Celecoxib prevents tumor growth in vivo without toxicity to normal gut: lack of correlation between in vitro and in vivo models

Nonsteroidal anti-inflammatory drugs have potential for use in the prevention and/or treatment of colorectal cancer. We have studied the cytotoxic effect of a specific COX-2 inhibitor, celecoxib, against LLC, HCA-7, and HCT-15 cells grown in cell culture and have compared these results with its effect on HCA-7 cells grown as xenografts in nude mice. "High-dose" celecoxib (>20 microM) reduced the viability of all three cell lines in vitro as measured by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Flow cytometric analysis demonstrated that this loss of viability was attributable to the induction of apoptosis. Significantly, concentrations of the drug <10 microM had no effect on cell viability in vitro. The cytotoxic effects of high-dose celecoxib were independent of COX-2 inhibition because similar effects were observed in cox-2 (+/+), cox-2 (+/-) and cox-2 (-/-) fibroblasts. A plasma concentration of 2.3+/-0.7 microM was achieved when celecoxib (1250 mg/kg of chow) was fed to animals ad libitum. Despite a lack of toxicity at 2-3 microM celecoxib in vitro, there was attenuation of HCA-7 xenograft growth in vivo. Celecoxib had no effect on apoptosis, cell division, or the epithelial architecture of the normal gut in treated mice. These results support the need for additional clinical evaluation of celecoxib for treatment and/or prevention of colorectal cancer in humans.

Posttranscriptional regulation of cyclooxygenase-2 in rat intestinal epithelial cells

Modulation of cyclooxygenase-2 (COX-2) mRNA stability plays an important role in the regulation of its expression by oncogenic Ras. Here, we evaluate COX-2 mRNA stability in response to treatment with two known endogenous promoters of gastrointestinal cancer, the bile acid (chenodeoxycholate; CD) and ceramide. Treatment with CD and ceramide resulted in a 10-fold increase in the level of COX-2 protein and a four-fold lengthening of the half-life of COX-2 mRNA. COX-2 mRNA stability was assessed by Northern blot analysis and by evaluating the AU-rich element located in the COX-2 3'-UTR. A known inhibitor of mitogen-activated protein (MAP)/extracellular signal-regulated kinase (ERK) kinase (MEK), PD98059, reversed the effects of CD or ceramide to stabilize COX-2 mRNA. Overexpression of a dominant-negative ERK-1 or ERK-2 protein also led to destabilization of COX-2 mRNA. Treatment with a p38 MAPK inhibitor, PD169316, or transfection with a dominant-negative p38 MAPK construct reversed the effect of CD or ceramide to stabilize COX-2 mRNA. Expression of a dominant-negative c-Jun N-terminal kinase (JNK) had no effect on COX-2 mRNA stability in cells treated with CD or ceramide. We conclude that posttranscriptional mechanisms play an important role in the regulation of COX-2 expression during carcinogenesis.

Regulation of constitutive cyclooxygenase-2 expression in colon carcinoma cells

Cyclooxygenase-2 (COX-2) is not normally expressed in the human large intestine, but its levels are increased in the majority of human colorectal carcinomas. Here we investigate the regulation of constitutive COX-2 expression and prostaglandin production in human colorectal carcinoma cells. Both COX-2 mRNA and protein were expressed in well differentiated HCA-7, Moser, LS-174, and HT-29 cells, albeit at different levels. COX-2 expression was not detected in several poorly differentiated colon cancer cell lines including DLD-1. Transcriptional regulation played a key role for the expression of COX-2 in human colon carcinoma cells, and both the nuclear factor for interleukin-6 regulatory element and the cAMP-response element were responsible for regulation of COX-2 transcription. COX-2 mRNA was more stable in HCA-7 cells than in the other cell lines tested. Both transcriptional and post-transcriptional regulation of COX-2 involved the MAP kinase pathway. Modulation of the Akt/protein kinase B or Rho B signaling pathways altered the levels of COX-2 expression. Furthermore, COX-2 protein is degraded through ubiquitin proteolysis, and its half-life was approximately 3.5-8 h. HCA-7 cells produced significant quantities of prostaglandin E(2) and other prostaglandins. Moser and LS-174 cells also generated prostaglandins, but levels were significantly lower than that observed in HCA-7 cells.

[Alteration of banked blood cholinesterase level and its significance in emergency treatment of acute organophosphorus pesticide poisoning]

OBJECTIVE

To observe the relationship between the preservation days of banked blood and the alteration level of plasma cholinesterase with the aim of making proper selection of banked blood in emergency treatment of acute organophosphorus pesticide poisoning (AOPP).

METHODS

We selected at random the banked blood that has been stored for different length of time before blood transfusion so as to determine the plasma cholinesterase value. The normal plasma cholinesterase value was determined on blood samples in the Blood Center which served as a control group. The cholinesterase value was determined with a kit of the BM Company and the Cobes-Fara II automatic analysor of the Roch Company.

RESULTS

It was found that there was no significant difference of plasma cholinesterase value between the one-day banked blood and the normal control group (P > 0.05), but the plasma cholinesterase values of the other experiment groups were all significantly lower than that of the control group (P < 0.05). As compared with the normal control group, the relative ratio with fixed base was about from 80 percent to 16 percent. It seems that the preservation days are in negative correlation with the cholinesterase value (r = -0.7929, P < 0.01). The curvilinear regression equation is Y = -1,823.3 Ln(X) +/- 6,229.4.

CONCLUSION

With the increase of the banked blood preservation days after blood sampling, the plasma cholinesterase value decreased gradually. So in the emergency treatment of severe AOPP, it is essential to use the fresh blood collected within one day, so as to avoid missing the chance of first-aid treatment. This study provides the experimental basis for emphasizing transfusion of fresh blood and ensuring transfusion of highly active cholinesterase in treating AOPP.

Periischemic cerebral blood flow (CBF) does not explain beneficial effects of isoflurane on outcome from near-complete forebrain ischemia in rats

BACKGROUND

Isoflurane improves outcome from near-complete forebrain ischemia in rats compared with fentanyl-nitrous oxide (N2O). Sympathetic ganglionic blockade with trimethaphan abolishes this beneficial effect. To evaluate whether anesthesia-related differences in cerebral blood flow (CBF) may explain these findings, this study compared regional CBF before, during, and after near-complete forebrain ischemia in rats anesthetized with either isoflurane (with and without trimethaphan) or fentanyl-nitrous oxide.

METHODS

Fasted, normothermic isoflurane anesthetized Sprague-Dawley rats were prepared for near-complete forebrain ischemia (10 min of bilateral carotid occlusion and mean arterial pressure = 30 mmHg). After surgery, rats were anesthetized with either 1.4% isoflurane (with or without 2.5 mg of trimethaphan intravenously at onset of ischemia) or fentanyl-nitrous oxide (25 microgram. kg-1. h-1. 70% N2O-1). Regional CBF was determined (14C-iodoantipyrine autoradiography) before ischemia, 8 min after onset of ischemia, and 30 min after onset of reperfusion.

RESULTS

Regional CBF did not differ significantly among groups at any measurement interval. Ischemia caused a marked flow reduction to 5% or less of baseline (P < 0.001) in selectively vulnerable regions, such as the cortex, caudoputamen and hippocampus, whereas flow in the brain stem and cerebellum was preserved. Reperfusion at 30 min was associated with partial restoration of flow to 35-50% of baseline values in ischemic structures.

CONCLUSIONS

The results indicate that improved histologic-behavioral outcome provided by isoflurane anesthesia cannot be explained by differential vasodilative effects of the anesthetic states before, during, or after severe forebrain ischemia. This study also shows severe postischemic delayed hypoperfusion that was not affected by choice of anesthetic or the presence of trimethaphan. Mechanisms other than effects on periischemic CBF must be responsible for beneficial effects of isoflurane in this model.

Oncogenic Ras-mediated cell growth arrest and apoptosis are associated with increased ubiquitin-dependent cyclin D1 degradation

The cellular responses to activated Ras vary depending on cell type. Normal cells are often induced into pathways that lead to cell growth arrest, senescence, and/or apoptosis in response to activated Ras expression. These are important protective anti-tumorigenic responses that restrict the propagation of cells bearing activated oncogenes. Here we show that induction of Ha-Ras(Val-12) in Rat-1 fibroblasts resulted in G(1) growth arrest and apoptosis with loss of viable cells that is accompanied by a marked decrease in cyclin D1 levels via increased ubiquitin-proteasome-dependent cyclin D1 turnover. This is in contrast with a rat intestinal epithelial cell line in which induction of Ha-Ras(Val-12) results in transformation associated with sustained proliferation and increased levels of cyclin D1, that is not accompanied by anoikis or apoptosis. Expression of the cyclin D1 mutant (T286A) that contains an alanine for threonine 286 substitution and is resistant to ubiquitin-proteasome degradation in the Ha-Ras(Val-12) expressing Rat-1 cells resulted in a sustained transformed phenotype with no accumulation of cells in G(1). Inhibition of mitogen-activated protein kinase (MEK1/2) pathway partially reversed the Ras-mediated decrease in cyclin D1. Induction of Ha-Ras(Val-12) resulted in activation of Akt kinase and inactivation of glycogen-synthase-3beta kinase that are associated with reduction of cyclin D1 protein. These results suggest that Ras-mediated cyclin D1 degradation in Rat-1 cells appears to be partially dependent on activation of mitogen-activated protein kinase pathway and independent of glycogen-synthase-3beta kinase pathway.

A comparison of strain-related susceptibility in two murine recovery models of global cerebral ischemia

Genetically engineered mice are increasingly important in stroke research. The strains on which these constructs are built are known to have inherent differential sensitivities to ischemic insults. This has been largely attributed to differences in vascular anatomy. This study compared the outcome from forebrain ischemia in two common murine background strains using two different types of ischemic insult. C57Bl/6 and SV129 mice were subjected to two vessel (bilateral carotid) occlusion (2VO) or 2VO plus systemic hypotension (2VO+Hypo; mean arterial pressure=30+/-2 mmHg) for 10-20 min. Ventilation and pericranial temperature were controlled. Cerebral blood flow (CBF) was determined by 14C-iodoantipyrine autoradiography. Histologic damage in forebrain structures was measured 3 days post-ischemia. During 2VO+Hypo, the EEG became isoelectric in all animals. During 2VO alone, EEG isoelectricity occurred in 73% of C57Bl/6 and 50% of SV129 mice. Forebrain CBF was reduced to a similar extent in both strains. Greater CBF variability was seen with 2VO alone versus 2VO+Hypo. CBF was less in the 2VO+Hypo model. SV129 mice had wider posterior communicating but smaller basilar artery diameters. With or without hypotension, SV129 mice had markedly less severe histologic damage than C57Bl/6 mice. A time-dependent increase in histologic damage was demonstrated in the 2VO+Hypo model but not with 2VO alone. The 2VO and 2VO+Hypo models produced similar magnitudes of histologic injury in C57Bl/6 mice subjected to 10-min ischemia. SV129 mice were resistant to ischemia in either model. The 2VO+Hypo model produced a more uniform severity of ischemia as defined by CBF and EEG examination. Despite this, the murine strain had a substantially greater impact on histologic outcome than did cerebrovascular anatomy or the type of model used to produce the ischemic insult.

Prognostic value of vascular endothelial growth factor expression in primary lung carcinoma

To investigate whether an association exists between vascular endothelial growth factor (VEGF) expression and tumor prognosis in primary lung carcinoma, we used immunohistochemical techniques to analyze microvessel density and VEGF expression in lung carcinoma tissue from 98 patients. Tissue had been fresh-frozen at the time of operation and preserved for more than 5 years. The results indicated that VEGF expression was positive for 50 of the 98 patients (51.0%), with 27 (27.6%) being weakly positive and 23 (23.5%) being strongly positive. The microvessel density in tissue showing weakly positive and strongly positive VEGF expression was significantly higher than that in VEGF-negative tumor tissue (P < 0.05: negative vs. weakly positive, P < 0.01: negative vs. strongly positive), we showed demonstrating that VEGF expression was significantly associated with intratumoral microvessel density. The 5-year survival rates were 8.7% for strongly VEGF-positive patients, 43.9% for weakly VEGF-positive patients and 79.2% for VEGF-negative patients, respectively (P < 0.01: negative vs. weakly positive or strongly positive). Furthermore, multivariate analysis employing multiple regression analysis indicated that VEGF expression correlates highly with the overall survival rates of patients with primary lung carcinoma. Two variables, N status and VEGF expression, were found to be significant prognostic factors (P < 0.01). The results of this study suggest that VEGF expression is associated with intratumoral microvessel density. VEGF expression may constitute important independent prognostic evidence that can help us in predicting the outcomes of patients with primary lung carcinomas.

Mice overexpressing extracellular superoxide dismutase have increased resistance to global cerebral ischemia

Transgenic mice, which exhibit a fivefold increase in brain parenchymal extracellular superoxide dismutase (EC-SOD) activity, were used to investigate the role of EC-SOD in global ischemic brain injury. Halothane-anesthetized normothermic wild-type (n = 22) and transgenic (n = 20) mice underwent 10 min of near-complete forebrain ischemia induced by bilateral carotid artery occlusion and systemic hypotension (mean arterial pressure = 30 mm Hg). After 3 days of recovery, the brains were histologically examined. Other mice underwent autoradiographic determination of regional CBF 10 min prior to, during, and 30 min after forebrain ischemia. Histologic injury in the cortex and caudoputamen was minimal in both groups. The percentage of dead hippocampal CA1 neurons was reduced in the EC-SOD transgenic group (wild type = 44 +/- 28%; EC-SOD transgenic = 23 +/- 21%, mean +/- SD, P = 0.015). CBF was similar between groups prior to ischemia. The intraischemic blood flow was severely reduced in forebrain structures and was similar between groups. Blood flow at 30 min postischemia had recovered to 50-60% of baseline values in both groups. These results indicate that EC-SOD can play an important role in defining the magnitude of selective neuronal necrosis resulting from near-complete forebrain ischemia. This implicates involvement of extracellular superoxide anions in the pathologic response to global cerebral ischemia.

Transforming growth factor-beta1 enhances Ha-ras-induced expression of cyclooxygenase-2 in intestinal epithelial cells via stabilization of mRNA

Oncogenic ras induces the expression of cyclooxygenase-2 (COX-2) in a variety of cells. Here we investigated the role of transforming growth factor-beta (TGF-beta) in the Ras-mediated induction of COX-2 in intestinal epithelial cells (RIE-1). RIE-1 cells were transfected with an inducible Ha-Ras(Val12) cDNA and are referred as RIE-iRas cells. the addition of 5 mM isopropyl-1-thio-beta-D-galactopyranoside (IPTG) induced the expression of Ha-Ras(Val12), closely followed by an increase in the expression of COX-2. Neutralizing anti-TGF-beta antibody partially blocked the Ras-induced increase in COX-2. Combined treatment with IPTG and TGF-beta1 resulted in a 20-50-fold increase in the levels of COX-2 mRNA. The t1/2 of COX-2 mRNA was increased from 13 to 24 min by Ha-Ras induction alone. The addition of TGF-beta1 further stabilized the COX-2 mRNA (t1/2 > 50 min). Stable transfection of a luciferase reporter construct containing the COX-2 3'-untranslated region (3'-UTR) revealed that TGF-beta1 treatment and Ras induction each stabilized the COX-2 3'-UTR. Combined treatment with IPTG and TGF-beta1 synergistically increased the luciferase activity. Furthermore, a conserved AU-rich region located in the proximal COX-2 3'-UTR is required for maximal stabilization of COX-2 3'-UTR by Ras or TGF-beta1 and is necessary for the synergistic stabilization of COX-2 3'-UTR by oncogenic Ras and TGF-beta1.

Hair loss in psychopharmacology

Medication-induced alopecia is an occasional side effect of many psychopharmaceuticals. Most of the mood stabilizer and antidepressant drugs can lead to this condition. Some antipsychotic and antianxiety agents induce alopecia. Hair loss is also related to hypothyroidism, which can be induced by lithium and other agents. Alopecia might not be reported by some people, but physicians should be aware of this potential problem which may contribute to noncompliance. Lithium causes hair loss in 12-19% of long-term users. Valproic acid and/ or divalproex precipitates alopecia in up to 12% of patients in a dose-dependent relationship. Incidences up to 28% are observed with high valproate concentration exposures. These pharmaceuticals also can change hair color and structure. The occurrence of carbamazepine-induced alopecia is at or below 6%. Hair loss is less common with other mood stabilizers. Tricyclic antidepressants, maprotilene, trazodone, and virtually all the new generation of antidepressants may on rare occasions lead to alopecia. The same applies to haloperidol, olanzepine, risperidone, clonazepam, and buspirone, but not to other neuroleptics, benzodiazepines, or barbiturates, selected antihistamines, and antiparkinsonians. Discontinuation of the medication or dose reduction almost always leads to complete hair regrowth. The therapeutic value of mineral supplements remains unclear.

First Report of Leaf Blight Caused by Pseudomonas syringae on Cornus mas

Cornellian cherry (Cornus mas) is an enduring dogwood that is primarily grown as an ornamental plant in North America, but in parts of Europe, its fruit is eaten fresh or pickled or made into soft drinks, wine, and liqueur. Cornellian cherry has demonstrated longevity and adaptability and has had no previous disease or pest problems. In Tennessee, a leaf blight was first observed during spring 1996 in nursery plants imported from Europe. The disease quickly spread to other C. mas plants within the nursery and has caused severe damage for three consecutive years. The disease affected mostly leaves and young shoots, causing dark brown necrotic lesions and some die back. In early stages, leaf infection consisted of discrete lesions, angular in shape and surrounded by a chlorotic halo. These lesions eventually coalesced to form large dark necrotic patches that covered a large portion of the leaf or the entire leaf. Disease symptoms were restricted to early spring during wet and cool weather; later in the season new growth was free of symptoms. A bacterium was isolated from infected plants and tested for pathogenicity on C. mas 'Redstone' and C. florida. Symptoms were reproduced on C. mas but not on C. florida. The bacterium was reisolated from inoculated plants, was characterized as gram-negative and rod-shaped, and produced fluorescent pigment on King's medium B agar. The bacterium had a positive reaction to the Levan test and negative reactions to potato rot and arginine dihydrolase tests and was identified as Pseudomonas syringae (1). Samples of the bacterium were sent to Texas A&M University, College Station, for fatty acid analysis, and the results confirmed the identity of P. syringae. P. syringae has caused severe damage in C. florida in the northwestern United States (2); however, this is the first report of P. syringae on C. mas. References: (1) N. W. Schaad, ed. 1988. Laboratory Guide for Identification of Plant Pathogenic Bacteria. The American Phytopathological Society, St. Paul, MN. (2) W. A. Sinclair et. al. 1987. Diseases of Trees and Shrubs. Cornell University Press, Ithaca, NY.

Synergistic induction of cyclooxygenase-2 by transforming growth factor-beta1 and epidermal growth factor inhibits apoptosis in epithelial cells

Increased expression of cyclooxygenase-2 (COX-2) expression has been observed in several human tumor types and in selected animal and cell culture models of carcinogenesis, including lung cancer. Increased expression of COX-2 and production of prostaglandins appear to provide a survival advantage to transformed cells through the inhibition of apoptosis, increased attachment to extracellular matrix, increased invasiveness, and the stimulation of angiogenesis. In the present studies, we found that transforming growth factor beta1 (TGF-beta1) and epidermal growth factor (EGF) synergistically induced the expression of COX-2 and prostaglandin E2 (PGE2) production in mink lung epithelial (Mv1Lu) cells. EGF, but not PDGF or IGF-1, was able to inhibit TGF-beta1-induced apoptosis in Mv1Lu cells and this effect was blocked by NS-398, a selective inhibitor of COX-2 activity, suggesting a possible role for COX-2 in the anti-apoptotic effect of EGF receptor ligands. The combination of TGF-beta1 and EGF also significantly induced COX-2 expression in rat intestinal epithelial (RIE-1) cells and completely prevented sodium butyrate (NaBu)-induced apoptosis. The synergistic induction of COX-2 by TGF-beta1 and EGF was not observed in R1B-L17 cells, a line derived from Mv1Lu cells that lacks the TGF-beta type-I receptor. AG1478, a selective inhibitor of EGF receptor tyrosine kinase activity, completely suppressed the induction of COX-2 expression by either EGF or TGF-beta1+EGF. Also, PD98059, a specific inhibitor of MEK/ERK pathway, and SB203580, a specific inhibitor of p38 MAPK activity, significantly inhibited the induction of COX-2 in response to combined EGF and TGF-beta1. These results suggest an important collaborative interaction of TGF-beta1 and EGF signaling in the induction of COX-2 and prostaglandin production in Mv1Lu cells.

LC2, the chlamydomonas homologue of the t complex-encoded protein Tctex2, is essential for outer dynein arm assembly

Tctex2 is thought to be one of the distorter genes of the mouse t haplotype. This complex greatly biases the segregation of the chromosome that carries it such that in heterozygous +/t males, the t haplotype is transmitted to >95% of the offspring, a phenomenon known as transmission ratio distortion. The LC2 outer dynein arm light chain of Chlamydomonas reinhardtii is a homologue of the mouse protein Tctex2. We have identified Chlamydomonas insertional mutants with deletions in the gene encoding LC2 and demonstrate that the LC2 gene is the same as the ODA12 gene, the product of which had not been identified previously. Complete deletion of the LC2/ODA12 gene causes loss of all outer arms and a slow jerky swimming phenotype. Transformation of the deletion mutant with the cloned LC2/ODA12 gene restores the outer arms and rescues the motility phenotype. Therefore, LC2 is required for outer arm assembly. The fact that LC2 is an essential subunit of flagellar outer dynein arms allows us to propose a detailed mechanism whereby transmission ratio distortion is explained by the differential binding of mutant (t haplotype encoded) and wild-type dyneins to the axonemal microtubules of t-bearing or wild-type sperm, with resulting differences in their motility.

[Studies on the infrared and fluorescence spectra of europium lanthanum-benzoate complexes]

A series of mixed rare earth complexes of benzoic acid with europium and lanthanum were synthesized by the reaction of trivalent rare earth chlorides with ammonium benzoate in aqueous solution. Their composition is expressed with the general formula (Eu(1-chi)La(chi)) L3, where L = C6H5COO(-1), chi = 0.0-1.0. Their infrared and fluorescence spectra were investigated. The characteristic asymmetric (v(as)) and symmetric (v(s)) stretching vibrations of carboxyl group for rare earth complexes shift to lower frequency in comparison with sodium benzoate, and both the absorption bands show splitting. In addition, the difference between v(as) and v(s), deltav (120-125) cm(-1), is lees than that of sodium benzoate (deltav =137 cm(-1)). These situations show that the coordinating pattern of the carboxyl groups in the complexes is the form of chelation-bridging, therefore, it may be suggested that the rare earth (Eu, La) benzoates are a heteronuclear polymers. The dependence of the relative fluorescence intensity of the mixed rare earth complexes upon the content for La3+ ions was discussed. The results show that the emission intensity for Eu3+ ions can be greatly enhanced if a part of Eu3+ ions in europium benzoate were substituted by La3+ inos. When chi = 0.4, 0.5 or 0.7, the fluorescence intensity of the rare earth complexes can rise above 40%.

Sulindac sulfide, but not sulindac sulfone, inhibits colorectal cancer growth

Sulindac sulfide, a metabolite of the nonsteroidal antiinflammatory drug (NSAID) sulindac sulfoxide, is effective at reducing tumor burden in both familial adenomatous polyposis patients and in animals with colorectal cancer. Another sulindac sulfoxide metabolite, sulindac sulfone, has been reported to have antitumor properties without inhibiting cyclooxygenase activity. Here we report the effect of sulindac sulfone treatment on the growth of colorectal carcinoma cells. We observed that sulindac sulfide or sulfone treatment of HCA-7 cells led to inhibition of prostaglandin E2 production. Both sulindac sulfide and sulfone inhibited HCA-7 and HCT-116 cell growth in vitro. Sulindac sulfone had no effect on the growth of either HCA-7 or HCT-116 xenografts, whereas the sulfide derivative inhibited HCA-7 growth in vivo. Both sulindac sulfide and sulfone inhibited colon carcinoma cell growth and prostaglandin production in vitro, but sulindac sulfone had no effect on the growth of colon cancer cell xenografts in nude mice.

Extracellular superoxide dismutase deficiency worsens outcome from focal cerebral ischemia in the mouse

The role of endogenous extracellular superoxide dismutase (EC-SOD) was examined in a murine model of transient focal cerebral ischemia. Homozygous EC-SOD deficient (EC-SOD-/-; n = 18) and wild type (EC-SOD+/+; n = 19) littermates were anesthetized with halothane and subjected to 50 min of intraluminal middle cerebral artery occlusion with pericranial temperature maintained at 37.0 degrees C. After 24 h of reperfusion, resultant hemiparesis and cerebral infarct size were measured. Total infarct volume was 81% greater (P = 0.03) and hemiparesis was more severe (P = 0.01) in EC-SOD-/- versus EC-SOD+/+ mice. The worsened ischemic outcome observed in EC-SOD-/- mice is consistent with prior work which found transgenic EC-SOD overexpressing mice to exhibit enhanced tolerance to focal ischemia. The results suggest that endogenous antioxidant activity in the extracellular compartment plays an important role in the histologic/neurologic response to focal cerebral ischemia.

Effects of RSR13, a synthetic allosteric modifier of hemoglobin, alone and in combination with dizocilpine, on outcome from transient focal cerebral ischemia in the rat

This study examined the effect of a pharmacologically induced rightward shift in the partial pressure of oxygen at which 50% of hemoglobin is saturated (P50) on outcome from transient focal cerebral ischemia in the rat. Halothane anesthetized rats (n=20 per group) were given saline or a single 15-min infusion of 150 mg/kg RSR13 (2-[4-[[3,5-dimethylanilino) carbonyl]methyl]phenoxy]-2-methylproprionic acid) intravenously before or 30 min after onset of 75 min of middle cerebral artery filament occlusion (MCAO). Seven days later, severity of hemiparesis and cerebral infarct size were examined. RSR13 alone did not significantly improve outcome. Conscious normothermic rats (n=12 per group) were also given RSR13 (150 mg/kg) or 0.9% NaCl intravenously and subjected to 75 min of MCAO with 7 days of recovery. Again, RSR13 alone did not significantly reduce infarct size or improve neurologic score. A dose-response curve for dizocilpine (MK-801) was then constructed in conscious normothermic rats subjected to 75 min of MCAO. Dizocilpine (0.5 mg/kg i.v.) caused a 90% reduction in mean infarct size while 0.25 mg/kg reduced infarct size by 48%. Other rats were then subjected to 75 min of MCAO after being given dizocilpine (0.25 mg/kg i.v.; n=18) or RSR13 (150 mg/kg i.v. )+dizocilpine (0.25 mg/kg i.v.; n=15). RSR13+dizocilpine resulted in smaller cortical infarct volume (8+/-14 mm3 vs. 34+/-37 mm3, p<0.02) and total cerebral infarct volume (46+/-28 mm3 vs. 81+/-60 mm3, p<0. 05) compared to dizocilpine alone, respectively. We conclude that a pre-ischemic peak increase in P50 of approximately 25 mmHg alone is insufficient to reduce focal ischemic injury, but may be advantageous when used in conjunction with other neuroprotective agents.

Apolipoprotein E deficiency worsens outcome from global cerebral ischemia in the mouse

BACKGROUND AND PURPOSE

Apolipoprotein E (apoE) has been found relevant in a variety of central nervous system disorders. This experiment examined the effect of endogenous murine apoE on selective neuronal necrosis resulting from a transient forebrain ischemia insult.

METHODS

ApoE deficient (n=16) and wild type (n=17) halothane-anesthetized mice were subjected to severe forebrain ischemia (10 minutes of bilateral carotid occlusion and systemic hypotension). After 3 days' recovery, brain injury was determined histologically. In other apoE-deficient and wild-type mice, regional cerebral blood flow (CBF) was determined by 14C-iodoantipyrine autoradiography 10 minutes before, 5 minutes after onset of, and 30 minutes after reperfusion from 10 minutes of forebrain ischemia.

RESULTS

The percentage of dead hippocampal CA1 neurons (mean+/-SD) was greater in the apoE-deficient group (apoE deficient=67+/-30%; wild type=37+/-33%; P=0.011). A similar pattern was observed in the caudoputamen (P=0.002) and neocortex (P=0.014). Cerebral blood flow was similar between groups at each measurement interval. Marked hypoperfusion persisted in both groups at 30 minutes after ischemia.

CONCLUSIONS

ApoE deficiency worsens ischemic outcome. This is not attributable to effects on CBF. A role of apoE in the cerebral response to global ischemia is consistent with prior reports that murine apoE deficiency increases infarct size resulting from focal cerebral ischemia.

Characterization of a recovery global cerebral ischemia model in the mouse

Transgenic/knockout murine variants allow roles of specific proteins to be studied in cerebral ischemia. Because of the size of mice, however, study of prolonged recovery from global ischemia has been limited. This project characterized an adaptation of the rat two-vessel occlusion model of global ischemia for use in the mouse. C57B1/6J mice (8 weeks old; 21 +/- 1 g) were overnight fasted, anesthetized with halothane, intubated and mechanically ventilated. The right internal jugular vein and femoral artery were cannulated. Pericranial temperature was held at 37.0 degrees C. The carotid arteries were occluded and mean arterial pressure was reduced to 35 mmHg with 0.3 mg intra-arterial trimethaphan and venous exsanguination. Electroencephalographic isoelectricity was confirmed in cohort mice. Ten minutes later ischemia was reversed. Mice were allowed 1, 3 or 5 days survival followed by histologic analysis. Regional cerebral blood flow (CBF) was determined autoradiographically. Outcome effects of intra-ischemic hyperglycemia (approximately 350 mg/dl) or hypothermia (34 degrees C) were also examined. The mortality rate was less than 10% in all recovery groups. Ischemia caused reduction of CBF to < 2% of sham values in cortex, hippocampus, and caudoputamen. CBF was unchanged in thalamus, brainstem and cerebellum. CA1 damage, greater after 3 days vs. 1 day reperfusion, was not further increased at 5 days. Histologic injury was increased by hyperglycemia although seizures did not occur. Hypothermia reduced CA1 damage. This study demonstrates feasibility of using the two-vessel occlusion + hypotension recovery model in the mouse. Recovery intervals of > or = 3 days are required to account for delayed CA1 neuronal necrosis. Histologic outcome can be modulated by known physiologic determinants of ischemic brain damage.

Pronounced pharmacologic deficits in M2 muscarinic acetylcholine receptor knockout mice

Members of the muscarinic acetylcholine receptor family (M1-M5) are known to be involved in a great number of important central and peripheral physiological and pathophysiological processes. Because of the overlapping expression patterns of the M1-M5 muscarinic receptor subtypes and the lack of ligands endowed with sufficient subtype selectivity, the precise physiological functions of the individual receptor subtypes remain to be elucidated. To explore the physiological roles of the M2 muscarinic receptor, we have generated mice lacking functional M2 receptors by using targeted mutagenesis in mouse embryonic stem cells. The resulting mutant mice were analyzed in several behavioral and pharmacologic tests. These studies showed that the M2 muscarinic receptor subtype, besides its well documented involvement in the regulation of heart rate, plays a key role in mediating muscarinic receptor-dependent movement and temperature control as well as antinociceptive responses, three of the most prominent central muscarinic effects. These results offer a rational basis for the development of novel muscarinic drugs.

Coordinate regulation of cyclooxygenase-2 and TGF-beta1 in replication error-positive colon cancer and azoxymethane-induced rat colonic tumors

Evidence is accumulating which indicates that cyclooxygenase-2 (COX-2) is involved in the pathogenesis of colorectal cancer. We evaluated the expression of COX-2 in replication error-positive (RER) colon cancers, colon cancers metastatic to liver and azoxymethane (AOM)-induced rat colonic tumors. Immunohistochemistry showed that COX-2 was low to undetectable in normal human mucosa, but abundant in the RER adenocarcinomas we examined. COX-2 immunoreactivity in metastatic colon cancers was less abundant, but clearly detectable. In the colon of AOM-treated rats, COX-2 protein was not detectable in normal mucosa, but present in most of the epithelial cells comprising the tumors. The TGF-beta1 staining pattern in these human and rat tumors was similar to that observed for COX-2. The role of TGF-beta in RER adenocarcinomas is complex because of the increased mutation rate of TGF-beta type II receptors. Northern analysis showed abundant TGF-beta1 mRNA in AOM-induced tumors, but not in paired mucosa. TGF-beta1 induced the expression of COX-2 mRNA and protein in intestinal epithelial cells (IEC-6). Chronic TGF-beta1 treatment caused a TGF-beta-dependent overexpression of COX-2 in rat intestinal epithelial cells (RIE-1). TGF-beta1 may regulate COX-2 expression during the colonic adenoma to carcinoma sequence.

Transformation of intestinal epithelial cells by chronic TGF-beta1 treatment results in downregulation of the type II TGF-beta receptor and induction of cyclooxygenase-2

The precise role of TGF-beta in colorectal carcinogenesis is not clear. The purpose of this study was to determine the phenotypic alterations caused by chronic exposure to TGF-beta in non-transformed intestinal epithelial (RIE-1) cells. Growth of RIE-1 cells was inhibited by >75% following TGF-beta1 treatment for 7 days, after which the cells resumed a normal growth despite the presence of TGF-beta1. These 'TGF-beta-resistant' cells (RIE-Tr) were continuously exposed to TGF-beta for >50 days. Unlike the parental RIE cells, RIE-Tr cells lost contact inhibition, formed foci in culture, grew in soft agarose. RIE-Tr cells demonstrated TGF-beta-dependent invasive potential in an in vitro assay and were resistant to Matrigel and Na-butyrate-induced apoptosis. The RIE-Tr cells were also tumorigenic in nude mice. The transformed phenotype of RIE-Tr cells was associated with a 95% decrease in the level of the type II TGF-beta receptor (TbetaRII) protein, a 40-fold increase in cyclooxygenase-2 (COX-2) protein, and 5.9-fold increase in the production of prostacyclin. Most RIE-Tr subclones that expressed low levels of TbetaRII and high levels of COX-2 were tumorigenic. Those subclones that express abundant TbetaRII and low levels of COX-2 were not tumorigenic in nude mice. A selective COX-2 inhibitor inhibited RIE-Tr cell growth in culture and tumor growth in nude mice. The reduced expression of TbetaRII, increased expression of COX-2, and the ability to form colonies in Matrigel were all reversible upon withdrawal of exogenous TGF-beta1 for the RIE-Tr cells.

Mice overexpressing extracellular superoxide dismutase have increased resistance to focal cerebral ischemia

Transgenic mice, which had been transfected with the human extracellular superoxide dismutase gene, causing an approximate five-fold increase in brain parenchymal extracellular superoxide dismutase activity, were used to investigate the role of extracellular superoxide dismutase in ischemic brain injury. Transgenic (n = 21) and wild-type (n = 19) mice underwent 90 min of intraluminal middle cerebral artery occlusion and 24 h of reperfusion. Severity of resultant hemiparesis and cerebral infarct size were measured. Wild-type mice had larger infarcts (cortex: wild type =37+/-14 mm3, transgenic = 27+/-13 mm3, P=0.03; subcortex: wild type = 33+/-14 mm3, transgenic = 23+/-10 mm3, P = 0.02). Neurological scores, however, were similar (P = 0.29). Other mice underwent autoradiographic determination of intra-ischemic cerebral blood flow. The volume of tissue at risk of infarction (defined as volume of tissue where blood flow was <25 ml/100g/min) was similar between groups (cortex: wild type = 51+/-15 mm3, transgenic = 47+/-9 mm3, P=0.65; subcortex: wild type = 39+/-16 mm3, transgenic= 37+/-17 mm3, P=0.81). These results indicate that antioxidant scavenging of free radicals by extracellular superoxide dismutase plays an important role in the histological response to a focal ischemic brain insult.