The Effect of Von Hippel-Lindau Gene Transfer on Human Vascular Smooth Muscle Cell Proliferation and Apoptosis

p53 gene therapy modulates signal transduction in the apoptotic and cell cycle pathways downregulating neointimal hyperplasia

PURPOSE

To investigate the molecular mechanisms that lead to inhibition of intimal hyperplasia (IH) following p53 gene therapy.

METHODS

In vivo p53 gene transfer to balloon injured rat carotid arteries was performed by utilizing adenovirus. The relationship between p53, p21, retinoblastoma protein (Rb), B-cell lymphoma 2 (Bcl-2), Bax, and Bcl-x was examined by immunohistochemistry. Expression of cyclin D1, Fas/CD95, and poly(ADP-ribose)polymerase (PARP) was determined.

RESULTS

Our data indicate increased expression of p53 in the nuclei of vascular smooth muscle cells (VSMCs) in the media (P < .01) compared with the controls. In the treated animals, Bax and Bcl-x, p21, and Rb were significantly upregulated (P < .01). Immunoreactivity to Bcl-2 was observed only in the neointima of untreated groups at 14 days. An increased presence of Fas and decreased expression of PARP was observed in the cytoplasm of the VSMCs of p53-treated animals.

CONCLUSIONS

P53 gene transfer activated a battery of downstream effector genes whose products are directly involved in cell cycle arrest, DNA repair, and apoptosis.

A cell-based assay for screening of antidotes to, and antivenom against Chironex fleckeri (box jellyfish) venom

INTRODUCTION

Chironex fleckeri is a large box jellyfish that has been labelled the 'most venomous animal' in the world. We have recently shown that the primary effect of C. fleckeri venom in vivo is cardiovascular collapse. This study utilised a cell-based assay to examine the effects of C. fleckeri venom on the proliferation of a rat aortic smooth muscle cell line. In addition, the ability of CSL box jellyfish antivenom and/or various potential treatment strategies to neutralise the effects of the venom was examined.

METHODS

A7r5 cells were cultured in media containing venom. The effect of CSL box jellyfish antivenom (5 U/mL), CSL polyvalent snake antivenom (5 U/mL), lanthanum (5 microM), MgSO(4) (50 mM), verapamil (5 microM) or felodipine (5 microM) was examined. Cell viability was determined using a Cell titer 96 AQueous One Solution cell proliferation assay.

RESULTS

Incubation of A7r5 cells with serially diluted venom (2-0.004 microg/mL) caused a concentration-dependent inhibition of cell proliferation with an IC(50) value of 0.056 microg/mL. This response was not affected by the absence of calcium or the presence of lanthanum in the media. Box jellyfish antivenom (5 U/mL) prevented the inhibition of cell proliferation caused by the venom. Verapamil (5 microM) had no significant effect on the inhibition. In contrast, felodipine (5 microM) or MgSO(4) (50 mM) potentiated the effects of the venom and partially negated the protective effect of the antivenom.

DISCUSSION

This study displayed the ability to utilise a cell-based assay to determine the effects of C. fleckeri venom on vascular cell viability. It showed that CSL box jellyfish can neutralise the effects of the venom but only if added prior to the venom. In addition, potential adjunct therapies verapamil, felodipine and MgSO(4) were found to be ineffective, with felodipine and MgSO(4) potentiating the detrimental effects of the venom.