il\VOLVEMENT OF RETII\OIC ACID II{ - MSpace at the University of ...
il\VOLVEMENT OF RETII\OIC ACID II{ - MSpace at the University of ...
il\VOLVEMENT OF RETII\OIC ACID II{ - MSpace at the University of ...
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and development <strong>of</strong> heart blocks. The changes in <strong>the</strong> conductivity were <strong>at</strong>tributed to <strong>the</strong><br />
down-regul<strong>at</strong>ion and redistribution <strong>of</strong> gap junction protein Cx40 and <strong>the</strong> disruption <strong>of</strong> <strong>the</strong><br />
expression <strong>of</strong> intercal<strong>at</strong>ed discs proteins- p-c<strong>at</strong>enin and N-cadherin (van Veen et al.<br />
2002).<br />
Thus, a number <strong>of</strong> studies indic<strong>at</strong>e <strong>the</strong> existence <strong>of</strong> multitude <strong>of</strong> regul<strong>at</strong>ory<br />
function executed by retinoic acid on <strong>the</strong> heart tissue. However, current research has just<br />
touched <strong>the</strong> tip <strong>of</strong> <strong>the</strong> iceberg and retinoic acid function may prove to be essential in <strong>the</strong><br />
multitude <strong>of</strong> physiological and p<strong>at</strong>hological processes not only during fetal development,<br />
but also during <strong>the</strong> adult life.<br />
IV.e.Retinoic acid and apoptosis<br />
As previously mentioned, retinoic acid is involved in <strong>the</strong> regul<strong>at</strong>ion <strong>of</strong> <strong>the</strong><br />
expression <strong>of</strong> a number <strong>of</strong> genes. Some <strong>of</strong> <strong>the</strong> genes are involved in <strong>the</strong> prevention or<br />
execution <strong>of</strong> apoptosis. However, <strong>the</strong> exact role <strong>of</strong> retinoic acid in apoptosis is still<br />
controversial. Fur<strong>the</strong>rmore, it is dependent on <strong>the</strong> cell type, cell m<strong>at</strong>urity, specificity <strong>of</strong><br />
retinoic acid isomers and presence or <strong>the</strong> absence <strong>of</strong> o<strong>the</strong>r stimuli (Nugy et al. 1998)<br />
(Ashwell 1998). In fact, it is reported th<strong>at</strong> <strong>the</strong> retinoic acid regul<strong>at</strong>es <strong>the</strong> expression <strong>of</strong><br />
programmed cells de<strong>at</strong>h, inducing <strong>the</strong> apoptosis in certain cell types (Martin et al. 1990),<br />
while inhibiting it in <strong>the</strong> o<strong>the</strong>rs (Yang et al. 1993), Apoptosis regul<strong>at</strong>ing characteristics <strong>of</strong><br />
retinoic acid are utilized in <strong>the</strong>rapy <strong>of</strong> high-prolifer<strong>at</strong>ive, pre malignant and malignant<br />
diseases such as acute promyelocytic leukemia (APL) (Jimenez-Lara et al. 2004), T-cell<br />
l1'rnphoma (Zhang and Duvic 2003), Kaposi's sarcoma (Aboulafia et al. 2003) and<br />
variety <strong>of</strong> skin cancers (Niles 2002). The ongoing studies indic<strong>at</strong>e <strong>the</strong> potential usage <strong>of</strong><br />
retinoic acid in <strong>the</strong> tre<strong>at</strong>ment <strong>of</strong> squamous cell carcinoma, ovarian carcinoma,<br />
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