Long-term cultivation of a neuroblastoma cell line in medium with reduced serum content as a model system for neuronal aging?

Metformin protects cardiomyocyte from doxorubicin induced cytotoxicity through an AMP-activated protein kinase dependent signaling pathway: an in vitro study

Doxorubicin (Dox) is one of the most widely used antitumor drugs, but its cumulative cardiotoxicity have been major concerns in cancer therapeutic practice for decades. Recent studies established that metformin (Met), an oral anti-diabetic drug, provides protective effects in Dox-induced cardiotoxicity. Met has been shown to increase fatty acid oxidation, an effect mediated by AMP activated protein kinase (AMPK). Here we delineate the intracellular signaling factors involved in Met mediated protection against Dox-induced cardiotoxicity in the H9c2 cardiomyoblast cell line. Treatment with low dose Met (0.1 mM) increased cell viabilities and Ki-67 expressions while decreasing LDH leakages, ROS generations and [Ca2+]i. The protective effect was reversed by a co-treatment with compound-C, an AMPK specific inhibitor, or by an over expression of a dominant-negative AMPKα cDNA. Inhibition of PKA with H89 or a suppression of Src kinase by a small hairpin siRNA also abrogated the protective effect of the low dose Met. Whereas, with a higher dose of Met (1.0 mM), the protective effects were abolished regardless of the enhanced AMPK, PKA/CREB1 and Src kinase activity. In high dose Met treated cells, expression of platelet-derived growth factor receptor (PDGFR) was significantly suppressed. Furthermore, the protective effect of low dose Met was totally reversed by co-treatment with AG1296, a PDGFR specific antagonist. These data provide in vitro evidence supporting a signaling cascade by which low dose Met exerts protective effects against Dox via sequential involvement of AMPK, PKA/CREB1, Src and PDGFR. Whereas high dose Met reverses the effect by suppressing PDGFR expression.

High ambient glucose induces angiotensin-independent AT-1 receptor activation, leading to increases in proliferation and extracellular matrix accumulation in MES-13 mesangial cells

Diabetic nephropathy is associated with mesangial ECM (extracellular matrix) accumulation. We have shown that AT-1R [Ang II (angiotensin II) type I receptor] signalling induces ECM proteins via transactivation of PI3K (phosphoinositide 3-kinase) in mesangial cells. In the present study, we examined the mechanisms underlying the effect of high ambient glucose on cell proliferation and ECM expansion in a mesangial context. High glucose induced increases in PI3K activity, proliferation and ECM accumulation in mesangial cells. These effects were abrogated by losartan, an AT-1R antagonist, but not by [Sar1,Thr8]-Ang II (Sar is sarcosine), an inactive analogue of Ang II, or by a neutralizing antibody against Ang I/II. Overexpression of a constitutively active PI3Kα or AT-1R alone was sufficient to induce similar changes by high glucose. In contrast, overexpression of an inactive AT-1R lowered the basal levels and rendered the cells non-responsive to high glucose. Moreover, cells overexpressing wild-type AT-1R had enhanced sensitivity to acute Ang II stimulation. These cells, however, did not respond to conditioned medium obtained from mesangial cells cultured in high glucose. We further demonstrated that iAng (intracellular Ang II) can be induced by high glucose but only under certain conditions. Efficient suppression of iAng by short hairpin RNA against angiotensinogen, however, did not affect high glucose-induced effects on MES-13 cells. These results suggest that high ambient glucose induces activation of AT-1R in an Ang II-independent manner to transactivate PI3K, resulting in proliferation and ECM accumulation in mesangial cells.

Hydroxyl free radicals induce cell differentiation in SK-N-MC neuroblastoma cells

The SK-N-MC cell line is frequently used as a model of neuronal differentiation induced by 5-bromodeoxyuridine (BrdU). In this study, the differentiation properties of this cell line were investigated under hydroxyl free radical generation, and compared to BrdU treatment. Hydroxyl free radicals were generated in the cultures by the Fenton reaction, i.e. by simultaneous addition of ADP-Fe2+ complex and H2O2. Microscopic morphological signs, as well as the acetylcholinesterase and ganglioside sialidase activities were considered as markers of neuronal differentiation of this cholinergic neuroblastoma cell line. Apart from the altered morphological appearance, the marker enzymes displayed significant increases after both types of intervention. We suggest that hydroxyl free radicals can induce in vitro cell differentiation. They apparently play a more complex role in cell physiology than simply causing oxidative damage.