BBA - Molecular Basis of Disease (v.1782, #2)

Stem cells, cell transplantation and liver repopulation by Michael Oertel; David A. Shafritz (61-74).
Liver transplantation is currently the only therapeutic option for patients with end-stage chronic liver disease and for severe acute liver failure. Because of limited donor availability, attention has been focused on the possibility to restore liver mass and function through cell transplantation. Stem cells are a promising source for liver repopulation after cell transplantation, but whether or not the adult mammalian liver contains hepatic stem cells is highly controversial. Part of the problem is that proliferation of mature adult hepatocytes is sufficient to regenerate the liver after two-thirds partial hepatectomy or acute toxic liver injury and participation of stem cells is not required. However, under conditions in which hepatocyte proliferation is blocked, undifferentiated epithelial cells in the periportal areas, called “oval cells”, proliferate, differentiate into hepatocytes and restore liver mass. These cells are referred to as facultative liver stem cells, but they do not repopulate the normal liver after their transplantation. In contrast, epithelial cells isolated from the early fetal liver can effectively repopulate the normal liver, but they are already traversing the hepatic lineage and may not be true stem cells. Mesenchymal stem cells and embryonic stem cells can be induced to differentiate along the hepatic lineage in culture, but at present these cells are inefficient in repopulating the liver. This review will characterize these various cell types and compare the properties of these cells and the conditions under which they do or do not repopulate the liver following their transplantation.
Keywords: Stem/progenitor cell; Bipotency; Oval cell; Cell transplantation; Liver repopulation;

Analyses of functional interaction between RECQL1, RECQL5, and BLM which physically interact with DNA topoisomerase IIIα by Makoto Otsuki; Masayuki Seki; Eri Inoue; Takuya Abe; Yoshiyasu Narita; Akari Yoshimura; Shusuke Tada; Yutaka Ishii; Takemi Enomoto (75-81).
RECQL1 and RECQL5 as well as BLM reportedly interact with TOP3α whose defect is lethal for the cell. Therefore in this study, we characterized recql5/recql1/blm triple mutants from DT40 cells to determine whether the triple mutants show a top3α disrupted cell-like phenotype. The triple mutants are viable. Moreover, both blm/recql1 and recql5/blm cells, and recql5/recql1/blm cells grew slightly slower than blm cells, that is, triple mutant cells grew almost the same rate as either of the double mutant cells. The blm cells showed sensitivity to methyl methanesulfonate (MMS) and ultraviolet light (UV), about a 10-fold increase in sister chromatid exchange (SCE), and about a 3-fold increase in damage-induced mitotic chiasma compared to wild-type cells. The triple mutants showed the same sensitivity to MMS or UV and the same frequency of damage-induced mitotic chiasma compared to those of blm cells, indicating that unlike BLM, RECQL1 and RECQL5 play a little role in the repair of or tolerance to DNA damages. However, recql5/blm cells showed higher frequency of SCE than blm cells, whereas the RECQL1 gene disruption had no effect on SCE in blm cells and even in recql5/blm cells.
Keywords: RECQL1; RECQL5; BLM; RECQ; DT40;

Proliferative actions of muscarinic receptors expressed in macrophages derived from normal and tumor bearing mice by Eulalia de la Torre; Ana M. Genaro; María L. Ribeiro; Romina Pagotto; Omar P. Pignataro; María E. Sales (82-89).
Macrophages (Mps) are essential cellular components of the innate immune system. They are released from the bone marrow as immature monocytes and after circulating in the blood stream, migrate into tissues to undergo final differentiation into resident Mps. In general terms Mps behavior in breast tumors, was described as being either for or against tumor growth. Under certain well defined circumstances Mps are able to kill cells in two ways: direct tumor cytotoxicity or antibody dependent cytotoxicity. We had previously demonstrated that peritoneal Mps from LMM3 mammary tumor bearing mice (TMps) enhanced in vivo the LMM3 induced angiogenesis, promoting tumor growth while Mps from normal BALB/c mice (NMps) did not. In this work, we demonstrate that Mps, expressing functional muscarinic acetylcholine receptors, are able to proliferate in vitro in response to the muscarinic agonist carbachol. These peritoneal cells use two distinct metabolic pathways: TMps are primed by tumor presence and they proliferate mainly by activating arginase pathway and by producing high levels of prostaglandin E2 via M1–M3 receptors activation. In NMps, carbachol stimulates M2 receptors function, triggering protein kinase C activity and induces moderate prostaglandin E2 liberation via M1 receptor.
Keywords: Muscarinic receptor; Macrophage; Proliferation; Arginase; Cyclooxygenase; Protein kinase C;

The effects of frataxin silencing in HeLa cells are rescued by the expression of human mitochondrial ferritin by Isabella Zanella; Manuela Derosas; Marcella Corrado; Emiliano Cocco; Patrizia Cavadini; Giorgio Biasiotto; Maura Poli; Rosanna Verardi; Paolo Arosio (90-98).
Frataxin is a ubiquitous mitochondrial iron-binding protein involved in the biosynthesis of Fe/S clusters and heme. Its deficiency causes Friedreich's ataxia, a severe neurodegenerative disease. Mitochondrial ferritin is another major iron-binding protein, abundant in the testis and in sideroblasts from patients with sideroblastic anemia. We previously showed that its expression rescued the defects caused by frataxin deficiency in the yeast. To verify if this occurs also in mammals, we silenced frataxin in HeLa cells. This caused a reduction of growth, inhibition of the activity of aconitase and superoxide dismutase-2 and reduction of cytosolic ferritins without alteration of mitochondrial iron content. None of these effects were evident when silencing was done in cells expressing mitochondrial ferritin. These data indicate that frataxin has some roles in controlling the balance between different mitochondrial iron pools that are partially in common with those of mitochondrial ferritin.
Keywords: Iron; Frataxin; Ferritin; Mitochondrial iron; Aconitase;

Adiponectin and leptin are secreted through distinct trafficking pathways in adipocytes by Linglin Xie; Cormac P. O'Reilly; Stephen K. Chapes; Silvia Mora (99-108).
Adiponectin and leptin are two adipokines secreted by white adipose tissue that regulate insulin sensitivity. Previously we reported that adiponectin but not leptin release depends on GGA-coated vesicle formation, suggesting that leptin and adiponectin may follow different secretory routes. Here we have examined the intracellular trafficking pathways that lead to the secretion of these two hormones. While adiponectin and leptin displayed distinct localization in the steady-state, treatment of adipocytes with brefeldin A inhibited both adiponectin and leptin secretion to a similar level, indicating a common requirement for class III ADP-ribosylating factors and an intact Golgi apparatus. Adiponectin secretion was significantly reduced by endosomal inactivation in both 3T3L1 and rat isolated adipocytes, whereas this treatment had no effect on leptin secretion. Importantly, endosomal inactivation completely abolished the insulin stimulatory effect on adiponectin release in rat adipocytes. Confocal microscopy studies revealed colocalization of adiponectin with endogenous rab11 a marker for the recycling endosome, and with expressed rab5-GFP mutant (rab5Q75L) a marker for the early endosome compartment. Colocalization of adiponectin and rab5Q75L was increased in endosome inactivated cells. Consistent with these findings adiponectin secretion was reduced in cells expressing mutants of Rab11 and Rab5 proteins. In contrast, expression of an inactive (kinase dead) mutant of Protein Kinase D1 moderately but significantly inhibited leptin secretion without altering adiponectin secretion. Taken together, these results suggest that leptin and adiponectin secretion involve distinct intracellular compartments and that endosomal compartments are required for adiponectin but not for leptin secretion.
Keywords: Adipokine; Adiponectin; Leptin; Secretion; Trafficking; Adipocyte;

Microglia and astroglia prevent oxidative stress-induced neuronal cell death: Implications for aceruloplasminemia by Satoru Oshiro; Ken-ichi Kawamura; Chun Zhang; Toshio Sone; Masaki S. Morioka; Shin Kobayashi; Kazuyuki Nakajima (109-117).
We partially characterized the transferrin-independent iron uptake (Tf-IU) of neuronal and glial cells in the previous report. In the present study, we further examined a mechanism of which glial cells protect neuronal cells against iron stress using neuron–microglia (N–MG) and neuron–astrocyte (N–AS) co-cultures. When each solely purified cell was treated with iron citrate, cell death occurred in N and MG. However, AS proliferated under the same condition. Both N–MG and N–AS co-cultures were effective in resistance to excessive iron. The total and specific Tf-IU activities of N–MG co-cultures similar to those of N did not increase in a density-dependent manner. Contrarily, the total activity of AS was extremely high and the specific activity was extremely low as a result of proliferation. Regarding of effect of co-cultures on H2O2-induced cell death, N–MG co-cultures were less effective, but N–AS co-cultures were more effective in protecting N from the oxidative stress. These results suggest that N–MG co-cultures suppress the Tf-IU and N–AS co-cultures stimulate AS proliferation to protect neuronal cells. Brain cells from aceruloplasminemia with mutations in the ceruloplasmin gene take up iron by Tf-IU. Therefore, the different mechanisms of neuronal cell protection by MG and AS may explain the pathophysiological observations in the brains of patient with aceruloplasminemia.
Keywords: Microglial; Astrocyte; Neuronal cell death; Oxidative stress; Neurodegenerative disorders; Aceruloplasminemia;

TSPO over-expression increases motility, transmigration and proliferation properties of C6 rat glioma cells by Mariarosa Rechichi; Alessandra Salvetti; Beatrice Chelli; Barbara Costa; Eleonora Da Pozzo; Francesca Spinetti; Annalisa Lena; Monica Evangelista; Giuseppe Rainaldi; Claudia Martini; Vittorio Gremigni; Leonardo Rossi (118-125).
Gliomas are one of the most malignant cancers. The molecular bases regulating the onset of such tumors are still poorly understood. The translocator protein (TSPO), formerly known as the peripheral-type benzodiazepine receptor, is a mitochondrial permeability transition (MPT)-pore protein robustly expressed in gliomas and involved in the regulation of apoptosis and cell proliferation. TSPO expression levels have been correlated with tumor malignancy. Here we describe the production of C6 rat glioma cells engineered to over-express the TSPO protein with the aim of providing the first direct evidence of a correlation between TSPO expression level and glioma cell aggressiveness. We observed that TSPO potentiates proliferation, motility and transmigration capabilities as well as the ability to overcome contact-induced cell growth inhibition of glioma cells. On the whole, these data demonstrate that TSPO density influences metastatic potential of glioma cells. Since several data suggest that TSPO ligands may act as chemotherapeutic agents, in this paper we also demonstrate that TSPO ligand-induced cell death is dependent on TSPO density. These findings suggest that the use of TSPO ligands as chemotherapeutic agents could be effective on aggressive tumor cells with a high TSPO expression level.
Keywords: Peripheral-type benzodiazepine receptor; Glioma; Tumor invasiveness; Proliferation; Ligand-binding; Over-expression;