EXPERIMENTAL AND BASIC RESEARCH STUDY
Regulation of hypoxia-inducible factor-1α and related genes in equine digital lamellae and in cultured keratinocytes
Article first published online: 22 JUL 2013
© 2013 EVJ Ltd
Equine Veterinary Journal
Volume 46, Issue 2, pages 203–209, March 2014
How to Cite
Pawlak, E. A., Geor, R. J., Watts, M. R., Black, S. J., Johnson, P. J. and Belknap, J. K. (2014), Regulation of hypoxia-inducible factor-1α and related genes in equine digital lamellae and in cultured keratinocytes. Equine Veterinary Journal, 46: 203–209. doi: 10.1111/evj.12092
- Issue published online: 18 FEB 2014
- Article first published online: 22 JUL 2013
- Accepted manuscript online: 18 APR 2013 04:33AM EST
- Manuscript Accepted: 7 APR 2013
- Manuscript Received: 13 NOV 2012
- Morris Animal Foundation. Grant Number: D02EQ-017
- hypoxia inducible factor-1α;
- digital lamellae
Reasons for performing study
Hypoxia-inducible factor-1α (HIF-1A) is an important protein in the regulation/induction of many genes in the cellular and tissue response to hypoxia and a central mediator in inflammatory signalling. As both hypoxia and inflammatory events are purported to occur in the lamellar epidermis in sepsis-related laminitis in the equid, HIF-1A may play a central role in this disease process.
To assess the regulation of HIF-1A and HIF-1A-related genes in the equine keratinocyte in vitro and in the lamellar tissue of horses with sepsis-related laminitis.
In vivo and in vitro experiments.
Real-time quantitative PCR (RT-qPCR) and immunoblotting were performed to assess the mRNA and protein concentrations of HIF-1A and the mRNA concentrations of HIF-1A-related genes in cultured equine keratinocytes and in lamellar samples from black walnut extract (BWE)- and carbohydrate overload (CHO)-induced laminitis. Hypoxia-inducible factor-1α was further localised via indirect immunofluorescence in frozen lamellar tissue sections.
Hypoxia-inducible factor-1α appears to be regulated primarily at the post transcriptional level in the cultured equine keratinocyte, resulting in increased HIF-1A in response to hypoxia but not to lipopolysaccharide exposure. Hypoxia-inducible factor-1α is present at high concentrations in the normal equine lamina, and is increased in Obel grade 1 (OG1) stage laminitis in the CHO model of laminitis. Equine lamellar mRNA concentrations of cyclo-oxygenase-2 and inducible nitric oxide synthase, but not glucose transporter 1, are increased in the BWE and CHO models of laminitis.
Conclusions and potential relevance
These data indicate that the normal equine lamellae are profoundly hypoxic in comparison with other tissues. The increased mRNA concentrations of cyclo-oxygenase-2 and inducible nitric oxide synthase 2 in equine keratinocytes exposed to hypoxia and lipopolysaccharide, and in lamellar tissue from BWE and CHO models of sepsis-related laminitis, suggest that the marked lamellar inflammatory gene expression in sepsis-related laminitis may be due to an interaction of constitutively high lamellar keratinocyte HIF-1A signalling with inflammatory signalling, possibly induced by circulating inflammatory mediators.
The Summary is available in Chinese – see Supporting information.