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Pyrrolidine dithiocarbamate differentially affects interleukin 1 beta- and cAMP-induced nitric oxide synthase
W Eberhardt1, D Kunz, J Pfeilschifter
1Department of Pharmacology, University of Basel, Switzerland.
Abstract:
Inducible nitric oxide synthase (NOS) is expressed in renal mesangial cells in response to two principal classes of activating signals that interact in a synergistic fashion. These two groups of activators comprise inflammatory cytokines such as interleukin 1 (IL-1) or tumour necrosis factor alpha and agents that elevate cellular levels of cAMP. We have used pyrrolidine dithiocarbamate (PDTC), a potent inhibitor of nuclear factor kappa B (NF kappa B), to determine its role in IL-1 beta- and cAMP-triggered NOS expression. Micromolar amounts of PDTC suppress IL-1 beta-, but not cAMP-stimulated nitrite production, the stable end product of NO formation in mesangial cells. Furthermore, PDTC completely inhibited the increase of NOS mRNA in response to IL-1 beta, while only marginally affecting cAMP-induced NOS mRNA levels. Our data suggest that NF kappa B activation is an essential component of the IL-1 beta signalling pathway responsible for NOS gene activation and that cAMP triggers a separate signalling cascade not involving NF kappa B. These observations may provide a basis for the synergistic stimulation of NOS expression by cytokines and cAMP in mesangial cells.
Insights
Nuclear factor kappa B (NF kappa B) mediates interleukin-1 beta (IL-1 beta)-induced nitric oxide synthase (NOS) expression in kidney cells. Cyclic AMP (cAMP) stimulates NOS via a separate pathway not involving NF kappa B.
Area of Science:
- Nephrology
- Molecular Biology
- Immunology
Background:
- Inducible nitric oxide synthase (iNOS) expression in renal mesangial cells is activated by inflammatory cytokines and agents that increase cyclic adenosine monophosphate (cAMP).
- These two signaling pathways interact synergistically to enhance iNOS expression.
Purpose of the Study:
- To investigate the role of nuclear factor kappa B (NF kappa B) in the interleukin-1 beta (IL-1 beta)- and cAMP-stimulated expression of iNOS in mesangial cells.
- To elucidate the distinct signaling cascades involved in cytokine- and cAMP-mediated iNOS induction.
Main Methods:
- Utilized pyrrolidine dithiocarbamate (PDTC), a specific inhibitor of NF kappa B activation.
- Measured nitrite production (a marker of nitric oxide formation) and iNOS mRNA levels in mesangial cells stimulated with IL-1 beta and/or cAMP in the presence or absence of PDTC.
Main Results:
- PDTC significantly suppressed IL-1 beta-induced nitrite production and iNOS mRNA levels.
- PDTC had minimal effect on cAMP-stimulated nitrite production and iNOS mRNA levels.
- NF kappa B activation is crucial for IL-1 beta-triggered iNOS gene expression.
Conclusions:
- NF kappa B is a key mediator in the IL-1 beta signaling pathway leading to iNOS expression in renal mesangial cells.
- cAMP activates iNOS through a distinct signaling cascade that does not involve NF kappa B.
- These findings explain the synergistic effect of cytokines and cAMP on iNOS expression.