Associations of cadmium with zinc and copper in cancer cases and controls

This study was performed in order to search for possible associations between cadmium (Cd) and other metals~ Cd, zinc (Zn), and copper (Cu) levels of renal cortex and liver samples obtained from 196 cancer cases and 198 noncancer controls were analyzed in eight regional institutes in Japan. Cd, Zn, and Cu concentrations in liver and renal cortex of the selected cancer cases were compared to the controls whose localities, age, and sex were matched with the cancer cases. The cancer cases clearly showed higher accumulations of Zn in liver and renal cortex than the noncancer group. Cd showed a similar tendency, but there was no statistical significance between case and control subjects. There was no marked difference in Cu accumulation between the pairs. The best fit regression curve of Zn to Cd on a molar basis in renal cortex was obtained. Curvilinear regression equations of Zn to Cd for both cancer and noncancer groups were drawn. From these two equations, the Zn level of the cancer cases was found to reach a maximum when the Cd level showed 1.4 mmol/kg (157 pxg/g), whereas Zn in the noncancer group peaked at 1.6 mmol/kg (180 Ixg/g) of Cd in renal cortex. This may suggest that excessive Cd accumulation deprives binding sites of Zn in renal cortex when both metals are saturated.     

Hic-5, an adaptor protein expressed in vascular smooth muscle cells, modulates the arterial response to injury in vivo

Focal adhesion components are targets for biochemical and mechanical stimuli that evoke crucial injury. Hic-5 (hydrogen peroxide-inducible clone 5) is a multidomain adaptor protein which is implicated in the regulation of integrin signaling in focal adhesion. The aim of this research was to test the hypothesis that Hic-5, a focal adhesion LIM protein expressed in smooth muscle cells, is involved in dynamic processes by pathological stimuli in the vessel wall. Here, we describe the analysis of the function of Hic-5 using a mouse model of vascular injury that may mimic balloon angioplasty. At 4 days after vascular injury, marked down-regulation of the Hic-5 expression was observed in the smooth muscle layer, and local delivery of the Hic-5 using adenovirus vectors repressed injury-induced neointimal expansion. In addition, Hic-5 reduced cells migration into three-dimensional collagen gels, and the forced expression of Hic-5 in cells embedded in the collagen gel matrix repressed the expression of uPA that participates in smooth muscle cell migration. These results suggest that Hic-5 modulates cellular responses to pathological stimuli in the vessel wall.     

Branched-Chain Amino Acids Enhance Premature Senescence through Mammalian Target of Rapamycin Complex I-Mediated Upregulation of p21 Protein

Branched-chain amino acids (BCAAs) have been applied as an oral supplementation to patients with liver cirrhosis. BCAAs not only improve nutritional status of patients but also decrease the incidence of liver cancer. Mammalian target of rapamycin (mTOR) links cellular metabolism with growth and proliferation in response to nutrients, energy, and growth factors. BCAAs, especially leucine, have been shown to regulate protein synthesis through mTOR activities. On the other hand, cellular senescence is suggested to function as tumor suppressor mechanisms, and induced by a variety of stimuli including DNA damage-inducing drugs. However, it is not clear how BCAA supplementation prevents the incidence of liver cancer in patients with cirrhosis. Here we showed that human cancer cells, HepG2 and U2OS, cultured in medium containing BCAAs with Fischer''s ratio about 3, which was shown to have highest activities to synthesize and secrete of albumin, had higher activities to induce premature senescence and elevate mTORC1 activities. Furthermore, BCAAs themselves enhanced the execution of premature senescence induced by DNA damage-inducing drugs, which was effectively prevented by rapamycin. These results strongly suggested the contribution of the mTORC1 pathway to the regulation of premature senescence. Interestingly, the protein levels of p21, a p53 target and well-known gene essential for the execution of cellular senescence, were upregulated in the presence of BCAAs. These results suggested that BCAAs possibly contribute to tumor suppression by enhancing cellular senescence mediated through the mTOR signalling pathway.     

Evidence for essential disulfide bonds in the β-subunit of (Na+ + K+)-ATPase

$\text{(Na}{}^{\mathrm{+}}\text{+ K}{}^{\mathrm{+}}\text{)-ATPase}$ from dog kidney lost its activity when heated at 55°C in the presence of 0.3 M 2-mercaptoethanol. Either heat treatment alone or addition of reducing agent at around 25°C caused little inactivation. One disulfide bond per protomer (mol. wt. 146000) was reduced in the inactivated sample but in active samples no reduction occurred. Neither K⁺-dependent phosphatase activity nor phosphoenzyme formation in the presence of Na⁺ was detected in the inactivated sample, suggesting that the disulfide bond was essential for the catalytic cycle of $\text{(Na}{}^{\mathrm{+}}\text{+ K}{}^{\mathrm{+}}\text{)-ATPase}$. This essential disulfide bond belonged to the β-subunit, the glycoprotein component of the enzyme, indicating that the β-subunit may be an integral component of the $\text{(Na}{}^{\mathrm{+}}\text{+ K}{}^{\mathrm{+}}\text{)-ATPase}$ system.     

Long chain fatty acid utilization of T-cells from autoimmune MRL-lpr/lpr mice

To test the hypothesis that T-cells which exhibit abnormal immunological behavior manifest derangements in the de novo synthesis of phospholipids, the utilization of [³H]palmitic acid in B220⁺ T-cells from autoimmune MRL-lpr/lpr mice was investigated. The rate of incorporation of [³H]palmitic acid into membrane phospolipids was markedly increased in intact B220⁺ T-cells compared to that in T-cells from immunologically normal mice. The activities of two key enzymes involved in the de novo synthesis of palmitoyl-phospholipids, acyl-coenzyme (CoA) ligase and acyl-CoA: sn-glycerol-3-phosphate acyl transferase, were significantly higher in homgenates from B220⁺ T-cell membranes compared with those in controls. Depsite these findings, the molar concentration of individual palmitoyl glycerolipids was equivalent in the membranes of B220⁺ T-cells and control lymph node T-cells. The results indicate that T-cells from lupus mice exhibit complex defects in the biosynthesis and turnover of membrane phospholipids and suggest the possibility that these aberrations contribute to T-cell dysfunction in autoimmune diseases.     

New Members of the Mammalian Glycerophosphodiester Phosphodiesterase Family: GDE4 AND GDE7 PRODUCE LYSOPHOSPHATIDIC ACID BY LYSOPHOSPHOLIPASE D ACTIVITY*

The known mammalian glycerophosphodiester phosphodiesterases (GP-PDEs) hydrolyze glycerophosphodiesters. In this study, two novel members of the mammalian GP-PDE family, GDE4 and GDE7, were isolated, and the molecular basis of mammalian GP-PDEs was further explored. The GDE4 and GDE7 sequences are highly homologous and evolutionarily close. GDE4 is expressed in intestinal epithelial cells, spermatids, and macrophages, whereas GDE7 is particularly expressed in gastro-esophageal epithelial cells. Unlike other mammalian GP-PDEs, GDE4 and GDE7 cannot hydrolyze either glycerophosphoinositol or glycerophosphocholine. Unexpectedly, both GDE4 and GDE7 show a lysophospholipase D activity toward lysophosphatidylcholine (lyso-PC). We purified the recombinant GDE4 and GDE7 proteins and show that these enzymes can hydrolyze lyso-PC to produce lysophosphatidic acid (LPA). Further characterization of purified recombinant GDE4 showed that it can also convert lyso-platelet-activating factor (1-O-alkyl-sn-glycero-3-phosphocholine; lyso-PAF) to alkyl-LPA. These data contribute to our current understanding of mammalian GP-PDEs and of their physiological roles via the control of lyso-PC and lyso-PAF metabolism in gastrointestinal epithelial cells and macrophages.     

Host defense in Nicrophorus quadripunctatus against brood parasitism by Ptomascopus morio (Coleoptera: Silphidae: Nicrophorinae)

Few studies have been conducted on the host defenses of insects against brood parasitism. We investigated whether the silphid beetle Ptomascopus morio, a brood parasite of related silphid species Nicrophorus concolor, can also parasitize another silphid species Nicrophorus quadripunctatus and the manner in which N. quadripunctatus defends itself against parasitism. Successful brood parasitism under natural conditions was not observed at the time of year when P. morio and N. quadripunctatus are both reproductively active. Follow-up experiments revealed that P. morio attempts to oviposit near N. quadripunctatus nests, but is rarely successful if adult hosts are present. When P. morio larvae were experimentally introduced to N. quadripunctatus broods, some P. morio larvae survived when the host and parasite larvae were at the same stage. We concluded that N. quadripunctatus defends itself against brood parasitism in two ways: (1) potential brood parasites are repelled, thus limiting their access to the resource; and (2) the young of the parasitic species are killed.