The destructive action of IL-1alpha and IL-1beta in IDDM is a multistage process: evidence and confirmation by apoptotic studies, induction of intermediates and electron microscopy.

Using the rat beta-cell RIN-5AH insulinoma line as a means for studying insulin-dependent diabetes mellitus (IDDM), it is shown that interleukin-1 (IL-1) induces beta-cell damage initiated by early apoptotic signals. This action is demonstrated by DNA fragmentation, as assessed by specific BrdU labeling, surface expression of Fas and nitric oxide (NO) production. In addition, the interplay between NO and Fas is shown, while scanning electron microscopy (SEM) confirms apoptosis by revealing the degree and type of cellular damage which, in the case of IL-1alpha, can be reversed by an inhibitor to NO synthesis. Apoptosis is also reconfirmed by transmission electron microscopy (TEM) by observing condensed nuclear chromatin after IL-1 exposure. Thus, treatment of insulinoma cells with IL-1alpha and IL-1beta seems to initiate a number of signals, including PKC activation as published previously, that ultimately lead to beta-cell destruction. Each IL-1 isoform, however, definitely follows a different pathway of action.