O(2)- and H(2)O(2)-dependent verdoheme degradation by heme oxygenase: reaction mechanisms and potential physiological roles of the dual pathway degradation

Heme oxygenase (HO) catalyzes the catabolism of heme to biliverdin, CO, and a free iron through three successive oxygenation steps. The third oxygenation, oxidative degradation of verdoheme to biliverdin, has been the least understood step despite its importance in regulating HO activity. We have examined in detail the degradation of a synthetic verdoheme IXalpha complexed with rat HO-1. Our findings include: 1) HO degrades verdoheme through a dual pathway using either O(2) or H(2)O(2); 2) the verdoheme reactivity with O(2) is the lowest among the three O(2) reactions in the HO catalysis, and the newly found H(2)O(2) pathway is approximately 40-fold faster than the O(2)-dependent verdoheme degradation; 3) both reactions are initiated by the binding of O(2) or H(2)O(2) to allow the first direct observation of degradation intermediates of verdoheme; and 4) Asp(140) in HO-1 is critical for the verdoheme degradation regardless of the oxygen source. On the basis of these findings, we propose that the HO enzyme activates O(2) and H(2)O(2) on the verdoheme iron with the aid of a nearby water molecule linked with Asp(140). These mechanisms are similar to the well established mechanism of the first oxygenation, meso-hydroxylation of heme, and thus, HO can utilize a common architecture to promote the first and third oxygenation steps of the heme catabolism. In addition, our results infer the possible involvement of the H(2)O(2)-dependent verdoheme degradation in vivo, and potential roles of the dual pathway reaction of HO against oxidative stress are proposed.     

Phencyclidine-induced expression of c-Fos-like immunoreactivity in mouse brain regions

For the purpose of studying a role of immediate early genes in psychotomimetic-induced behavioral excitation, we experimentally enhanced the locomotor activity of mice by acute administration of phencyclidine and examined the expression and localization of the c-Fos-like and c-Jun-like immunoreactivities in brain regions. A single injection of phencyclidine (5.0 mg/kg, i.p.) significantly increased not only the locomotor activity but also the expression of c-Fos-like immunoreactivity in several brain regions, particularly in the parietal cortex, hippocampal dentate gyrus, piriform cortex and hypothalamus. Interestingly, the c-Fos-like immunoreactivity in the parietal cortex continued to increase for 1 week after the phencyclidine injection. These results indicate that phencyclidine, even injected only once, can induce the persistent expression of c-Fos or c-Fos-related protein(s) in the mouse brain, and also suggest the possibility that such a c-Fos expression may underlie the behavioral and/or psychotomimetic effects of phencyclidine.     

Peduncle of Hydra and the heart of higher organisms share a common ancestral origin

The heart is assumed to have evolved as the organ for pumping blood. Here we report a pumping phenomenon in Hydra, a member of the phylum Cnidaria. We find that the peduncle, lower quarter of the body column, stores most of the gastrovascular fluid when the animal is an elongate form. Upon contraction of the polyp, the peduncle contracts and transfers the fluid into the rest of the cavity. We also find that Hydra RFamide III, a homolog of cardioexcitatory RFamide neuropeptides in higher organisms, elevates this transfer activity. Further, CnNk-2, a homolog of a cardiomuscular tissue marker Nkx-2.5, is expressed in the endodermal tissue of the peduncle. These observations indicate that the transfer of fluid by the peduncle has a similar neurological and genetic basis to the pumping of blood by the heart, suggesting that the Hydra peduncle and the heart of higher organisms share a common ancestral origin.     

Associations among Erythroferrone and Biomarkers of Erythropoiesis and Iron Metabolism,and Treatment with Long-Term Erythropoiesis-Stimulating Agents in Patients on Hemodialysis

Background

We aimed to identify associations between erythroferrone (ERFE), a regulator of hepcidin 25, and biomarkers of erythropoiesis and iron metabolism. We also aimed to determine the effects of erythropoiesis-stimulating agents (ESA), continuous erythropoietin receptor activator (CERA) and darbepoetin-α (DA) on ERFE production in patients on hemodialysis (HD).

Methods

Blood samples were obtained from 59 patients before HD sessions on day 0 (baseline). Twenty patients who were injected with either CERA (N = 10) or DA (N = 10) at the end of the dialysis week (day 0), who had ferritin ≥ 100 ng/mL and/or transferrin saturation ≥ 20%, and hemoglobin > 9 g/dL were selected from among the 59 patients. Blood was sampled serially before HD sessions on days 3, 5, 7 from patients on DA and on the same days plus day 14 from those on CERA.

Results

Levels of ERFE correlated inversely with those of hepcidin 25 and ferritin, and positively with those of soluble transferrin receptor. The hepcidin 25: ERFE ratio and hepcidin 25 levels positively correlated with ferritin levels. Levels of ERFE significantly increased from day 3 of treatment with DA and CERA and decreased by days 7 and 14, respectively. Erythropoiesis-stimulating agents concomitantly decreased levels of hepcidin 25 as those of ERFE increased.

Conclusion

We identified a novel association between ESA and ERFE in patients on HD. Both DA and CERA increased levels of ERFE that regulated hepcidin 25 and led to iron mobilization from body stores during erythropoiesis.     

Protocol for the production of viable bimaternal mouse embryos

A reliable nuclear transfer method was first reported in 1983; it provided definite evidence that parthenogenetic embryos are lethal at early postimplantation in mammals. Subsequently, nuclear transfer has been extensively used as an important and versatile tool for investigating embryo and somatic-cell cloning and nucleo-cytoplasmic interactions. Further development of this technique has enabled the generation of bimaternal embryos containing two haploid sets of maternal genomes from female germ cells of different origins. By using a 2-d nuclear transfer system for oocyte reconstruction, viable mice can be produced solely from maternal genomes, without the participation of the paternal genome. This oocyte reconstruction system, as described in this protocol, could provide valuable guidelines for exploring the potential endowments of gametes and for conferring novel properties to them.     

Stimulative and inhibitory effects of bacteria on the growth of microalgae

Several examples of stimulative and inhibitoryeffects of bacteria on microalgal growth areintroduced, and the importance of bacteria in algalmass culture is investigated. Diatoms are often usedas live food for planktonic larvae of sea urchin andbivalves. Monodispersed Chaetoceros ceratosporum hasbeen cultivated by using clean, high nutrient content,deep seawater (DSW). However, the growth rate and cellyield of diatoms fluctuated, to relatively largeextent, with the season that DSW was collected. Whensome bacterial strains isolated from DSW were added tothe culture, diatom growth was often stimulated and arelatively constant cell yield was obtained. Anotherdiatom species, C. gracilis, was also stimulated byadding some bacterial strains to cultures. Thepositive effect of bacteria on diatoms was observednot only for planktonic species, but also on attachedspecies. A benthic diatom, Nitzschia sp., wasstimulated by a bacterial film of Alcaligenes on thesurface of the substratum. On the other hand, a strainof Flavobacterium sp. isolated from natural seawaterduring the decline period of an algal bloom had a strongalgicidal effect on the red tide plankton,Gymnodinium mikimotoi. Recent reports demonstratethat many bacterial strains have significantalgicidal effects on many species of red tideplankton. These results indicate that bacterialeffects should be taken into account to obtain stablemass culture of food microalgae.     

Knockout of the SREBP system increases production of the polyketide FR901512 in filamentous fungal sp. No. 14919 and lovastatin in Aspergillus terreus ATCC20542

Applied Microbiology and Biotechnology - In the production of useful microbial secondary metabolites, the breeding of strains is generally performed by random mutagenesis. However, because random...     

The mitochondrial Ca2+ uptake regulator,MICU1, is involved in cold stress‐induced ferroptosis

Ferroptosis has recently attracted much interest because of its relevance to human diseases such as cancer and ischemia‐reperfusion injury. We have reported that prolonged severe cold stress induces lipid peroxidation‐dependent ferroptosis, but the upstream mechanism remains unknown. Here, using genome‐wide CRISPR screening, we found that a mitochondrial Ca²⁺ uptake regulator, mitochondrial calcium uptake 1 (MICU1), is required for generating lipid peroxide and subsequent ferroptosis under cold stress. Furthermore, the gatekeeping activity of MICU1 through mitochondrial calcium uniporter (MCU) is suggested to be indispensable for cold stress‐induced ferroptosis. MICU1 is required for mitochondrial Ca²⁺ increase, hyperpolarization of the mitochondrial membrane potential (MMP), and subsequent lipid peroxidation under cold stress. Collectively, these findings suggest that the MICU1‐dependent mitochondrial Ca²⁺ homeostasis‐MMP hyperpolarization axis is involved in cold stress‐induced lipid peroxidation and ferroptosis.     

Differential Distribution of Posttranslationally Modified Microtubules in Osteoclasts

The differential distribution of microtubules in osteoclasts in culture was examined by using antibodies against acetylated, tyrosinated, or detyrosinated tubulins. Tyrosinated tubulin was found throughout the cytoplasmic microtubules in all cells examined. An expanding protrusion that contained tyrosinated tubulin but none of the detyrosinated or acetylated form was seen in the immature osteoclasts. Detyrosinated or acetylated tubulin was detectable in the peripheral cytoplasm of the mature osteoclasts displaying the loss of the expanding protrusion. Although most of the microtubules were derived from the centrosome, noncentrosomal microtubules were distributed in the expanding protrusion, which was predominantly positive for tyrosinated tubulin. By tracing single microtubules, the authors found that their growing ends were always rich in tyrosinated tubulin subunits. End binding protein 1 bound preferentially to the microtubule ends. Both acetylated and tyrosinated microtubules were shown to be closely associated with podosomes. Microtubules appeared to grow over or into the podosomes; in addition, the growing ends of single microtubules could be observed to target the podosomes. Moreover, a microtubule-associated histone deacetylase 6 was localized in the podosomes of the osteoclast. On the basis of these results, the authors conclude that posttranslational modifications of microtubules may correlate with characteristic changes in podosome dynamics in osteoclasts.