Christiano M.V. Barbosa

Pre-clinical antitumour evaluation of Biphosphinic Palladacycle Complex in human leukaemia cells

Previous studies reported by our group have introduced a new antitumoural drug called Biphosphinic Palladacycle Complex (BPC). In this paper we show that BPC causes apoptosis in leukaemia cells (HL60 and Jurkat), but not in normal human lymphocytes. IC(50) values obtained for both cell lines using the MTT and trypan blue exclusion assays 5h after BPC treatment were lower than 8.0 microM. Using metachromatic fluorophore, acridine orange, we observed that BPC elicited lysosomal rupture of leukaemic cells. Furthermore, BPC triggered caspase-3 and caspase-6 activation and apoptosis in cell lines, inducing chromatin condensation, apoptotic bodies, and DNA fragmentation. Interestingly, the lysosomal cathepsin B inhibitor CA074 markedly decreased BPC-induced caspase-3 and caspase-6 activation as well as cell death. Lysosomal BPC-induced membrane destabilisation was not dependent on reactive oxygen species generation, which was consistent with the absence of cellular HL60 and Jurkat membrane lipid peroxidation. We conclude that, following BPC treatment, lysosomal membrane rupture precedes cell death and the apoptotic signalling pathway is initiated by the release of cathepsin B in the cytoplasm of leukaemia cells. As no toxic effects for human lymphocytes were observed, we suggest that BPC is more selective for transformed cells, mainly due to their exacerbated lysosome expression.

Requirement for PLCγ2 in IL‐3 and GM‐CSF‐stimulated MEK/ERK phosphorylation in murine and human hematopoietic stem/progenitor cells

Even though the involvement of intracellular Ca2+ (

Autophagy inhibited Ehrlich ascitic tumor cells apoptosis induced by the nitrostyrene derivative compounds: Relationship with cytosolic calcium mobilization

{\rm Ca}_{{\rm i}}^{{\rm 2 + }}

α‐Tocopherol induces hematopoietic stem/progenitor cell expansion and ERK1/2‐mediated differentiation

) in hematopoiesis has been previously demonstrated, the relationship between

Chlorella vulgaris restores bone marrow cellularity and cytokine production in lead-exposed mice

{\rm Ca}_{{\rm i}}^{{\rm 2 + }}

Calcium signaling as a regulator of hematopoiesis.

signaling and cytokine‐induced intracellular pathways remains poorly understood. Herein, the molecular mechanisms integrating Ca2+ signaling with the extracellular signal‐regulated kinase 1/2 (ERK1/2) pathway in primary murine and human hematopoietic stem/progenitor cells stimulated by IL‐3 and GM‐CSF were studied. Our results demonstrated that IL‐3 and GM‐CSF stimulation induced increased inositol 1,4,5‐trisphosphate (IP3) levels and

PLCγ2 and PKC are important to myeloid lineage commitment triggered by M-SCF and G-CSF.

{\rm Ca}_{{\rm i}}^{{\rm 2 + }}

Myelopoiesis modulation by ACE hyperfunction in kinin B1 receptor knockout mice: Relationship with AcSDKP levels

release in murine and human hematopoietic stem/progenitor cells. In addition,

Chlorella vulgaris treatment ameliorates the suppressive effects of single and repeated stressors on hematopoiesis

{\rm Ca}_{{\rm i}}^{{\rm 2 + }}

Hematopoietic stem cell expansion caused by a synthetic fragment of leptin

signaling inhibitors, such as inositol 1,4,5‐trisphosphate receptor antagonist (2‐APB), PKC inhibitor (GF109203), and CaMKII inhibitor (KN‐62), blocked phosphorylation of MEK activated by IL‐3 and GM‐CSF, suggesting the participation of Ca2+‐dependent kinases in MEK activation. In addition, we identify phospholipase Cγ2 (PLCγ2) as a PLCγ responsible for the induction of Ca2+ release by IL‐3 and GM‐CSF in hematopoietic stem/progenitor cells. Furthermore, the PLCγ inhibitor U73122 significantly reduced the numbers of granulocyte‐macrophage colony‐forming units after cytokine stimulation. Similar results were obtained in both murine and human hematopoietic stem/progenitor cells. Taken together, these data indicate a role for PLCγ2 and Ca2+ signaling through the modulation of MEK in both murine and human hematopoietic stem/progenitor cells. J. Cell. Physiol. 226: 1780–1792, 2011.