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Hes1, a new target for interleukin 1beta in chondrocytes
Sebastien Ottaviani1, Khadija Tahiri, Aline Frazier
1Universite Paris Descartes; INSERM UMRS-747, Paris, France.
Objectives:
To investigate the effects of interleukin 1beta (IL1beta) treatment on the Notch1/Hes1 pathway in chondrocytes in vitro.
Methods:
Mouse articular chondrocytes in primary culture were challenged with IL1beta, alone or combined with Notch1 and IL1beta pathway inhibitors. Notch1 and Hes1 expressions were investigated by immunocytochemistry, western blot and real-time quantitative (q)PCR. IL1beta-responsive genes were assessed by real-time qPCR and a specific siRNA against Hes1 was used to identify Hes1 target genes.
Results:
Notch1 labelling remained nuclear and stable in intensity irrespective of treatment, suggesting a steady state activation of this pathway in our model. IL1beta transiently increased Hes1 mRNA (2.5-fold) and protein expression in treated versus naive chondrocytes. Hes1 mRNA level then decreased below control and its cyclic pattern of expression was lost. This was associated with nuclear translocation of the cytoplasmic Hes1 protein. IL1beta induced increase in Hes1 mRNA was transcriptional, occurred through nuclear factor (NF)kappaB activation and appeared to be associated with downregulation by its own protein. Hes1 induction was insensitive to the gamma-secretase inhibitor N-(N-(3,5-difluorophenacetyl)-l-alanyl)-S-phenylglycine t-butyl ester (DAPT), which suggested its independence from novel Notch1 activation. Hes1 expression was efficiently silenced by a specific siRNA. This experiment revealed that Hes1 did not mediate IL1beta-induced downregulation of Sox9, type II collagen and aggrecan transcription but mediated IL1beta induction of matrix metalloproteinase (MMP)13 and ADAM metallopeptidase with thrombospondin type 1 motif, 5 (ADAMTS5). The Hes1-related repressor Hey1 was expressed at a very low level and was not inducible by IL1beta.
Conclusion:
Hes1 is a novel IL1beta target gene in chondrocytes which influences a discrete subset of genes linked to cartilage matrix remodelling and/or degradation.
Insights
Interleukin 1beta (IL1beta) treatment in chondrocytes upregulates Hes1, a transcription factor involved in cartilage matrix remodeling. Hes1 influences matrix metalloproteinase expression but not cartilage matrix gene downregulation.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Interleukin 1beta (IL1beta) is a key inflammatory mediator in cartilage.
- The Notch1/Hes1 pathway plays a role in chondrocyte function and differentiation.
- Understanding IL1beta's impact on this pathway is crucial for cartilage biology.
Purpose of the Study:
- To investigate the effects of IL1beta on the Notch1/Hes1 pathway in chondrocytes.
- To elucidate the role of Hes1 in IL1beta-induced gene expression changes.
Main Methods:
- Primary mouse articular chondrocytes were treated with IL1beta.
- Notch1 and Hes1 expression analyzed via immunocytochemistry, Western blot, and qPCR.
- siRNA was used to silence Hes1 and identify its target genes.
Main Results:
- IL1beta treatment transiently increased Hes1 mRNA and protein expression in chondrocytes.
- Hes1 induction was NF-kappaB dependent and independent of Notch1 activation.
- Hes1 mediated IL1beta-induced expression of MMP13 and ADAMTS5, but not Sox9, type II collagen, or aggrecan.
Conclusions:
- Hes1 is a novel IL1beta target gene in chondrocytes.
- Hes1 influences specific genes related to cartilage matrix remodeling and degradation.
- This finding provides insight into the molecular mechanisms of IL1beta-driven cartilage changes.
