J Korean Surg Soc.  2002 Jan;62(1):8-17.

Mycophenolic Acid Induced Apoptotic Signal Transduction in Molt-4 T-cells

• Choi SJ
• Chung SY
• Kim SK

Abstract

PURPOSE: Mycophenolic acid (MPA), a selective inhibitor of inosine monophosphate dehydrogenase (IMPDH), is the active metabolite of the immunosuppressive drug, mycophenolate mofetil (MMF). MMF is used to prevent an immune- mediate rejection response following organ transplantation via the inhibition of the IMPDH and GTP biosynthesis pathway. This study was designed to elucidate the mechanism by which MPA exerts its cytotoxic effect on human T lymphocytic and monocytic cell lines.
METHODS
MOLT-4 and U937 cell lines were treated with MPA. Cell viability, expression of Bcl2 family proteins and Fas/Fas-L, effects of antioxidants and intracellular Ca2+ regulating agents and apoptosis were measured using a variety of microscopic and biochemical techniques.
RESULTS
MPA induced the death of U937 and MOLT-4 cells in dose and time dependent manners, which was revealed an apoptosis with a characteristic ladder pattern of DNA fragmentation. In addition, BAPTA/AM, an intracellular Ca2+ chelator protected MOLT-4 cells from MPA treated apoptosis, although it did not have an additive with thapsigargin, and increases cytosolic Ca2+ stores. However, antioxidants including reduced glutathione (GSH) and N-acetyl-L-cysteine (NAC) did not inhibit the apoptosis of cells by MPA. Furthermore, guanosine suppressed MPA induced apoptosis of MOLT-4 lymphocytes, although adenosine did not. MPA also increased the catalytic activity of caspase family cysteine proteases including caspase-8, 9 and 3 proteases in MOLT-4 cells. Sequential activation indicated that the cleavage of caspase-8 and 9 precedes those of caspase-3.
CONCLUSION
The results suggest that MPA induces the apoptotic death of MOLT-4 lymphocytes via the activations of caspase family proteases and the depletion of GTP.

Keyword

Mycophenolic acid; Apoptosis; Bcl2 family proteins; Caspase family cysteine proteases; GTP

MeSH Terms

Acetylcysteine
Adenosine
Antioxidants
Apoptosis
Caspase 3
Caspase 8
Cell Line
Cell Survival
Cysteine Proteases
Cytosol
DNA Fragmentation
Glutathione
Guanosine
Guanosine Triphosphate
Humans
Inosine Monophosphate
Lymphocytes
Mycophenolic Acid*
Organ Transplantation
Oxidoreductases
Peptide Hydrolases
Signal Transduction*
T-Lymphocytes*
Thapsigargin
Transplants
U937 Cells
Acetylcysteine
Adenosine
Antioxidants
Caspase 3
Caspase 8
Cysteine Proteases
Glutathione
Guanosine
Guanosine Triphosphate
Inosine Monophosphate
Mycophenolic Acid
Oxidoreductases
Peptide Hydrolases
Thapsigargin