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Brief Report: Stress‐Inducible Nuclear Protein 1 Regulates Matrix Metalloproteinase 13 Expression in Human Articular Chondrocytes
Author(s) -
Yammani Raghunatha R.,
Loeser Richard F.
Publication year - 2014
Publication title -
arthritis and rheumatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.106
H-Index - 314
eISSN - 2326-5205
pISSN - 2326-5191
DOI - 10.1002/art.38391
Subject(s) - thapsigargin , gene knockdown , cartilage , messenger rna , small interfering rna , chemistry , immunostaining , endoplasmic reticulum , matrix metalloproteinase , transfection , gene expression , chondrocyte , microbiology and biotechnology , matrix metalloproteinase 3 , andrology , medicine , endocrinology , immunohistochemistry , biology , gene , anatomy , biochemistry
Objective Nuclear protein 1 (Nupr1) is a stress‐inducible protein that is involved in gene transcription. The present study was undertaken to determine whether chondrocytes express Nupr1 and whether Nupr1 regulates matrix metalloproteinase 13 (MMP‐13) expression. Methods Paraffin‐embedded cartilage sections from normal human and osteoarthritic (OA) cartilage were immunostained using anti‐Nupr1 antibody. To measure Nupr1 expression, total RNA was isolated from joint tissue obtained 8 weeks after surgery from young (12‐week‐old) and older (12‐month‐old) mice that underwent destabilization of the medial meniscus (DMM) to induce OA. Human chondrocytes were stimulated with 1–10 ng/ml interleukin‐1β (IL‐1β), 25 μ M tert ‐butyl‐hydroperoxide (tBHP), or 2 μ M thapsigargin, and Nupr1 expression was analyzed by quantitative polymerase chain reaction. In addition, chondrocytes were transfected with small interfering RNA to knock down Nupr1 expression and then stimulated overnight with IL‐1β. After incubation, the conditioned medium was collected and MMP levels measured. Results Increased Nupr1 immunostaining was noted in human OA cartilage compared to normal cartilage. Expression was also increased in joint tissue from 12‐month‐old mice that underwent DMM surgery compared to sham‐operated controls. Stimulation of chondrocytes with IL‐1β induced a 2‐fold increase in Nupr1 messenger RNA (mRNA) within 1 hour, with the increase peaking to 4‐fold at 6 hours. Treatment of chondrocytes with tBHP to induce oxidative stress increased Nupr1 mRNA expression by >2‐fold; treatment with thapsigargin to induce endoplasmic reticulum stress did not produce a similar effect. Knockdown of Nupr1 inhibited IL‐1β–mediated induction of MMP‐13. Conclusion Nupr1 is expressed in cartilage, and its levels are increased in OA. Nupr1 expression is required for IL‐1β–mediated expression of MMP‐13. These findings provide evidence of a novel pathway for regulation of IL‐1β–mediated production of MMPs in chondrocytes.