Interleukin 1 beta enhances the response of rabbit synovial fibroblasts in vitro to dexamethasone injury: implication for the role of increased nuclear hypersensitive sites and the number of dexamethasone receptors.
OBJECTIVE
As a model system to understand the efficacy of patients with glucocorticoid (GC) treatment of joint inflammation of rheumatoid arthritis, we stimulated confluent rabbit synovial fibroblasts in culture with interleukin 1 beta (IL-1 beta) and studied the effects of dexamethasone (Dex).


METHODS
Twenty-four h after IL stimulation Dex was added and the response of cells to Dex was estimated by [3H]thymidine uptake, cell count and lactate dehydrogenase release. Cellular and nuclear binding of [3H] Dex as well as the DNase sensitivity of isolated nuclei were estimated.


RESULTS
Dex strongly inhibited the [3H]thymidine uptake by the stimulated cells in a dose dependent manner with Ki of lower than 10(-12) M, whereas it only slightly inhibited the unstimulated cells. With stimulation the sensitivity of cells increased 10-fold as estimated by lactate dehydrogenase release and 85-fold by counting the final cell density. We found also a 5-fold increase in the DNase I hypersensitive sites in the nuclei and a 2 to 3-fold increase in the cellular as well as the nuclear Dex binding sites following stimulation.


CONCLUSIONS
In addition to the well documented inhibition of degradative enzyme production by the stimulated synovium, the efficacy of GC treatment of patients could be explained also on the basis of the sensitization of stimulated synovium to the GC mediated injury.
Robert Koch-Institute, Biochemistry Department, Berlin, Germany.
J
J
Hoshino
G
G
Beckmann
J
J
Huser
H
H
Kröger
D000818:Animals; D001172:Arthritis, Rheumatoid / Q000188:drug therapy / Q000378:metabolism; D002452:Cell Count; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D017364:Collagenases / Q000096:biosynthesis; D004247:DNA / Q000378:metabolism; D003850:Deoxyribonuclease I; D003907:Dexamethasone / Q000008:administration & dosage* / Q000378:metabolism / Q000633:toxicity; D004357:Drug Synergism; D004790:Enzyme Induction / Q000187:drug effects; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D066298:In Vitro Techniques; D007375:Interleukin-1 / Q000008:administration & dosage*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D011817:Rabbits; D011965:Receptors, Glucocorticoid / Q000187:drug effects / Q000378:metabolism; D013583:Synovial Membrane / Q000166:cytology / Q000187:drug effects* / Q000293:injuries; D013936:Thymidine / Q000378:metabolism
D007375:Interleukin-1; D011965:Receptors, Glucocorticoid; C028697:dexamethasone receptor; D003907:Dexamethasone; D004247:DNA; D007770:L-Lactate Dehydrogenase; D003850:Deoxyribonuclease I; D017364:Collagenases; D013936:Thymidine