JQuery :: Accordion To List All Email Received / Sent

I'm using the jquery accordion in order to list all email received/sent. The header (h3+a) shows the object, the content (div) is the mail text.

HTML accordion :
<div id="accordion"><div>
<h3><a href="#">object 1</a></h3>
<div>mail 1 text</div>
</div><div>
<h3><a href="#">object 2</a></h3>
<div>mail 2 text</div>
</div>
<div>
<h3><a href="#">object 3</a></h3>
<div>mail 3 text</div>
</div>
</div>

Accordion script function:
$(function() {
$( "#accordion" ).accordion({
autoHeight: false,
header: "h3",
navigation: true
});
});

I would like to request my SQL database only when i clic on the header of a mail, and avoid to preload all the mails. The other problem, much important in my case, is to mark the mail "read" or "unread". There is a column in the SQL database for this. So, the mail needs to change to "read" state when I click on his accordion's header. Before using accordion, I was using simple link which reloads all the page. I've no problem with PHP/SQL, but I'm not so good in javascript/jquery, or ajax...

SQL request (simplified) :
$sql = "SELECT mail_object, mail_text FROM table_mail ";
$req = mysql_query($sql);
SQL update read-state (simplified) :
$sql_2 = "UPDATE table_mail SET mail_read=1 ";
$req_2 = mysql_query($sql_2);

So, is there any way to execute this code when I click on a header? After that, I'll asking you how to change header style to differentiate read/unread mail (in bold for example, or change background image/color).