Thromboxane A2 modulates migration, proliferation, and differentiation of adipose tissue-derived mesenchymal stem cells

Prostanoid metabolites are key mediators in inflammatory responses, and accumulating evidence suggests that mesenchymal stem cells (MSCs) can be recruited to injured or inflamed tissues. In the present study, we investigated whether prostanoid metabolites can regulate migration, proliferation, and differentiation potentials of MSCs. We demonstrated herein that the stable thromboxane A2 (TxA2) mimetic U46619 strongly stimulated migration and proliferation of human adipose tissue-derived MSCs (hADSCs). Furthermore, U46619 treatment increased expression of alpha-smooth muscle actin (alpha-SMA), a smooth muscle marker, in hADSCs, suggesting differentiation of hADSCs into smooth muscle-like cells. U46619 activated ERK and p38 MAPK, and pretreatment of the cells with the MEK inhibitor U0126 or the p38 MAPK inhibitor SB202190 abrogated the U46619-induced migration, proliferation, and alpha-SMA expression. These results suggest that TxA2 plays a key role in the migration, proliferation, and differentiation of hADSCs into smooth muscle-like cells through signaling mechanisms involving ERK and p38 MAPK.

Emodin ameliorates high-glucose induced mesangial p38 over-activation and hypocontractility via activation of PPARgamma

Early stage diabetic nephropathy is characterized by elevated glomerular filtration. Recent studies have identified high-glucose induced p38 MAPK (p38) over-activation in mesangial cells. Mesangial hypocontractility is the major underlying mechanism, however, no ameliorating agents are currently available. We investigated the protective effects of emodin on high-glucose induced mesangial cell hypocontractility. Mesangial cells were cultured under normal (5.6 mM) and high glucose (30 mM) conditions. Emodin was administrated at doses of 50 mg/l and 100 mg/l. Angiotension II stimulated cell surface reductions were measured to evaluate cell contractility. p38 activity was detected using Western blotting. To further explore the possible mechanism of emodin, expression of the peroxisome proliferator-activated receptor gamma (PPARgamma) was measured and its specific inhibitor, gw9662, was administrated. Our results showed: (1) high-glucose resulted in a 280% increase in p38 activity associated with significant impairment of mesangial contractility; (2) emodin treatment dose-dependently inhibited high-glucose induced p38 over-activation (a 40% decrease for 50 mg/l emodin and a 73% decrease for 100 mg/l emodin), and mesangial hypocontractility was ameriolated by emodin; (3) both the PPARgamma mRNA and protein levels were elevated after emodin treatment; (4) inhibition of PPARgamma using gw9662 effectively blocked the ameliorating effects of emodin on high-glucose induced p38 over-activation and mesangial hypocontractility. Emodin effectively ameliorated p38 over-activation and hypocontractility in high-glucose induced mesangial cells, possibly via activation of PPARgamma.

Alternagin-C, a disintegrin-like protein from the venom of Bothrops alternatus, modulates alpha2ß1 integrin-mediated cell adhesion, migration and proliferation

The alpha2ß1 integrin is a major collagen receptor that plays an essential role in the adhesion of normal and tumor cells to the extracellular matrix. Alternagin-C (ALT-C), a disintegrin-like protein purified from the venom of the Brazilian snake Bothrops alternatus, competitively interacts with the alpha2ß1 integrin, thereby inhibiting collagen binding. When immobilized in plate wells, ALT-C supports the adhesion of fibroblasts as well as of human vein endothelial cells (HUVEC) and does not detach cells previously bound to collagen I. ALT-C is a strong inducer of HUVEC proliferation in vitro. Gene expression analysis was done using an Affimetrix HU-95A probe array with probe sets of 10,000 human genes. In human fibroblasts growing on collagen-coated plates, ALT-C up-regulates the expression of several growth factors including vascular endothelial growth factor, as well as some cell cycle control genes. Up-regulation of the vascular endothelial growth factor gene and other growth factors could explain the positive effect on HUVEC proliferation. ALT-C also strongly activates protein kinase B phosphorylation, a signaling event involved in endothelial cell survival and angiogenesis. In human neutrophils, ALT-C has a potent chemotactic effect modulated by the intracellular signaling cascade characteristic of integrin-activated pathways. Thus, ALT-C acts as a survival factor, promoting adhesion, migration and endothelial cell proliferation after binding to alpha2ß1 integrin on the cell surface. The biological activities of ALT-C may be helpful as a therapeutic strategy in tissue regeneration as well as in the design of new therapeutic agents targeting alpha2ß1 integrin.

Regeneraçäo de Células após Ototoxicidade com Aminoglicosídeo na Cóclea de Aves / Hair Cell Regeneration in the Avian Cochlea after Ototoxicity with Aminoglycoside

Introduçäo: As células ciliadas podem ser lesada por inúmeros agentes, incluindo os antibióticos aminoglicosídeos. Na cóclea das aves, a perda das células ciliadas pode ser reposta por regeneraçäo. Objetivos: Os objetivos da pesquisa foram estudar o processo de regeneraçäo em aves e a progressäo temporal das lesöes provocadas pela gentamicina. Material e método: No estudo, foi administrada gentamicina em dose única subcutânea de 125 e 250 mg/kg respectivamente, em um e outro grupos de pintos de três dias. As cócleas foram processadas, para anáIise em microscopia eletrônica de varredura, no 1§, 3§, 5§ e 20§ dias após a injeçäo. A sequência celular de degeneraçäo e regeneraçäo foi estudada. No 20§ dia, a maior parte da área cóclear lesada havia sido reposta por células ciliadas e de suporte regeneradas. Estereocílios e microvilos foram observados na superfície apical das células ciliadas regeneradas

Lessons from tumor and immunocompetent cells. The quantitative engagement of ligand-receptor interactions modulates stop-and-go behavior as well as proliferation

The four main cell functions, proliferation, apoptosis, differentiation and migration, are tightly regulated by external signals that initiate intracellular signal transduction pathways and determine the cellular behaviour. The concentration and composition of such external signals are at least important for the decision of cells as to which function has to be executed. Interleukin-8 is a well known inducing signal for neutrophil granulocyte migration, while the epidermal growth factor is an inducing signal for breast carcinoma cell migration. Depending on the concentrations of interleukin-8, the neutrophil granulocytes are capable of migration. However, at high concentration of interleukin-8 the migratory activity of each single cell is reduced, indicating that high concentrations of the chemokine inhibit migration and promote the performance of other cell functions. Concerning breast carcinoma cells, the epidermal growth factor is not only an inducer of migration but also an inhibitor of proliferation. These two examples provide evidence for a dose dependent action of external signals for several cell functions in parallel. This versatility of the effects of one ligand might be based on several intracellular signal transduction pathways that are turned on. For the dose-dependent differences of the effect of interleukin-8 we propose a two wheel model of an inositolphosphate-mediated, ATP-independent release of calcium from intracellular stores and a cyclic AMP-mediated, ATP-dependent uptake of calcium into the endoplasmatic reticulum.

Participaçäo de fatores de crescimento na regeneraçäo celular pós-necrose tubular aguda / Participation of growth factors in cell regeneration after acute tubular necrosis

A recuperaçäo da funçao renal após a necrose tubular aguda (NTA) depende da proliferaçäo de células e da substituiçäo de células necróticas e lesadas por células recém-formadas. Várias linhas de evidências indicam que o EGF (Epidermal Growth Factor), IGF-I (Insulin Growth Factor-I) e o HGF (Hepatocyte Growth Factor) devem participar da regeneraçäo célular pós-NTA: a) o EGF e o HGF säo capazes de desencadear potentes estímulos mitóticos em células de túbulos proximais; b) receptores para EGF e IGF-I estäo presentes em células de túbulos proximais; c) após a NTA ocorre um aumento dos receptores renais para IGF-I e EGF; d) a administraçäo de EGF, IGF-I ou HGF a ratos com NTA aumenta a velocidade de regeneraçäo celular e de recuperaçäo da funçao renal e e) o IGF-I é capaz de induzir a proliferaçäo de células renais e além disso tem efeitos no anabolismo celular e na hemodinâmica renal (aumenta o fluxo plasmático renal e a taxa de filtraçao glomerular). Tem sido proposto por vários autores o uso terapêutico de um ou mais desse fatores em pacientes com NTA. Contudo, consideramos necessária a realizaçäo de maior número de estudos para melhor entendimento dos mecanismos de açäo desses polipeptideos e avaliaçäo de seus efeitos na NTA.