolished in cocultures exposed to high pressure. CONCLUSIONS: High pressure substantially alters the regulatory influence of EC on SMC proliferation and contractile potential. This pressure/coculture model should increase our understanding of cellular interaction in hypertensive vasculopathy.

Animals↗
PubMed2003

Divalent cations modulate human colon cancer cell adhesion.

BACKGROUND: Iatrogenic tumor implantation within surgical sites can compromise curative cancer surgery. Cancer cell adhesion to extracellular matrix proteins is mediated by diverse matrix receptors, most notably integrins. Divalent cations may modulate integrin-ligand interactions in some cells. MATERIALS AND METHODS: We studied adhesion of SW620 and Caco-2 human colon cancer cells to collagen I, the dominant collagen of the interstitial matrix, and confirmed our results in primary human colon cancer cells from surgical specimens. Single cell suspensions in either HEPES/NaCl buffer or media supplemented with 0-1 mM Mn2+ or Mg2+, and 0-10 mM Zn2+ or Ca2+ were plated onto collagen-I-precoated dishes for 30 min. RESULTS: Supplementation of the HEPES/NaCl/BSA buffer with 1 mM Mn2+, Mg2+, Zn2+, or Ca2+ affected adhesion differently. Mn2+ (1 mM) markedly promoted SW620 adhesion vs control (21.17 +/- 0.08-fold). Mg2+ (1 mM) had a similar but lesser effect (14.71 +/- 0.02-fold). However, 1-10 mM Ca2+ inhibited basal cell adhesion by 22.0 +/- 3.1 to 88.0 +/- 7.3 % inhibition. Ca2+ (2.5-10 mM) also inhibited Mn2+-induced adhesion. Zn2+ stimulated basal adhesion slightly at lower concentrations but inhibited Mn2+-stimulated adhesion similarly to Ca2+ at higher concentrations. Results were duplicated in conventional serum containing culture medium supplemented with these cations. Caco-2 cells and primary cancer cells yielded similar results. All results are significant to P < 0.01. DISCUSSION: Integrin-mediated colon cancer cell adhesion is affected by extracellular divalent cation concentrations. Washing the surgical site with dilute calcium or zinc solutions might diminish perioperative tumor implantation.

Adenocarcinoma↗
PubMed2002

Repetitive deformation and pressure activate small bowel and colonic mucosal tyrosine kinase activity in vivo.

Physical forces like deformation and pressure modulate signaling and phenotype in cultured cells. However, it is more difficult to establish that such phenomena occur in vivo. We studied the effects of 0 to 10 minutes of rhythmic distension with an isotonic electrolyte and polyethylene glycol solution to 30 cm H(2)O pressure on defunctionalized small and large bowel segments in adult male Sprague Dawley rats. Mucosa was harvested at 0, 1, and 10 minutes and assayed for tyrosine kinase activity. Rhythmic distension caused a time-dependent increase in colonic mucosal tyrosine kinase activity, which was statistically significant at 10 minutes (140% +/- 41% increase, n = 5, P <.05). Small bowel tyrosine kinase activity was markedly lower than that observed in the colon, but achieved a statistically significant increase at 5 minutes after initiation of rhythmic distension. (115% +/- 44% increase, n = 5, P <.05).

Animals↗