Induction of the proliferative phenotype in differentiated myogenic cells by hypoxia

The role of apoptosis on trophoblast cell invasion in the placental bed of normotensive and preeclamptic pregnancies

BACKGROUND

Placental development depends on careful coordination of trophoblast proliferation and apoptosis; however, the synchrony of its effect on trophoblast invasion is unknown.

OBJECTIVE

To examine the relationship between trophoblast apoptosis and proliferation in placental bed tissue of preeclamptic and normotensive pregnancies.

METHODS

Serial sections from archived placental bed biopsies of 12 normotensive (group 1) and 12 preeclamptic (group 2) were immunolabeled with a rabbit anti-Ki67 antibody, a mouse anti-cytokeratin 18 and its neo-epitope, and a monoclonal cytodeath M30 antibody.

RESULTS

The immunoexpression of Ki67 for all trophoblast cell subpopulations within the myometrium was non-reactive in both study groups. Smooth muscle cells of the microvasculature reflected a moderate degree of proliferation in both groups. Morphometric image analysis of the wall of the spiral artery revealed a mean area of 31,1729 ± 51,180 µm(2) compared to 35,795 ± 8045 µm(2) in groups 1 and 2, respectively. An elevation of intramural trophoblast was evident within the spiral artery of group 1 (13%). Comparative analyses of M30 distribution on corresponding serial sections were 0.06% versus 0% in groups 1 and 2, respectively. The mean field area percentage of interstitial trophoblast invasion was 10.79% versus 2.87% with corresponding areas of apoptosis been 0.8 % versus 1.9 % in groups 1 and 2, respectively.

CONCLUSIONS

This study demonstrates an increased trophoblast apoptosis in placental bed of preeclamptic compared to normotensive pregnancies with concurrent absence of proliferation at term.

Endovascular intervention for renal artery stenosis

Renovascular diseases are common conditions with important implications on cardiovascular morbidity and mortality. Renal artery stenosis (RAS) is present in 1-5% of patients with hypertension (HTN) in the US with the vast majority of caused by atherosclerosis. Atherosclerotic RAS is related not only to uncontrolled HTN, but also to renal dysfunction. Atherosclerotic RAS in the USA has been reported to account for approximately 14-16% of new patients requiring dialysis each year. Hence a concerted effort was made in the last decade to treat renovascular stenosis using newly developed endovascular therapies to improve cardiovascular morbidity and renal function. A review on new advances in the endovascular management of renal artery stenosis with low profile stents, embolic protection devices, and drug eluting stents is presented.

Effect of Low Glutamine/Glucose on Hypoxia-Induced Elevation of Hypoxia-Inducible Factor-1 in Human Pancreatic Cancer MiaPaCa-2 and Human Prostatic Cancer DU-145 Cells

PURPOSE AND EXPERIMENTAL DESIGN

Tumor microenvironment is characterized by regions of fluctuating and chronic hypoxia, low extracellular pH, and nutrient depletion. Although it is well known that hypoxia stimulates the accumulation of hypoxia-inducible factor-1alpha (HIF-1alpha), the role of low extracellular pH and nutrient depletion on hypoxia up-regulation of HIF-1alpha is not well known. In this study, human pancreatic cancer MiaPaCa-2 and human prostatic cancer DU-145 cells were exposed to hypoxia in the presence or absence of glucose, glutamine, and/or pyruvate.

RESULTS

We observed that low glucose and low glutamine, but not low pyruvate, effectively suppressed the elevation of HIF-1alpha level during hypoxia (0.1-1% oxygen). Deprivation of glutamine or glucose inhibited the accumulation of HIF-1alpha in the presence of MG-132, a protease inhibitor, regardless of oxygen tensions. Data from reverse transcription-PCR analysis revealed that the levels of HIF-1alpha mRNA were not significantly changed at different concentrations of glutamine or glucose under hypoxia. The amount of HIF-1alpha suppression was proportional to protein synthesis inhibition.

CONCLUSIONS

Our data suggest that glutamine or glucose deprivation inhibits the accumulation of HIF-1alpha under hypoxic conditions by disrupting translational processes rather than transcriptional or proteasomal degradation processes.

Growth and cellular differentiation: a physico-biochemical conundrum? The example of the hand

Currently, the predominant hypothesis explains cellular differentiation as an essentially genetic intracellular process. The goal of this paper is to suggest that cell growth and differentiation may be, simply, the result of physical and chemical constraints. Bone growth occurs at the level of cartilage conjunction (growth plate) in a zone of lesser constrain. It appears that this growth also induces muscle, tendon, nerve and skin elongation. This cartilage growth by itself seems to explain the elongation of the hand. Growth stops at puberty likely because of feed-back from an increasing muscle load. The ossification (that is differentiation of cartilage into bone) appears to result from the shear stress induced. The study of bone age, obtained by X-ray picture of the hand, shows that ossification of epiphyses is very precise both in time and space. Computer modelization suggests that this ossification occurs where shear stress is greatest. The cartilage which does not ossify (joint, nose, larynx, ear, bronchus, etc.) is not exposed to high shear. Shear stress induces the secretion of extracellular matrix and a change of the biochemical environment of the cell. Precipitation of calcium phosphate, as in ossification, seems related to the alkalosis induced by shear stress. To speak in more general terms, loss of cellular differentiation, as occurs with cancer, can result from a change in the physical-chemical environments.

Effects of hypoxia on rat airway smooth muscle cell proliferation

Although it is well known that hypoxemia induces pulmonary vasoconstriction and vascular remodeling, due to the proliferation of both vascular smooth muscle cells and fibroblasts, the effects of hypoxemia on airway smooth muscle cells are not well characterized. The present study was designed to assess the in vitro effects of hypoxia (1 or 3% O(2)) on rat airway smooth muscle cell growth and response to mitogens (PDGF and 5-HT). Cell growth was assessed by cell counting and cell cycle analysis. Compared with normoxia (21% O(2)), there was a 42.2% increase in the rate of proliferation of cells exposed to 3% O(2) (72 h, P = 0.006), as well as an enhanced response to PDGF (13.9% increase; P = 0.023) and to 5-HT (17.2% increase; P = 0.039). Exposure to 1% O(2) (72 h) decreased cell proliferation by 21.0% (P = 0.017) and reduced the increase in cell proliferation induced by PGDF and 5-HT by 16.2 and 15.7%, respectively (P = 0.019 and P = 0.011). A significant inhibition in hypoxia-induced cell proliferation was observed after the administration of bisindolylmaleimide GF-109203X (a specific PKC inhibitor) or downregulation of PKC with PMA. Pretreatment with GF-109203X decreased proliferation by 21.5% (P = 0.004) and PMA by 31.5% (P = 0.005). These results show that hypoxia induces airway smooth muscle cell proliferation, which is at least partially dependent on PKC activation. They suggest that hypoxia could contribute to airway remodeling in patients suffering from chronic, severe respiratory diseases.

Replicating adenoviral vector-mediated transfer of a heat-inducible double suicide gene for gene therapy

Tumor cells that express a fusion gene of Escherichia coli cytosine deaminase (CD) and herpes simplex virus type 1 thymidine kinase (TK) sequences activate and are subsequently killed by the nontoxic prodrugs 5-fluorocytosine and ganciclovir. We have previously developed a recombinant adenovirus containing the CD-TK fusion gene controlled by the human inducible heat shock protein 70 promoter so that heat at 41 degrees C for 1 hour induces therapeutic gene expression. This adenovirus effectively transduces heat-inducible expression of the CD-TK gene into human prostate carcinoma cells. However, because a limited number of cells in a tumor can actually be infected, we created a replicating adenoviral vector to increase CD-TK gene expression. This vector is a replication-competent, E1B-attenuated adenoviral vector containing the hsp70 promoter-driven CD-TK gene (Ad.E1A(+)HS-CDTK). When human prostate adenocarcinoma DU-145 cells (mutant p53) were infected with the virus at a multiplicity of infection (MOI) of 1 or 10, the viral replication was detected within 2 days at both MOIs. Similar results were observed in human colorectal carcinoma CX-1 cells. When DU-145 cells were infected with the virus at an MOI of 10, incubated for 24 hours, heated at 41 degrees C for 4 hours, and then harvested 20 hours later, Western blot analysis demonstrated that this virus successfully produced viral E1A proteins and heat shock stimulated the CD-TK gene expression by 12.3-fold. In addition, Ad.E1A(+)HS-CDTK effectively suppressed cell proliferation by viral cytopathic effect). Unlike with a replication-incompetent virus (Ad.HS-CDTK), the cytopathic effect of the virus and cytotoxicity in the presence of the prodrugs were still observed even at low MOI (MOI=1.0).

Hypoxia stimulates osteopontin expression and proliferation of cultured vascular smooth muscle cells: potentiation by high glucose

We examined the effect of hypoxia on proliferation and osteopontin (OPN) expression in cultured rat aortic vascular smooth muscle (VSM) cells. In addition, we determined whether hypoxia-induced increases in OPN and cell proliferation are altered under hyperglycemic conditions. Quiescent cultures of VSM cells were exposed to hypoxia (3% O(2)) or normoxia (18% O(2)) in a serum-free medium, and cell proliferation as well as the expression of OPN was assessed. Cells exposed to hypoxia for 24 h exhibited a significant increase in [(3)H]thymidine incorporation followed by a significant increase in cell number at 48 h in comparison with respective normoxic controls. Exposure to hypoxia produced significant increases in OPN protein and mRNA expression at 2 h followed by a gradual decline at 6 and 12 h, with subsequent significant increases at 24 h. Neutralizing antibodies to either OPN or its receptor beta3 integrin but not neutralizing antibodies to beta5 integrin prevented the hypoxia-induced increase in [(3)H]thymidine incorporation. Inhibitors of protein kinase C (PKC) and p38 mitogen-activated protein (MAP) kinase also reduced the hypoxia-induced stimulation of proliferation and OPN synthesis. Exposure to high-glucose (HG) (25 mmol/l) medium under normoxic conditions also resulted in significant increases in OPN protein and mRNA levels as well as the proliferation of VSM cells. Under hypoxic conditions, HG further stimulated OPN synthesis and cell proliferation in an additive fashion. In conclusion, hypoxia-induced proliferation of cultured VSM cells is mediated by the stimulation of OPN synthesis involving PKC and p38 MAP kinase. In addition, hypoxia also enhances the effect of HG conditions on both OPN and proliferation of cultured VSM cells, which may have important implications in the development of diabetic atherosclerosis associated with arterial wall hypoxia.

The calcium inhibitor SR33805 reduces intimal formation following injury of the porcine carotid artery

We studied the effect of SR33805, a calcium channel blocker, in vitro on the proliferation of vascular smooth muscle cells (SMC) stimulated by foetal calf serum, basic fibroblast growth factor and platelet derived growth factor, and in vivo with regard to SMC migration and proliferation which occurred following injury of the porcine carotid artery. The intimal lesion was induced by a silasten collar surgically positioned around the carotid artery and by a stenosis reducing blood flow by 50% for 30 days. Animals received SR33805 (5 mg/kg/day) 8 days before the induction of the lesion and up to 30 days after. In vitro, SR33805 inhibited in a dose-dependent manner growth factor-induced proliferation of SMC (0.20<IC(50)<0.46 microM). In vivo, SR33805 reduced the intima/media ratio of the cross sectional surface area (decrease of 60%, P<0.05) without affecting neointimal SMC density. The medial SMC density was 40% lower in treated than in control animals (upstream, P<0.05 and downstream to the stenosis, P<0.01). Thus, it appears that SR33805 significantly reduced intimal hyperplasia, which occurred after perivascular manipulation of the artery, an effect consistent with its in vitro proliferation inhibitory activity, suggesting that long-term treatment with SR33805 may reduce or delay SMC proliferation.

Transarterial wall oxygen gradients at the deployment site of an intra-arterial stent in the rabbit

Intimal hyperplasia, common at the deployment site of an intra-arterial stent, may be caused by artery wall hypoxia. The purpose of this study was to determine the effect of an intra-arterial stent on artery wall oxygen concentrations. Transarterial wall oxygen gradients were measured by microelectrode at stent deployment sites in New Zealand White rabbits. Thinned artery walls and decreased oxygen tensions were noted throughout the artery wall immediately following stent deployment with a return toward control values at 28 days. Angioplasty alone had no acute effect on artery wall oxygen concentrations. Larger stent deployment diameters yielded acutely lower artery wall oxygen tensions. Using a linear one-dimensional model for the oxygen profile, we noted that stent deployment resulted in acute changes in oxygen consumption in the inner artery wall that rapidly returned to control values. Changes were noted without differences in blood pressure or arterial blood oxygen concentrations. Oxygen delivery to and consumption within the artery wall are altered by intra-arterial stent deployment. A role for artery wall hypoxia in artery wall pathology at the deployment site of an intra-arterial stent is supported by these findings.

Transarterial wall oxygen gradients at a prosthetic vascular graft to artery anastomosis in the rabbit

PURPOSE

Artery-wall hypoxia has been proposed to contribute to many kinds of artery-wall pathologic conditions, including atherosclerosis and intimal hyperplasia. Intimal hyperplasia is common at sites of arterial injury, including an anastomosis. The purpose of this study was to determine the effect of a prosthetic vascular graft (PVG)-to-artery anastomosis on the delivery of oxygen to the artery wall.

METHODS

The transarterial wall oxygen gradient in the infrarenal aorta of New Zealand White rabbits 2 mm distal to a PVG-to-artery anastomosis was measured with an oxygen microelectrode.

RESULTS

Oxygen tensions were significantly decreased in the outer artery wall immediately after the creation of the anastomosis and showed a further decrease in oxygen tensions at days 7 and 14, which correlated with the absence of a vasa vasorum. After day 14, the oxygen tensions gradually increased, returning to normal by postanastomosis day 42, correlating with a return of the vasa vasorum. These changes were noted without differences in blood pressure or arterial blood oxygen concentrations.

CONCLUSION

The delivery of oxygen to the artery wall is altered by the creation of a PVG-to-artery anastomosis. Low arterial oxygen tensions at a PVG-to-artery anastomosis support a role for artery-wall hypoxia in the formation of intimal hyperplasia at the site of a PVG-to-artery anastomosis.

Association of artery wall hypoxia and cellular proliferation at a vascular anastomosis

BACKGROUND

We hypothesize that arterial wall hypoxia incites the pathologic formation of intimal hyperplasia at an artery anastomosis. We have determined from previous studies performed in our laboratory, the oxygen tension profiles of the artery wall at various times after vascular anastomosis. The purpose of this study is to determine the rate of cellular proliferation at an artery anastomosis when the artery wall is most hypoxic.

MATERIALS AND METHODS

Expanded polytetrafluoroethylene (ePTFE) grafts were placed end to end in the infrarenal aorta of 27 New Zealand white rabbits. The anastomotic aortic wall oxygen (O(2)) tensions were measured with an O(2) microelectrode in rabbits 0, 7, 14, 28, and 42 days after surgery. O(2) tensions were also measured in 4 control rabbits for comparison. 5-Bromo-2'-deoxyuridine (BrDU) was injected intraperitoneally 24 h prior to rabbit sacrifice. After O(2) tension measurements, the rabbits were sacrificed and the aortic grafts were harvested. Bioquant morphometrics was used to measure cells with BrDU counterstaining and intimal thickness in 17 rabbits: in control (n = 4), Day 0 (n = 4), 7 (n = 5), and 42 (n = 4). Student's t test was used to compare O(2) tensions, cellular proliferation, and intimal hyperplasia between days.

RESULTS

The pO(2) levels at the outer layers of the aorta, 1 mm distal to the distal aortic graft anastomosis, were 61.0 +/- 2 (+/-SE) mm Hg for controls, 19.8 +/- 1 mm Hg for Day 7 (P < 0.0001), 19.0 +/- 1 mm Hg for Day 14, 39.2 +/- 1 mm Hg for Day 28, and 58.5 +/- 1 mm Hg for Day 42 aortic grafts. BrDU-staining ratios in the intima were significantly higher in the Day 7 aortic grafts, 28.6 +/- 3%, versus BrDU-staining ratio, 1.4 +/- 1%, in Day 42 aortic grafts (P < 0.0002).

CONCLUSIONS

Cellular proliferation is highest at Day 7 when the artery wall is most hypoxic and returns to baseline as O(2) tensions normalize.

Hypoxia during early developmental period induces long-term changes in the dopamine content and release in a mesencephalic cell culture

The present study was conducted to elucidate the long-term effects of exposure to hypoxia of dopaminergic neurons during the early developmental period. Primary mesencephalic cell cultures prepared from fetal rats and containing 0.5-2% of dopaminergic neurons were exposed to hypoxia between in vitro days 1 and 6, the putative critical developmental period. Changes in the content, release and uptake of dopamine were found to depend on the degree of hypoxia and on the duration of exposure. Following moderate hypoxia (7 h, 5% O2) on two consecutive days between in vitro days 1 and 3, the cultures showed a small increase in the dopamine levels, by 16%. After severe hypoxia (0% O2/95% N2 for 24 h), during the same time window, the cellular dopamine content was elevated by 100%. Moreover, severe hypoxia produced long-lasting modulations of the dopaminergic system. On in vitro day 14, cells exhibited increased levels of 3,4-dihydroxyphenylacetic acid and homovanillic acid (by 34% and 55%, respectively), and elevations of both the spontaneous and potassium-stimulated dopamine release by 70%. The dopamine transport and metabolism of cells exposed to hypoxia between in vitro days 4 and 6 remained unchanged with regard to long-term effects. The present study provides strong evidence for the induction of long-term changes in dopaminergic cells due to hypoxia during the critical developmental period in mesencephalic culture. The developmental period capable of inducing long-lasting changes in dopamine metabolism is restricted to in vitro days 1-3.

Distinct effect of hypoxia on endothelial cell proliferation and cycling

Endothelial cells (EC) occupy a strategic location in the vasculature as a barrier between the intravascular compartment and underlying tissues; as such, they are often exposed to stresses, such as decreases in ambient oxygen, diminished metabolic substrate, or changes in temperature, that could affect their ability to divide and proliferate. The present study characterizes cell counts, cell cycle distribution, and bromodeoxyuridine incorporation in pulmonary artery and aortic EC exposed to acute and/or chronic hypoxia and other cellular stresses. During hypoxia, EC division slows but does not arrest; progression through the G1-to-S transition point and/or progression from S to G2/M is altered with an increased percent of EC in S phase. These changes in EC cell cycle distribution with hypoxia are dependent on the origin of the EC as well as the ambient oxygen concentration; moreover, they are distinct from changes observed with elevated temperature or glucose deprivation. and differ from the quiescent pattern induced by serum deprivation or high-density confluence. These findings demonstrate that hypoxia exerts a distinct effect on the cell cycle distribution and proliferation of EC.

HSP synthesis of neonatal rat heart myocytes is regulated by a collagen environment

Studies on the stress response of isolated myocytes have gained great importance in the understanding of the response of the heart as an organ after, for instance, ischemia. However, the possible role of the extracellular matrix on these effects has thereby been neglected. The recently developed model system of neonatal heart cells cultured on a collagen gel, characterized by a high coherence of contractions, has been used to study the effects of this more in vivo-like collagen environment on the heat shock response of the myocytes as compared to 'normally used' monolayer cultures. After four days differences were found in the heat-induced synthesis of HSPs of cells grown by the two culturing procedures. The degree of induction of different HSPs appeared to be directly related to the basic level of synthesis of these HSPs under the used culturing conditions. In collagen gel-grown cultures the basic level of synthesis as well as the heat-induced synthesis of HSP84 and HSP100 was decreased, for HSP60 both were increased, and for HSP70 no differences were found compared to the monolayer cultures. Our results suggests that the collagen matrix has a regulatory role in the synthesis of HSPs.

The influence of the adventitia on the presence of smooth muscle cells and macrophages in the arterial intima

OBJECTIVE

To test the hypothesis that atherosclerosis may be initiated by hypoperfusion or thrombotic occlusion of the adventitial vasa vasonum.

DESIGN

In a new model of atherogenesis, an early atherosclerotic lesion may be initiated by removal of the adventitia from the carotid artery of the New Zealand White rabbit, wherein lie the vasa vasorum.

SETTING

Animal laboratory, University Department of Surgery and Medicine.

CHIEF OUTCOME MEASURES

Immunocytochemistry was undertaken to demonstrate the presence of smooth muscle cells and macrophages within the intimal lesions. Smooth muscle cells were labelled with a monoclonal antibody designated HHF35 and macrophages were labelled with a rabbit specific, macrophage specific antibody, RAM11. CHIEF RESULTS: In rabbits fed a normal diet, at day 14, the intimal lesion was composed exclusively of smooth muscle cells. By day 28, such lesions had regressed. In rabbits fed a high cholesterol diet, at day 14, the intimal lesion was composed of a mixture of macrophages and smooth muscle cells. By day 42, the pattern of cellular distribution was such that macrophages (present as foam cells) were predominant. In the presence of persistent hypercholesterolaemia these lesions did not regress.

CONCLUSIONS

This new model can produce two different cellular responses that may mimic the intimal lesions seen with re-stenosis after angioplasty or in hypercholesterolaemic man and as such, might be useful in separating out these two different pathophysiologies.

Effect of noise stress and ethanol intake on hearts of spontaneously hypertensive rats

The pathogenesis and progression of hypertensive heart disease are unclear; however, both involve a genetic predisposition and environmental influences. To test the role of exogenous factors, we examined the hearts of spontaneously hypertensive rats (SHR) exposed to noise stress and ethanol intake. Twenty-two SHR and nine normotensive Wistar rats (NWR) were continuously exposed to a 65 db, 4 and 250 Hz tone for 52 weeks. Twelve of these SHR aged 20-22 weeks were concomitantly given 20% ethanol in their drinking water up to week 52. Eight SHR and 12 NWR served as controls. We examined hemodynamic parameters, the cardiac configuration, the cardiac microvasculature, interstitial tissue, and ischemic myocardial lesions. We found that noise stress significantly increased the microvessel wall area, the number of microvessels with an outer diameter > 19 microns, the degree of cardiac fibrosis, and the extent of ischemic myocardial lesions in SHR, but not in NWR. These effects were all ameliorated and the diastolic blood pressure was lowered by the ingestion of ethanol. Cardiac weights and dimensions, heart rate and dp/dtmax were not influenced by either noise or ethanol intake. These results suggest that hypertensive heart disease in SHR can be aggravated by noise stress. Ethanol ameliorates these changes by mechanisms which remain to be explored.

Chronic hypoxia impairs the differentiation of 3T3-L1 fibroblast in culture: role of sustained protein kinase C activation

The effect of hypoxia on 3T3-L1 cell differentiation was examined in confluent cultures incubated with differentiation medium (DM) followed by incubation in growth medium (GM). Control cultures remained in GM throughout the incubation period. Eight days after the incubation, cells were assessed either for changes in morphology by staining with Oil Red O/hematoxylin or harvested to measure protein kinase C activity. Morphological examination of stained cells showed almost complete differentiation of normoxic cells to adipocytes when exposed to DM. By contrast hypoxia caused a dramatic inhibition of differentiation under similar media conditions with only 34 +/- 4% of cells accumulating fat deposits. Cultures sustained in GM under normoxic or hypoxic conditions were devoid of any fat deposits, reflecting an undifferentiated phenotype. Normoxic cells exposed to DM exhibited a significantly lower membrane to cytosolic ratio of protein kinase C in comparison with cells maintained in GM, which is consistent with differentiated and undifferentiated phenotypes, respectively. In comparison with normoxic cells incubated in DM, cells exposed to hypoxia under similar media conditions exhibited a significantly higher membrane to cytosolic ratio of protein kinase C, indicating sustained activation of the enzyme. In addition, cells in differentiation medium exposed to hypoxia in the presence of the protein kinase C inhibitors staurosporine or H7 exhibited a significant increase in the number of fat accumulating cells when compared with hypoxic controls. These studies indicate that chronic hypoxia impairs the differentiation of 3T3-L1 cells to adipocytes in association with the sustained activation of protein kinase C, which appears to play a role in mediating this process.

Regulation by hypoxia of endothelin-1-stimulated phospholipase D activity in sheep pulmonary artery cultured smooth muscle cells

1. The aim of the study was to characterize the effects of hypoxia on agonist-stimulated phospholipase D (PLD) and phospholipase C activity of sheep pulmonary artery cultured smooth muscle cells. 2. Endothelin-1 (ET-1), 5-hydroxytryptamine (5-HT) and the protein kinase C (PKC) activator tetradecanoylphorbol acetate (TPA), stimulated a time- and concentration-dependent increase in [3H]-phosphatidylbutanol accumulation. This was abolished by pretreatment of the cells with the PKC inhibitor, Ro-318220, suggesting that agonist-stimulated phospholipase D activity is dependent upon the activation of PKC. 3. Hypoxia (PO2 20 mmHg for 30 min) stimulated basal [3H]-phosphatidylbutanol accumulation by approximately 2 fold and this activity was abolished by preincubation of the cells with 10 microM Ro-318220. 4. In cells preincubated in low O2 containing medium for 30 min, the subsequent agonist-stimulated accumulation of [3H]-phosphatidylbutanol was reduced. However, the decrease in stimulation was greater for ET-1 and 5-HT than for TPA. 5. ET-1 and TPA stimulated a time-dependent increase in protein kinase C- mediated psuedosubstrate phosphorylation. Following preincubation for 30 min in low O2 containing media, basal pseudosubstrate phosphorylation increased whilst the fold stimulation by TPA and ET-1 decreased. 6. In cells preincubated in low O2 containing medium, ET-1-stimulated [3H]-inositol phosphate accumulation was reduced by approximately 30-40%. This reduction was reversed by preincubation of the cells with Ro-318220. 7. These results suggest a role for PKC in the effects of hypoxia on PLD in pulmonary artery smooth muscle cells.

Development of acquired arteriovenous fistulas in rats due to venous hypertension

Dural sinus thrombosis has been hypothesized as a possible cause of dural arteriovenous fistulas (AVF's). The pathogenesis and evolution from thrombosis to actual development of an AVF are still unknown. To study dural fistula formation, a surgically induced venous hypertension model in rats was created by producing an arteriovenous shunt between the carotid artery and the external jugular vein. The external jugular vein beyond the anastomosis was ligated 2 to 3 months after surgery and angiography was performed to identify any new acquired AVF's. Forty-six male Sprague-Dawley rats, each weighing approximately 300 gm, were used for this study. In Group I, 22 rats underwent a common carotid artery anastomosis to the external jugular vein, which is the largest draining vein from the transverse sinus via the posterior facial vein, followed by proximal external jugular vein ligation. In Group II, 13 rats underwent the same surgical procedure, followed by contralateral posterior facial vein occlusion. Group III served as the control group, in which 11 rats underwent only unilateral external jugular vein occlusion with or without contralateral posterior facial vein occlusion. The shunts in Groups I and II were ligated at 2 to 3 months following surgery, and transfemoral angiography was performed immediately before and after occlusion. New acquired AVF's had developed in three rats (13.6%) in Group I, three rats (23.1%) in Group II, and no rats (0%) in Group III. One of these newly formed fistulas was located at the dural sinus, analogous to the human dural AVF. The other five were located in the subcutaneous tissue, including the face and neck. The dural AVF in the rat was present on follow-up angiography at 1 week after the bypass occlusion. It is concluded that chronic venous hypertension of 2 to 3 months' duration, without associated venous or sinus thrombosis, can induce new AVF's affecting the dural sinuses or the subcutaneous tissue.

The adventitia and atherogenesis: removal initiates intimal proliferation in the rabbit which regresses on generation of a 'neoadventitia'

Removal of the carotid artery adventitia from rabbits induced the formation of an intimal hyperplastic lesion. In rabbits fed a normal diet, the lesion (measured as the intimal:medial ratio) was maximal by day 14 (0.456 +/- 0.079, n = 5, P < 0.01) and thereafter, regressed towards control dimensions (0.037 +/- 0.003, n = 14) by day 28 (0.080 +/- 0.025, n = 7, P = 0.14). In rabbits fed a high cholesterol diet, the lesion was again maximal by day 14 (0.376 +/- 0.056, n = 8, P < 0.01). Although some regression was seen, the lesion persisted to day 42 (0.272 +/- 0.052, n = 8, P < 0.01). Electron microscopy and immunocytochemistry showed two types of lesion, (a) smooth muscle cell predominant on normal diet and, (b) macrophage predominant on high cholesterol diet. Smooth muscle cell predominant lesions underwent almost complete regression, whereas macrophage predominant lesions persisted. We propose that lesion formation may be initiated following the development of arterial wall hypoxia, secondary to excision of the adventitial vasa vasorum. Furthermore, we have devised a novel method to restore a highly vascular 'neoadventitia' to an artery whose adventitia has previously been removed, using loosely placed PVC tubing. We suggest this 'neoadventitia' was able to inhibit the formation of an intimal hyperplastic lesion and to promote regression of an already established lesion by restoring arterial wall oxygenation.

Anoxia, wound healing, VL30 elements, and the molecular basis of malignant conversion

Although VL30 retrotransposable elements have been associated with certain cancers for nearly twenty years, because of their expression in rodent malignancies and recombination into murine sarcoma viruses, their causative role, if any, in cancer has been uncertain and enigmatic. Recent findings suggest loss of normal transcriptional control of specific VL30 element expression may make a critical contribution to tumor progression at a step associated with malignant conversion, by bringing into play a cellular program normally involved in wound healing. This program, the fibroblast anoxic response system, includes an adaptation to glycolytic metabolism, secretion of metalloproteinases, and activation of an endonuclease. While appropriate for facilitating debris removal during wound healing, loss of control of this program in a cell which has already progressed to the benign neoplastic state has the potential to simultaneously produce the invasiveness and genomic instability characteristic of malignancy. Examination of tumors and tumor derived cell lines has confirmed that key aspects of this system are in fact activated in cancer.

Arterial intimal hyperplasia after occlusion of the adventitial vasa vasorum in the pig

Oxygenation of the arterial wall is provided by diffusion of oxygen outward from the main vessel lumen and inward from the adventitial vasa vasorum. In a group of four Yucatan miniature pigs the oxygenation profiles across the superficial femoral arteries were recorded by polarographic oxygen microelectrodes. The profiles obtained suggested a relatively poorly oxygenated media (a trough value of approximately 25% that of the intimal oxygenation) with a progressive rise in oxygenation toward the intimal and adventitial surfaces. In four other survival experiments, occlusion of the adventitial vasa vasorum by flush ligation of the arterial branches that supply them resulted in the production of a focal, intimal hyperplastic lesion that was absent in control vessels (intimal to medial ratios [mean +/- SEM] of 0.053 +/- 0.008, n = 8, p < 0.001 and 0.013 +/- 0.001, n = 8, respectively). By electron microscopy this lesion was seen to be composed mainly of smooth muscle cells. This evidence would support the hypothesis that arterial wall hypoxia may be involved in the initiation of intimal hyperplasia. It is proposed that human atherosclerosis may be initiated by occlusion of the vasa vasorum and concomitant hypoxia.