Granulocyte-colony stimulating factor enhances load-induced muscle hypertrophy in mice.

Granulocyte-colony stimulating factor (G-CSF) is a cytokine crucially involved in the regulation of granulopoiesis and the mobilization of hematopoietic stem cells from bone marrow. However, emerging data suggest that G-CSF exhibits more diverse functions than initially expected, such as conferring protection against apoptosis to neural cells and stimulating mitogenesis in cardiomyocytes and skeletal muscle stem cells after injury. In the present study, we sought to investigate the potential contribution of G-CSF to the regulation of muscle volume. We found that the administration of G-CSF significantly enhances muscle hypertrophy in two different muscle overload models. Interestingly, there was a significant increase in the transcripts of both G-CSF and G-CSF receptors in the muscles that were under overload stress. Using mutant mice lacking the G-CSF receptor, we confirmed that the anabolic effect is dependent on the G-CSF receptor signaling. Furthermore, we found that G-CSF increases the diameter of myotubes in vitro and induces the phosphorylation of AKT, mTOR, and ERK1/2 in the myoblast-like cell line C2C12 after differentiation induction. These findings indicate that G-CSF is involved in load-induced muscle hypertrophy and suggest that G-CSF is a potential agent for treating patients with muscle loss and sarcopenia.

Hepatocyte nuclear factor 4α is a critical factor for the production of complement components in the liver.

The complement system plays an important role in biological defense as an effector to eliminate microorganisms that invade an organism and it is composed of more than 50 proteins, most of which are produced in the liver. Of these proteins, the mRNA expression of C3 and Cfb is known to be positively regulated by the nuclear receptor HNF4α. To investigate whether HNF4α regulates the complement system, we analyzed the hepatic expression of genes involved in the complement activation pathway and membrane attack complex (MAC) formation within the complement system using liver-specific Hnf4a-null mice (Hnf4aΔHep mice) and tamoxifen-induced liver-specific Hnf4a-null mice (Hnf4af/f;AlbERT2cre mice). We found that hepatic expression of many complement genes including C8a, C8b, C8g, and C9 that are involved in formation of the MAC was markedly decreased in Hnf4aΔHep mice and Hnf4af/f;AlbERT2cre mice. Furthermore, expression of C8A, C8B, and C8G was also decreased in human hepatoma cell lines in which the expression of HNF4α was suppressed, and expression of C8G and C9 was induced in a human immortalized hepatocyte cell line with forced expression of HNF4α. Transactivation of C8g and C9 was dependent on HNF4α expression of HNF4α binding sites, indicating that C8g and C9 are novel target genes of HNF4α. The results suggest that hepatic HNF4α plays an important role in regulation of the complement system, mainly MAC formation.

Microdialysis detection of lactate in subcutaneous tissue as a reliable indicator of tissue metabolic disorders in an animal sepsis model.

PURPOSE: Tissue dysoxia is thought to be a fundamental cause of the organ failure that occurs as a result of shock. Plasma lactate has been frequently measured as an indicator of the state of systemic tissue metabolism. On the other hand, tissue lactate levels can directly indicate a disorder in the state of cytological tissue metabolism. The continuous monitoring of lactate levels in subcutaneous tissue will reflect the state of tissue dysoxia more precisely than levels of lactate in the plasma lactate. We have investigated the differences in the levels of plasma and tissue lactate using a microdialysis (MD) technique in an animal septic shock model. METHOD: Male 8-week-old Wistar/ST rats were used. We prepared an animal model by injection of lipopolysaccharide (LPS) into the abdominal cavity. LPS was given to 9 animals in the experimental group while physiological saline was given to 6 animals in the control group. A MD probe was used to quantify the lactate levels in the subcutaneous tissue. The mean arterial pressure, blood gas content and lactate levels were measured every 50 min up to 400 min after injection and compared between both groups. RESULT: The MAP of both groups showed similar changes after injection. Plasma lactate levels in the LPS group showed a significant increase after 100 min and reached a plateau from 150 min to 250 min. Subcutaneous lactate in the LPS group showed a significant increase after 150 min. Subcutaneous pyruvate in the LPS group showed a significant increase after 100 min. The lactate/pyruvate (L/P) ratio in the subcutaneous tissue showed a sustained increase from 300 min in the LPS group. CONCLUSION: Monitoring plasma lactate levels is useful for the early assessment of anaerobic metabolism before hypotension. Plasma lactate levels did not increase during some periods. This phenomenon was due to the balance between production and utilization. However, tissue lactate showed a chronological increase. These results suggest that the measurement of tissue lactate levels is reliable for assessing local energy metabolic disturbances. Under conditions of septic shock, an increase in lactate levels was found to be a sensitive marker of tissue metabolism disorder.

Utility of microdialysis to detect the lactate/pyruvate ratio in subcutaneous tissue for the reliable monitoring of hemorrhagic shock.

The present experiments were carried out to investigate the usefulness of measuring peripheral tissue metabolism for the clinical assessment of shock. Male Wistar/ST rats (8 weeks-old) were used. All rats were placed in a supine position while anesthetized. A tube for measuring arterial pressure and collecting blood samples was cannulated into the femoral artery. For microdialysis, the introducer was inserted into the subcutaneous tissue in the abdominal wall. Blood was exsanguinated to maintain the mean arterial pressure at 40 +/- 5 mmHg. Mean arterial pressure, arterial blood gas and serum lactate levels were measured. Microdialysis was performed to quantify the levels of lactate and pyruvate in the subcutaneous tissue. Six rats died due to hemorrhagic shock by 350 min (Group D) while six rats had survived for the 350 min period after exsanguination (Group A). These data was obtained at intervals of 50 min after exsanguination up to a period of 250 min and compared between Groups A and D. In Group A, serum lactate levels did not increase throughout the entire period of observation. Serum lactate levels in Group D transiently increased, but did not show a dramatic increase during the blood pressure maintenance period. In particular, serum lactate levels increased again after a period of more than 150 min following exsanguination. Lactate levels in the subcutaneous tissue gradually increased and were significantly higher in Group D than that in Group A after 150 min. The L/P ratio in Group A remained fairly constant during the period of observation. In contrast, the L/P ratio in Group D increased gradually, and was significantly higher than that in Group A after 100 min. It was concluded that the continuous increase in the L/P ratio in the subcutaneous tissue in Group D was indicative of tissue circulatory failure and of an abnormality in tissue oxygen metabolism prior to the detection of the collapse of compensatory mechanisms appearing in the vital signs. These findings suggest that measuring the L/P ratio is useful for the clinical assessment and monitoring of shock.

Sorption of Co(II), Ni(II), and Zn(II) on biogenic manganese oxides produced by a Mn-oxidizing fungus, strain KR21-2.

The characteristics of Co(II), Ni(II), and Zn(II) sorption on freshly produced biogenic Mn oxides by a Mn-oxidizing fungus, strain KR21-2, were investigated. The biogenic Mn oxides showed about 10-fold higher efficiencies for sorbing the metal ions than a synthetic Mn oxide (gamma-MnO2) on the basis of unit weight and unit surface area. The order of sorption efficiency on the biogenic Mn oxides was Co(II) > Zn(II) > Ni(II), while that on the synthetic Mn oxide was Zn(II) > Co(II) > Ni(II). These sorption selectivities were confirmed by both sorption isotherms and competitive sorption experiments. Two-step extraction, using 10mM CuSO4 solution for exchangeable sorbed ions and 10-20mM hydroxylamine hydrochloride for ions bound to reducible Mn oxide phase, showed higher irreversibility of Co(II) and Ni(II) sorption on the biogenic Mn oxides while Zn(II) sorption was mostly reversible (Cu(II)-exchangeable). Sorptions of Co(II), Ni(II), and Zn(II) on the synthetic Mn oxide were, however, found to be mostly reversible. Higher irreversibility of Co(II) and Ni(II) sorption on the biogenic Mn oxides may partly explain higher accumulation of these metal ions in Mn oxide phases in natural environments. The results obtained in this study raise the possibility to applying the biogenic Mn oxide formation to treatment of water contaminated with toxic metal ions.

Interaction of inorganic arsenic with biogenic manganese oxide produced by a Mn-oxidizing fungus, strain KR21-2.

In batch culture experiments we examined oxidation of As(III) and adsorption of As(III/V) by biogenic manganese oxide formed by a manganese oxide-depositing fungus, strain KR21-2. We expected to gain insight into the applicability of Mn-depositing microorganisms for biological treatment of As-contaminated waters. In cultures containing Mn2+ and As(V), the solid Mn phase was rich in bound Mn2+ (molar ratio, approximately 30%) and showed a transiently high accumulation of As(V) during the early stage of manganese oxide formation. As manganese oxide formation progressed, a large proportion of adsorbed As(V) was subsequently released. The high proportion of bound Mn2+ may suppress a charge repulsion between As(V) and the manganese oxide surface, which has structural negative charges, promoting complex formation. In cultures containing Mn2+ and As(III), As(III) started to be oxidized to As(V) after manganese oxide formation was mostly completed. In suspensions of the biogenic manganese oxides with dissolved Mn2+, As(III) oxidation rates decreased with increasing dissolved Mn2+. These results indicate that biogenic manganese oxide with a high proportion of bound Mn2+ oxidizes As(III) less effectively than with a low proportion of bound Mn2+. Coexisting Zn2+, Ni2+, and Co2+ also showed similar effects to different extents. The present study demonstrates characteristic features of oxidation and adsorption of As by biogenic manganese oxides and suggests possibilities of developing a microbial treatment system for water contaminated with As that is suited to the actual situation of contamination.