Excessive synthesis of matrix metalloproteinases in exocrine tissues of NOD mouse models for Sjogren's syndrome

Objective. Matrix metalloproteinases (MMP) and their substrates, components of the extracellular matrix, regulate environmental signals for cellular d ifferentiation and tissue function. Changes in the levels of these enzymes may influence cell survival as well as pathology involving ectopic apoptosi s. Using the non-obese diabetic (NOD) mouse model for Sjogren's syndrome, w e evaluated the synthesis and expression of MMP in the exocrine target tiss ues of autoimmunity. Methods. NOD, immunodeficient NOD-scid, and nondiabetic NOD.B10.H2(b) mice were evaluated for MMP activity in their saliva and exocrine gland lysates by gelatin zymography and reverse transcriptase-polymerase chain reaction ( RT-PCR). In addition, changes in protein content of saliva and gland lysate s were determined by specific Western blot and by enzymatic activity of amy lase and cysteine proteases. Mice continuously treated with the MMP inhibit or GM6001(R) were evaluated from 7 to 20 weeks of age for the contribution of MMP activity to development of these hallmark biochemical markers of Sjo gren's syndrome-like disease of NOD mice. Results. Gelatin zymography of whole saliva and gland lysates indicated the presence of increased proteolytic activity, corresponding to proteins with a molecular mass ranging from 50 to 95 kDa, in the saliva of older (> 20 w eeks of age) NOD mice as well as NOD.B10.H2(b) and NOD-scid mice compared t o BALB/c controls. Elevated steady state levels of mRNA transcripts for the gelatinases MMP-2 and MMP-9 were detected in total RNA extracted from paro tid and submandibular glands by RT-PCR. Despite prophylactic injection of t he broad spectrum MMP inhibitor GM6001(R) into mice beginning at 7 weeks of age and continuing to 20 weeks, development of the autoimmune exocrinopath y was neither stopped nor retarded. Conclusion, These observations suggest that excessive MMP activity is assoc iated with autoimmune Sjogren's syndrome-like disease in NOD mice. However, a possible contribution by increased MMP activity in initiation and progre ssion of this autoimmune disease is yet to be elucidated.