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Home / Equine Research Bank / Vet Res / Expression of toll-like receptor 4 and 2 in horse lungs.
Veterinary research2006; 37(4); 541-551; doi: 10.1051/vetres:2006017

Expression of toll-like receptor 4 and 2 in horse lungs.

Abstract: Toll-like receptor (TLR) is a key component in launching innate immune response to microbial challenge. TLR4 and TLR2 are recognized as specific receptors for components of Gram-negative and Gram-positive bacteria, respectively. Horses are extremely sensitive to endotoxin-induced cardiopulmonary distress and mortality which causes significant economic losses. To date, there are no data on the expression of TLR4 and TLR2 in horse lungs. Therefore, we examined the expression of TLR4 and TLR2 in lungs from normal or Escherichia coli lipopolysaccharide (E. coli LPS; 50 ng/kg; iv) treated horses. We also studied the impact of the depletion of pulmonary intravascular macrophages (PIM) on TLR4 and TLR2 expression in normal or LPS-treated horses. RT-PCR showed TLR4 mRNA but not TLR2, in normal horse lungs. PIM depletion reduced TLR4 mRNA expression without affecting TLR2. The LPS treatment increased the expression of TLR4 and TLR2 mRNA in normal and PIM-depleted horses compared to normal saline-treated horses. Light and electron microscopic immunocytochemistry showed TLR4 protein in PIM, alveolar macrophages and septal endothelium in lungs from normal or LPS-treated horses. Immuno-gold electron microscopy showed TLR4 in PIM and dual-label immuno-electron microscopy co-localized TLR4 and LPS in the cytoplasm and nucleus of PIM of LPS-treated horses. The present manuscript is the first report on the expression of TLR4 and TLR2 in normal and LPS-treated horses and direct co-localization of TLR4 with LPS molecules in PIM. These data provide evidence that PIM are equipped with TLR4 to handle and rapidly respond to circulating endotoxins.
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Publication Date: 2006-04-28 PubMed ID: 16641015DOI: 10.1051/vetres:2006017Google Scholar: Lookup
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  • Journal Article
  • Research Support
  • Non-U.S. Gov't

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research investigates the expression of specific receptors (TLR4 and TLR2) in horse lungs, which are critical in responding to bacterial infections. It is the first of its kind to provide evidence on this topic, revealing how these receptors react to endotoxins and their role in the immune response.

Introduction

  • This study investigates the toll-like receptors (TLR) 2 and 4 in the lungs of horses. These receptors are essential parts of the immune response system, particularly in identifying and responding to bacterial infections. TLR4 specifically recognizes components of Gram-negative bacteria, while TLR2 is associated with Gram-positive bacteria.
  • It is well-established that horses are highly sensitive to endotoxin-induced cardiopulmonary distress, which leads to significant economic impact due to increased mortality rates. However, scant data exist on the expression of TLR2 and TLR4 in horse lungs, which this study seeks to address.

Methodology

  • Researchers examined the expression of TLR4 and TLR2 in horse lungs under normal conditions or following treatment with E. coli lipopolysaccharide (LPS), a component of Gram-negative bacterial cell walls. They also studied the effects of depleting pulmonary intravascular macrophages (PIMs), which are important cells in the immune response.

Results

  • The study discovered that TLR4 mRNA (biological precursors to the actual protein receptors) is expressed in normal horse lungs, but not TLR2.
  • Upon the depletion of PIM, TLR4 mRNA expression was reduced without any effect on TLR2 expression.
  • Following LPS treatment, both TLR2 and TLR4 mRNA expression levels increased, in both normal horses and those with depleted PIMs.
  • Imaging techniques found TLR4 protein in PIMs, alveolar macrophages and septal endothelium in the lungs, from both normal and LPS-treated horses. Further detailed imaging revealed that TLR4 and LPS were co-localized in the cytoplasm and nucleus of PIMs in LPS-treated horses.

Conclusion

  • The data from this research is the first to report the expression of TLR2 and TLR4 receptors in normal and LPS-treated horses. It suggests that PIMs in horse lungs are equipped with TLR4 receptors and can swiftly respond to circulating endotoxins, providing a critical element in the immune response.

Cite This Article

APA
Singh Suri S, Janardhan KS, Parbhakar O, Caldwell S, Appleyard G, Singh B. (2006). Expression of toll-like receptor 4 and 2 in horse lungs. Vet Res, 37(4), 541-551. https://doi.org/10.1051/vetres:2006017

Publication

Veterinary research
ISSN: 0928-4249
NlmUniqueID: 9309551
Country: England
Language: English
Volume: 37
Issue: 4
Pages: 541-551

Researcher Affiliations

Singh Suri, Sarabjeet
  • Immunology Research Group, Departments of Veterinary Biomedical Sciences, University of Saskatchewan, 52 Campus Drive, Saskatoon, SK S7N5B4, Canada.
Janardhan, Kyathanahalli S
    Parbhakar, Om
      Caldwell, Sarah
        Appleyard, Greg
          Singh, Baljit

            MeSH Terms

            • Animals
            • Gene Expression Regulation
            • Horses / metabolism
            • Immunohistochemistry
            • Lung / cytology
            • Lung / metabolism
            • Macrophages / metabolism
            • Male
            • RNA, Messenger / metabolism
            • Toll-Like Receptor 2 / metabolism
            • Toll-Like Receptor 4 / metabolism

            Citations

            This article has been cited 13 times.
            1. Balachandran Y, Caldwell S, Aulakh GK, Singh B. Regulation of TLR10 Expression and Its Role in Chemotaxis of Human Neutrophils. J Innate Immun 2022;14(6):629-642.
              doi: 10.1159/000524461pubmed: 35613551google scholar: lookup
            2. Bocking T, Singh B. Light and electron-microscopic localization of CD9 and surfactant protein A and D in normal lungs of the horse. Can J Vet Res 2021 Jul;85(3):170-176.
              pubmed: 34248260
            3. Le NPK, Gerdts V, Singh B. Integrin alpha-v/beta3 expression in equine lungs and jejunum. Can J Vet Res 2020 Oct;84(4):245-251.
              pubmed: 33012972
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              doi: 10.3892/mmr.2017.6129pubmed: 28098883google scholar: lookup
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              doi: 10.1186/s12864-016-3390-ypubmed: 28056766google scholar: lookup
            6. Karagianni AE, Kapetanovic R, McGorum BC, Hume DA, Pirie SR. The equine alveolar macrophage: functional and phenotypic comparisons with peritoneal macrophages. Vet Immunol Immunopathol 2013 Oct 1;155(4):219-28.
              doi: 10.1016/j.vetimm.2013.07.003pubmed: 23978307google scholar: lookup
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              doi: 10.1111/j.2042-3306.2012.00574.xpubmed: 22607193google scholar: lookup
            8. Lewis DH, Chan DL, Pinheiro D, Armitage-Chan E, Garden OA. The immunopathology of sepsis: pathogen recognition, systemic inflammation, the compensatory anti-inflammatory response, and regulatory T cells. J Vet Intern Med 2012 May-Jun;26(3):457-82.
              doi: 10.1111/j.1939-1676.2012.00905.xpubmed: 22428780google scholar: lookup
            9. Schneberger D, Lewis D, Caldwell S, Singh B. Expression of toll-like receptor 9 in lungs of pigs, dogs and cattle. Int J Exp Pathol 2011 Feb;92(1):1-7.
              doi: 10.1111/j.1365-2613.2010.00742.xpubmed: 21044185google scholar: lookup
            10. Aharonson-Raz K, Singh B. Pulmonary intravascular macrophages and endotoxin-induced pulmonary pathophysiology in horses. Can J Vet Res 2010 Jan;74(1):45-9.
              pubmed: 20357958
            11. Gill SS, Suri SS, Janardhan KS, Caldwell S, Duke T, Singh B. Role of pulmonary intravascular macrophages in endotoxin-induced lung inflammation and mortality in a rat model. Respir Res 2008 Oct 24;9(1):69.
              doi: 10.1186/1465-9921-9-69pubmed: 18950499google scholar: lookup
            12. Tang X, Metzger D, Leeman S, Amar S. LPS-induced TNF-alpha factor (LITAF)-deficient mice express reduced LPS-induced cytokine: Evidence for LITAF-dependent LPS signaling pathways. Proc Natl Acad Sci U S A 2006 Sep 12;103(37):13777-82.
              doi: 10.1073/pnas.0605988103pubmed: 16954198google scholar: lookup
            13. Rodrigues CR, Aulakh GK, Kroeker A, Kulkarni SS, Lew J, Falzarano D, Singh B. Recruitment of pulmonary intravascular macrophages in SARS-CoV-2 infected hamsters. Cell Tissue Res 2025 Apr;400(1):1-15.
              doi: 10.1007/s00441-025-03958-2pubmed: 40014090google scholar: lookup
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