Biomedical subjects

Y Mori

Publications and source records attributed to Y Mori.

At least 19 recordsLinked to original sources

PubMed1999

Molecular and functional characterization of a novel mouse transient receptor potential protein homologue TRP7. Ca(2+)-permeable cation channel that is constitutively activated and enhanced by stimulation of G protein-coupled receptor.

Characterization of mammalian homologues of Drosophila transient receptor potential protein (TRP) is an important clue to understand molecular mechanisms underlying Ca(2+) influx activated in response to stimulation of G(q) protein-coupled receptors in vertebrate cells. Here we have isolated cDNA encoding a novel seventh mammalian TRP homologue, TRP7, from mouse brain. TRP7 showed abundant RNA expression in the heart, lung, and eye and moderate expression in the brain, spleen, and testis. TRP7 recombinantly expressed in human embryonic kidney cells exhibited distinctive functional features, compared with other TRP homologues. Basal influx activity accompanied by reduction in Ca(2+) release from internal stores was characteristic of TRP7-expressing cells but was by far less significant in cells expressing TRP3, which is structurally the closest to TRP7 in the TRP family. TRP7 induced Ca(2+) influx in response to ATP receptor stimulation at ATP concentrations lower than those necessary for activation of TRP3 and for Ca(2+) release from the intracellular store, which suggests that the TRP7 channel is activated independently of Ca(2+) release. In fact, TRP7 expression did not affect capacitative Ca(2+) entry induced by thapsigargin, whereas TRP7 greatly potentiated Mn(2+) influx induced by diacylglycerols without involvement of protein kinase C. Nystatin-perforated and conventional whole-cell patch clamp recordings from TRP7-expressing cells demonstrated the constitutively activated and ATP-enhanced inward cation currents, both of which were initially blocked and then subsequently facilitated by extracellular Ca(2+) at a physiological concentration. Impairment of TRP7 currents by internal perfusion of the Ca(2+) chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid revealed an essential role of intracellular Ca(2+) in activation of TRP7, and their potent activation by the diacylglycerol analogue suggests that the TRP7 channel is a new member of diacylglycerol-activated cation channels. Relative permeabilities indicate that TRP7 is slightly selective to divalent cations. Thus, our findings reveal an interesting correspondence of TRP7 to the background and receptor stimulation-induced cation currents in various native systems.

Amino Acid Sequence↗

PubMed1999

Oral administration of lipopolysaccharide exacerbates collagen-induced arthritis in mice.

We investigated whether oral administration of LPS exacerbated collagen-induced arthritis (CIA) in mice, which was an experimental model of autoimmune disease. CIA was induced by s.c. injection of type II collagen emulsified with CFA into the base of the tail (day 0) followed by a booster injection on day 21. To examine the ability of LPS to exacerbate CIA, varying doses of LPS were orally administered on day 50. The results showed that administration of LPS was followed by reactivation of CIA in a dose-related fashion. Histologically, on day 55 there were marked edema of synovium proliferated by day 50, new formation of fibrin, and intense infiltration of neutrophils accompanied with a large number of mononuclear cells. Severe destruction of cartilage and subchondral bone was also observed on day 70. The reactivation of CIA by oral administration of LPS was associated with increase in anti-type II collagen IgG and IgG2a Abs as well as varying kinds of cytokines including IL-12, IFN-gamma, IL-1beta, and TNF-alpha. Polymyxin B sulfate given either orally or i.v. suppressed the recurrence of CIA. Increased amounts of LPS were found in sera of mice given the endotoxin orally. LPS from Salmonella enteritidis, Salmonella typhimurium, and Klebsiella pneumoniae and its component, lipid A from Escherichia coli, also reactivated the disease. These findings suggest that LPS from intestinal bacteria may play a role in the exacerbation of autoimmune joint inflammation.

Administration, Oral↗

PubMed1999

Production of a recombinant chitin deacetylase in the culture medium of Escherichia coli cells.

With the aid of a signal sequence of a chitinase from Streptomyces lividans, a recombinant chitin deacetylase, whose gene originated from a Deuteromycete, Colletotrichum lindemuthianum, was produced in the culture medium of Escherichia coli cells, existing as a highly active form without the signal peptide. During the production of the recombinant chitin deacetylase, both a slight increase in the value of OD600 nm in the culture medium and a drastic decrease in viable cell number were observed. When penta-N-acetyl-chitopentaose was used as the substrate, the recombinant chitin deacetylase had comparable kinetic parameters to those of the original enzyme from the fungus. The addition of a C-terminal six histidine sequence to the recombinant enzyme caused a slight decrease in the kcat value, and the further addition of a 12 amino acid sequence at its N-terminus caused a further decrease in the value. This production system allowed us to easily produce in the culture media the recombinant chitin deacetylases possessing as good properties as the original enzyme, without any disruption steps of the E. coli cells.

Amidohydrolases↗

PubMed1999

The expressed localization of rat putative pheromone receptors.

The localization of pheromone receptors in the rat vomeronasal epithelium was examined by light- and electron-microscopic immunocytochemical analysis, using affinity-purified polyclonal antibodies. The antibodies were raised against a synthetic oligopeptide corresponding to a partial sequence of the rat putative pheromone receptor (VN6). Positive immunoreactivity was observed on the luminal surface of the sensory epithelium, and was abolished when an excess of the antigen peptide was added to the primary reaction solution. On electron microscopy, the immunoreactivity for the VN6 peptide was localized at the dendritic knobs and microvilli of receptor cells, but not in those of the supporting cells. These results show the first evidence of cellular localization of putative pheromone receptors in rat vomeronasal receptor cells.

Animals↗

PubMed1999

Direct suppression of TCR-mediated activation of extracellular signal-regulated kinase by leukocyte protein tyrosine phosphatase, a tyrosine-specific phosphatase.

Leukocyte protein tyrosine phosphatase (LC-PTP)/hemopoietic PTP is a human cytoplasmic PTP that is predominantly expressed in the hemopoietic cells. Recently, it was reported that hemopoietic PTP inhibited TCR-mediated signal transduction. However, the precise mechanism of the inhibition was not identified. Here we report that extracellular signal-regulated kinase (ERK) is the direct target of LC-PTP. LC-PTP dephosphorylated ERK2 in vitro. Expression of wild-type LC-PTP in 293T cells suppressed the phosphorylation of ERK2 by a mutant MEK1, which was constitutively active regardless of upstream activation signals. No suppression of the phosphorylation was observed by LC-PTPCS, a catalytically inactive mutant. In Jurkat cells, LC-PTP suppressed the ERK and p38 mitogen-activated protein kinase cascades. LC-PTP and LC-PTPCS made complexes with ERK1, ERK2, and p38alpha, but not with the gain-of-function sevenmaker ERK2 mutant (D321N). A small deletion (aa 1-46) in the N-terminal portion of LC-PTP or Arg to Ala substitutions at aa 41 and 42 resulted in the loss of ERK binding activity. These LC-PTP mutants revealed little inhibition of the ERK cascade activated by TCR cross-linking. On the other hand, the wild-type LC-PTP did not suppress the phosphorylation of sevenmaker ERK2 mutant. Thus, the complex formation of LC-PTP with ERK is the essential mechanism for the suppression. Taken collectively, these results indicate that LC-PTP suppresses mitogen-activated protein kinase directly in vivo.

Calcium-Calmodulin-Dependent Protein Kinases↗

PubMed1999

Daily fluctuation of 7-alkoxycoumarin O-dealkylase activities in the liver of male F344 rats under ad libitum-feeding or fasting condition.

It has been reported that drug metabolizing enzyme activities in the liver fluctuate daily, though the daily fluctuation of 7-alkoxycoumarin O-dealkylase (ACD) activities catalyzed by P450 has not been examined. The ACD activities are known to be useful to clarify the extensive induction of P450-dependent oxygenases. In the present study, the hepatic ACD activities, as well as P450 content, were investigated periodically in male F344 rats under ad libitum-feeding or fasting condition. The ACD activities in ad libitum-fed rats were found to follow obvious daily fluctuations with high values during dark periods and with low values during light periods. This agreed with the other previous results of drug metabolizing enzyme activities measured with other substrates. Because the daily fluctuation was also observed in fasted rats, the fluctuation in ACD activities was clearly not affected by feeding, an external factor. P450 content, however, showed different fluctuation patterns from the ACD activities. This suggests that the fluctuation of ACD activities might not be related to the quantitative variation of P450 proteins.

7-Alkoxycoumarin O-Dealkylase↗

PubMed1999

Effect of cigarette smoke on the mutagenic activation of environmental carcinogens by rodent liver.

In order to assess the effect of cigarette smoke (CS) on metabolic enzymes, male hamsters and rats were exposed for two weeks to smoke produced in a Hamburg type II smoking machine. The livers were then used for Ames liquid incubation and western immunoblot assays. Mutagenic activities of seven heterocyclic amines (HCAs) in Salmonella typhimurium TA98 in the presence of rat or hamster liver S9 were elevated up to 3.7 times above controls (including sham smoke control). Enhancement of mutagenic activities of PhIP and aflatoxin B(1) was observed only in CS-exposed hamster, whereas no significant alteration of mutagenicity was observed with 2-aminofluorene, benzo[a]pyrene, and 3'-hydroxymethyl-N, N-dimethyl-4-aminoazobenzene in strain TA98 or with six N-nitrosodialkylamines in strain TA100. 7,8-Benzoflavone and/or furafylline considerably inhibited the mutagenic activation of IQ and Trp-P-1 in the presence of liver S9 from untreated hamsters and sham smoke- or CS-exposed hamsters and rats, indicating the predominant involvement of hamster cytochrome P450 (CYP) 1A enzymes in the metabolic activation of HCAs. In addition, the data suggest that CS-exposure may selectively induce hepatic CYP1A1/1A2 isoforms. Western immunoblot analyses of liver microsomes using anti-rat CYP antibodies revealed that CS-exposure increased the levels of hamster CYP1A2 (3.9-fold) and rat CYP1A2 (3.0-fold) and CYP1A1, without significant change in the levels of CYP2E1 and CYP2B and 3A isoforms in each species. The presently observed selective induction of HCA activation and CYP isozymes due to CS supports the idea that CS may contribute to enhancing effects on initiation by carcinogens which are metabolically activated by hepatic CYP1A1/1A2. In conjunction with results observed for smokers, the present findings indicate that the hamster is a good animal for studies with CS, and that cigarette smoking in combination with intake of heating protein-rich foods as a life style may markedly contribute to the human carcinogenesis by HCAs.

Amines↗

PubMed1999

Formation of Nepsilon-(hexanonyl)lysine in protein exposed to lipid hydroperoxide. A plausible marker for lipid hydroperoxide-derived protein modification.

The objectives of this study were to estimate the structure of the lipid hydroperoxide-modified lysine residue and to prove the presence of the adducts in vivo. The reaction of lipid hydroperoxide toward the lysine moiety was investigated employing N-benzoyl-glycyl-L-lysine (Bz-Gly-Lys) as a model compound of Lys residues in protein and 13-hydroperoxyoctadecadienoic acid (13-HPODE) as a model of the lipid hydroperoxides. One of the products, compound X, was isolated from the reaction mixture of 13-HPODE and Bz-Gly-Lys and was then identified as N-benzoyl-glycyl-Nepsilon-(hexanonyl)lysine. To prove the formation of Nepsilon-(hexanonyl)lysine, named HEL, in protein exposed to the lipid hydroperoxide, the antibody to the synthetic hexanonyl protein was prepared and then characterized in detail. Using the anti-HEL antibody, the presence of HEL in the lipid hydroperoxide-modified proteins and oxidized LDL was confirmed. Furthermore, the positive staining by anti-HEL antibody was observed in human atherosclerotic lesions using an immunohistochemical technique. The amide-type adduct may be a useful marker for the lipid hydroperoxide-derived modification of biomolecules.

Humans↗

PubMed1999

Regulation of phosphorylation level and distribution of PTP36, a putative protein tyrosine phosphatase, by cell-substrate adhesion.

Recently we have cloned a putative protein tyrosine phosphatase, PTP36/PTPD2/pez, which possesses a domain homologous to the N-terminal half of band 4.1 protein. In mouse fibroblasts adhered to substrates, PTP36 was phosphorylated on serine residues. PTP36 was found to make complexes with serine/threonine kinase(s), which phosphorylated PTP36 in vitro. PTP36 was dephosphorylated rapidly when the cell-substrate adhesion was disrupted and it was phosphorylated again along with the reattachment of the cells to fibronectin. Rephosphorylation of PTP36 seemed to depend on actin polymerization since it was inhibited by cytochalasin D. The cell detachment also induced the translocation of PTP36 into the membrane-associated cytoskeletal fraction. Staurosporine and ML-9, which inhibited the phosphorylation of PTP36 in vivo, induced the translocation of PTP36 too. On the contrary, when the dephosphorylation of PTP36 was inhibited by okadaic acid, no translocation of PTP36 was induced by the cell detachment. These results demonstrate that the cell-substrate adhesion and cell spreading regulates the intracellular localization of PTP36 most likely through its phosphorylation and therefore, PTP36 may play important roles in the signal transduction pathway of cell-adhesion.

Animals↗

PubMed1999

Isolation and functional characterization of the 5'-upstream region of mouse P/Q-type Ca2+ channel alpha1A subunit gene.

The omega-agatoxin-IVA-sensitive P/Q-type Ca2+ channel is predominantly expressed in the nervous system. To dissect the molecular mechanisms underlying the neuron-specific expression of the P/Q-type channel, we have isolated and characterized the 5'-upstream region of the mouse alpha1A subunit gene. A transcription start site appeared to exist at -269 bp upstream from the start codon as found by 5' RACE analysis. The proximal promoter of the alpha1A subunit gene lacks a typical TATA box, but contains several transcription factor binding sequences, including two Sp1 sites. When linked to a placental alkaline phosphatase (PLAP) reporter gene to examine the promoter activity, the 6.3-kb (-6,273 to +269) 5'-upstream region, but not a smaller 3.0-kb construct (-3, 021 to +269), was able to drive the reporter gene in neuron-like PC12 cells. In contrast, neither of these constructs enhanced the PLAP expression in fibroblast NIH3T3 cells. The sequence between 6.3 and 3.0 kb of the 5'-upstream region did not show promoter activity in either of the cell lines, but enhanced TK promoter activity in PC12 cells, though not in NIH3T3 cells. These results suggest that neuron-specific elements of the alpha1A subunit gene are likely to be located in the distal upstream regions (-6,273 to -3,021) of the 5'-upstream sequence.

3T3 Cells↗

PubMed1999

Auxiliary subunits operate as a molecular switch in determining gating behaviour of the unitary N-type Ca2+ channel current in Xenopus oocytes.

1. We systematically examined the biophysical properties of omega-conotoxin GVIA-sensitive neuronal N-type channels composed of various combinations of the alpha1B, alpha2/delta and beta1b subunits in Xenopus oocytes. 2. Whole-cell recordings demonstrated that coexpression of the beta1b subunit decelerated inactivation, whereas the alpha2/delta accelerated both activation and inactivation, and cancelled the kinetic effects of the beta1b. The alpha2/delta and the beta1b controlled voltage dependence of activation differently: the beta1b significantly shifted the current-voltage relationship towards the hyperpolarizing direction; however, the alpha2/delta shifted the relationship only slightly in the depolarizing direction. The extent of voltage-dependent inactivation was modified solely by the beta1b. 3. Unitary currents measured using a cell-attached patch showed stable patterns of opening that were markedly different among subunit combinations in their kinetic parameters. The alpha2/delta and the beta1b subunits also acted antagonistically in regulating gating patterns of unitary N-type channels. Open time was shortened by the alpha2/delta, while the fraction of long opening was enhanced by the beta1b. The alpha2/delta decreased opening probability (Po), while the beta1b increased Po. alpha1Balpha2/deltabeta1b produced unitary activity with an open time distribution value in between those of alpha1Balpha2/delta and alpha1Bbeta1b. However, both the alpha2/delta and the beta1b subunits reduced the number of null traces. 4. These results suggest that the auxiliary subunits alone and in combination contribute differently in forming gating apparatuses in the N-type channel, raising the possibility that subunit interaction contributes to the generation of functional diversity of N-type channels in native neuronal preparations also.

Animals↗

PubMed1999

Direct alteration of the P/Q-type Ca2+ channel property by polyglutamine expansion in spinocerebellar ataxia 6.

Spinocerebellar ataxia 6 (SCA6) is caused by expansion of a polyglutamine stretch, encoded by a CAG trinucleotide repeat, in the human P/Q-type Ca(2+) channel alpha(1A) subunit. Although SCA6 shares common features with other neurodegenerative glutamine repeat disorders, the polyglutamine repeats in SCA6 are exceptionally small, ranging from 21 to 33. Because this size is too small to form insoluble aggregates that have been blamed for the cause of neurodegeneration, SCA6 is the disorder suitable for exploring the pathogenic mechanisms other than aggregate formation, whose universal role has been questioned. To characterize the pathogenic process of SCA6, we studied the effects of polyglutamine expansion on channel properties by analyzing currents flowing through the P/Q-type Ca(2+) channels with an expanded stretch of 24, 30, or 40 polyglutamines, recombinantly expressed in baby hamster kidney cells. Whereas the Ca(2+) channels with </=24 polyglutamines showed normal properties, the Ca(2+) channels with 30 or 40 polyglutamines exhibited an 8 mV hyperpolarizing shift in the voltage dependence of inactivation, which considerably reduces the available channel population at a resting membrane potential. The results suggest that polyglutamine expansion in SCA6 leads to neuronal death and cerebellar atrophy through reduction in Ca(2+) influx into Purkinje cells and other neurons. Besides the widely accepted notion that polyglutamine stretches exert toxic effects by forming aggregates, expanded polyglutamines directly alter functions of the affected gene product.

Animals↗

PubMed1999

Molecular and histological evaluation of pancreata from patients with a mitochondrial gene mutation associated with impaired insulin secretion.

A mutation in mitochondrial DNA, which was originally identified in patients with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS), can be associated with a subtype of diabetes mellitus. To determine the molecular and histological basis of impaired insulin secretion in the subjects with this mutation, we studied autopsy pancreata specimens from eight subjects diagnosed as having MELAS. The 3243 bp mutation was identified in seven out of eight pancreata examined. Immunohistochemical studies demonstrated a reduction in total islet mass, and in the numbers of both B and A cells. No evidence of insulitis or apoptosis was found. These data suggested that the 3243 bp mutation may cause the reduction of islet cells, mainly through mechanisms other than autoimmune destruction.

Adolescent↗

PubMed1999

Angiotensin II-induced transactivation of epidermal growth factor receptor regulates fibronectin and transforming growth factor-beta synthesis via transcriptional and posttranscriptional mechanisms.

The signaling cascade elicited by angiotensin II (Ang II) resembles that characteristic of a growth factor, and recent evidence indicates transactivation of epidermal growth factor receptor (EGF-R) by G protein-coupled receptors. Here, we report the involvement of EGF-R in Ang II-induced synthesis of fibronectin and transforming growth factor-beta (TGF-beta) in cardiac fibroblasts. Ang II stimulated fibronectin mRNA levels dose dependently, with a maximal increase (approximately 5-fold) observed after 12 hours of incubation. Fibronectin synthesis induced by Ang II or calcium ionophore was completely abolished by tyrosine kinase inhibitors and intracellular Ca2+ chelating agents. Ang II-induced fibronectin mRNA was not affected by protein kinase C inhibitors or protein kinase C depletion, whereas specific inhibition of EGF-R function by a dominant negative EGF-R mutant and tyrphostin AG1478 abolished induction of fibronectin mRNA. We isolated the rat fibronectin gene, including the 5'-flanking region, and found that the activator protein-1 (AP-1) binding site present in the promoter region was responsible for the Ang II responsiveness of this gene. A gel retardation assay revealed the binding of nuclear protein to the AP-1 site, which was supershifted with anti-c-fos and anti-c-jun but not anti-activating transcription factor (ATF)-2 antibodies. Conditioned medium from Ang II-treated cells contained TGF-beta bioactivity, and addition of neutralizing TGF-beta antibody modestly (46%) inhibited induction of fibronectin. Ang II-induced synthesis of TGF-beta was also abolished by inhibition of EGF-R function. The effect of TGF-beta was exerted by stabilizing fibronectin mRNA without affecting the promoter activity and required de novo protein synthesis. We concluded that Ang II-induced expression of fibronectin and TGF-beta is mediated by downstream signaling of EGF-R transactivated by Ca2+-dependent tyrosine kinase and that Ang II-induced fibronectin mRNA expression is regulated by 2 different mechanisms, which are transcriptional control by binding of the c-fos/c-jun complex to the AP-1 site and posttranscriptional control by mRNA stabilization due to autocrine or paracrine effects of TGF-beta. Thus, this study suggests that the action of Ang II on extracellular matrix formation should be interpreted in association with the EGF-R signaling cascade.

Angiotensin II↗

PubMed1999

A new beta subtype-specific interaction in alpha1A subunit controls P/Q-type Ca2+ channel activation.

The cytoplasmic beta subunit of voltage-dependent calcium channels modulates channel properties in a subtype-specific manner and is important in channel targeting. A high affinity interaction site between the alpha1 interaction domain (AID) in the I-II cytoplasmic loop of alpha1 and the beta interaction domain (BID) of the beta subunit is highly conserved among subunit subtypes. We describe a new subtype-specific interaction (Ss1) between the amino-terminal cytoplasmic domain of alpha1A (BI-2) and the carboxyl terminus of beta4. Like the interaction identified previously () between the carboxyl termini of alpha1A and beta4 (Ss2), the affinity of this interaction is lower than AID-BID, suggesting that these are secondary interactions. Ss1 and Ss2 involve overlapping sites on beta4 and are competitive, but neither inhibits the interaction with AID. The interaction with the amino terminus of alpha1 is isoform-dependent, suggesting a role in the specificity of alpha1-beta pairing. Coexpression of beta4 in Xenopus oocytes produces a reduced hyperpolarizing shift in the I-V curve of the alpha1A channel compared with beta3 (not exhibiting this interaction). Replacing the amino terminus of alpha1A with that of alpha1C abolishes this difference. Our data contribute to our understanding of the molecular organization of calcium channels, providing a functional basis for variation in subunit composition of native P/Q-type channels.

Amino Acid Sequence↗

PubMed1999

Effects of overexpression of PTP36, a putative protein tyrosine phosphatase, on cell adhesion, cell growth, and cytoskeletons in HeLa cells.

Non-receptor-type putative protein tyrosine phosphatase-36 (PTP36), also known as PTPD2/Pez, possesses a domain homologous to the N-terminal half of band 4.1 protein. To gain insight into the biological function of PTP36, we established a HeLa cell line, HtTA/P36-9, in which the overexpression of PTP36 was inducible. PTP36 expressed in HeLa cells was enriched in the cytoskeleton near the plasma membrane. There was little endogenous PTP36 detectable in uninduced HtTA/P36-9 cells or in the parental HeLa cells. Upon induction of PTP36 overexpression, HtTA/P36-9 cells spread less well, grew more slowly, and adhered to the extracellular matrix proteins less well than uninduced cells. Moreover, decreases in the actin stress fibers and the number of focal adhesions were observed. The tyrosine phosphorylation of the focal adhesion kinase induced by lysophosphatidic acid was suppressed in the HtTA/P36-9 cells overexpressing PTP36. These results indicate that PTP36 affects cytoskeletons, cell adhesion, and cell growth, thus suggesting that PTP36 is involved in their regulatory processes.

Cell Adhesion↗

PubMed1999

The Gln27Glu beta2-adrenergic receptor variant is associated with obesity due to subcutaneous fat accumulation in Japanese men.

The Trp64Arg beta3-adrenergic receptor (AR) variant is associated with visceral obesity probably due to decreased lipolysis in visceral fat (H. Kim-Motoyama et al., Diabetologia 40, 469-472, 1997). Functional alteration of beta2AR may also change fat distribution. We investigated the influence of the Gln27Glu beta2AR variant upon obesity and fat distribution. We screened 278 unrelated Japanese men and detected 249 wild-type Gln27 homozygotes, 28 Gln27/Glu27 heterozygotes, and one mutant Glu27 homozygote. The frequency of mutant Glu27 allele was significantly higher in obese subjects than in nonobese/intermediate subjects (0.11 vs 0.04, P = 0. 004). The Gln27/Glu27 heterozygotes had a significantly higher mean age-adjusted body-mass index (BMI) and mean age-adjusted subcutaneous fat area assessed by CT scan than the wild-type homozygotes but not the mean age-adjusted visceral fat areas. In summary, we have found that in Japanese men the Gln27Glu beta2AR variant is associated with obesity due to subcutaneous fat accumulation.

Adipose Tissue↗

PubMed1999

Beneficial effects of the radioprotectant 21-aminosteroid U-74389G in a radiosurgery rat malignant glioma model.

PURPOSE: To evaluate the radioprotectant effects of the 21-aminosteroid U-74389G on the rat C6 glioma model after stereotactic radiosurgery. Because radiosurgery causes both tumor cytotoxicity, as well as regional brain edema, we hypothesized that this drug might exhibit advantageous or deleterious effects on healthy and neoplastic tissue. METHODS: Rats were implanted with 10(6) C6 glioma cells into the right frontal brain and randomized to a Control Group (n = 18), radiosurgery on Day 14 (50% isodose = 35 Gy) (n = 15), or radiosurgery preceded by a single 15 mg/kg intravenous dose of 21-aminosteroid (n = 27). All animals were killed by 90 days and evaluated for survival, tumor size, the presence or absence of regional parenchymal edema, or radiation-induced vasculopathy. RESULTS: After tumor implantation, median survival in the Control Group was 23 days. Significant improvements in median survival were noted after RS alone (median, 31 days; p = 0.02), and RS plus 21-aminosteroid (median, 59 days; p < 0.0001). In the Control Group, mean tumor diameter was 5.4 mm. After RS alone, the mean diameter was 3.2 mm (p = 0.002), and after RS plus 21-aminosteroid, 2.9 mm (p = 0.0002). In the Control Group, the tumor grew as a hypercellular, compact mass. Only 3 of 18 animals had peritumoral edema. In contrast, 7 of 15 animals in the RS group had evidence of edema (p = 0.006), but rats that received 21-aminosteroid showed no increase compared to controls (p = 0.38). Similarly, 6 of 15 animals that had radiosurgery alone showed evidence of vasculopathy (p = 0.005) compared to no animals in the control group and only 2 of 27 aminosteroid-treated animals. CONCLUSIONS: The 21-aminosteroid U-74389G exhibits a radioprotectant effect on normal brain tissue, but does not appear to protect the tumor in an in vivo rat radiosurgery model. We believe that the observed beneficial effects on healthy brain led to significant prolongation of animal survival; perhaps, by limiting the adverse effects of high-dose radiosurgery. This radioprotectant should now be evaluated in randomized clinical trials in patients with malignant brain tumors.

Animals↗