Pharmacological preconditioning with doxorubicin. Implications of heme oxygenase-1 induction in doxorubicin-induced hepatic injury in rats.

Heme oxygenase (HO) is the rate-limiting enzyme in the degradation of heme into biliverdin, carbon monoxide, and iron. HO-1, an inducible form, is thought to contribute to resistance to various types of oxidative stress. Doxorubicin (DOX) produces clinically useful responses in a variety of human cancers. We reported previously that prior administration of DOX ameliorated subsequent hepatic ischemia and reperfusion injury. The aim of this study was to examine whether this pharmacological preconditioning was useful for another type of hepatic injury induced by a non-surgical method. When a high dose of DOX (10 mg/kg body weight) was administered directly to rat liver via the portal vein, serum aspartate transaminase (AST) and alanine transaminase (ALT) levels increased markedly 24 hr after the injection. Under this condition, zinc-protoporphyrin IX, a specific inhibitor of HO-1, caused both serum AST and ALT levels to be elevated further. When a low dose of DOX (5 mg/kg body weight) was administered to rats via the tail vein as pharmacological preconditioning 3 days before the injection of a high dose of DOX via the portal vein, the levels of serum AST and ALT in rats clearly were improved as compared with rats without the preconditioning. Expression of HO-1 in the liver was confirmed 3 days after the administration of a low dose of DOX. In addition, prior administration of zinc-protoporphyrin IX abolished the effect of DOX preconditioning. Immunohistochemical analysis showed that the positive staining of HO-1 protein induced by a low dose of DOX was localized to histiocytes infiltrating periportal areas. These results strongly suggest that pharmacological preconditioning with DOX may generally help to attenuate subsequent oxidant-induced hepatic injury.

The inhibitory effect of vitamin E on 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced DNA injury and the fixation of the DNA injury in mouse lungs.

In order to estimate the effect of vitamin E on DNA injury and K-ras point mutation at an early stage of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone(NNK)-induced lung tumorigenesis in mice, the present study was carried out. Presupplement with vitamin E about 15 times more than control for a week significantly inhibited NNK-induced O6-methylguanine formation in the lungs of mice at 4 and 168 h after the injection. At 30 days after the NNK injection. the activation of K-ras oncogene with a 12th codon GC-->AT transition was detected in 56% of lung samples tested by mutant-allele-specific amplification. Vitamin E supplement reduced the frequency of the mutation to 30%. These results suggest that vitamin E suppresses NNK-induced DNA injury and subsequent fixation of the injury during the initiation and post-initiation phases of the lung tumorigenesis in mice.

Bioactive constituents of Chinese natural medicines. IV. Rhodiolae radix. (2).: On the histamine release inhibitors from the underground part of Rhodiola sacra (Prain ex Hamet) S. H. Fu (Crassulaceae): chemical structures of rhodiocyanoside D and sacranosides A and B.

The methanolic extract of the underground part of Rhodiola sacra (PRAIN ex HAMET) S. H. Fu was found to show inhibitory activity on the histamine release from rat peritoneal exudate cells induced by an antigen-antibody reaction. From the methanolic extract with the inhibitory activity on histamine release, a new cyanoglycoside called rhodiocyanoside D and two new monoterpene glycosides called sacranosides A and B were isolated, together with eight known compounds, rhodiocyanoside A, heterodendrin, lotaustralin, rhodioloside, 2-phenylethyl alpha-L-arabinopyranosyl(1-->6)-beta-D-glucopyranoside, 2-methyl-3-buten-2-yl beta-D-glucopyranoside, kenposide A, and rhodiooctanoside. The structures of new compounds were determined on the basis of chemical and physicochemical evidence, which included the synthesis of sacranoside A from (-)-myrtenol. All major chemical constituents from R. sacra inhibited the histamine release and, among them, lotaustralin and rhodiooctanoside were found to show potent inhibitory activity.

Molecular cloning of rat p38 mitogen-activated protein kinase and it's osmotic regulation in rat kidney.

Rat p38 mitogen-activated protein (MAP) kinase cDNA was isolated from rat kidney cDNA library using a PCR cloning strategy. The deduced amino acid sequence consists of 360 amino acids and shares 95.3% similarity with human p38 MAP kinase. The message for rat p38 MAP kinase was about 3.4 kilobases and was highly expressed in the kidney. In water-deprived rat kidneys, the steady-state levels of p38 MAP kinase mRNA increased about 2.7-fold as compared with those of control rats. This result suggests that p38 MAP kinase may play an important role in the osmoregulation in the kidney.

Molecular cloning and characterization of a novel truncated from (ClC-2 beta) of ClC-2 alpha (ClC-2G) in rabbit heart.

Two cDNAs encoding rabbit heart Cl- channels (rabClC-2 beta and rabClC-2 alpha) were isolated by a PCR cloning strategy. RabClC-2 beta is a novel cDNA consisting of 2998 bp and encoding the 822-amino acid protein, while rabClC-2 alpha is identical to previously reported ClC-2G. RabClC-2 beta is 68 amino acids truncated from NH2-terminus of rabClC-2 alpha, but all 13 putative hydrophobic domains are conserved in rabClC-2 beta. Although rabClC-2 alpha was suggested to be activated by extracellular hypotonicity, expression of rabClC-2 beta in Xenopus oocytes induced large Cl- currents even in the absence of extracellular hypotonicity. Induction of external hypotonicity did not further increase the amplitude of membrane currents. On the other hand, as similar to rabClC-2 alpha, rabClC-2 beta current was augmented by PKA activation. Thus, different RNA processing of the same gene appears to provide two highly homologous PKA-activated Cl- channels with or without responsiveness to cell swelling in rabbit heart.