Indices of inflammation in the lung and liver in the early stages of the black walnut extract model of equine laminitis.

This study investigates the role of the liver and lungs, as sources of inflammatory mediators, in the black walnut extract model of equine laminitis—an inflammation of the horse’s hoof. The researchers used real-time quantitative PCR to measure different pro-inflammatory and anti-inflammatory cytokines in the liver and lungs at various time points, while also assessing leukocyte immigration into these organs. The findings indicate that there are significant changes in cytokine expression and leukocyte numbers in the liver and lungs early on in development of laminitis.

Research Methods

The research was conducted through the following methods:

• Black walnut extract (BWE) model of equine laminitis was used for the study. This is an established veterinary model which mimics the inflammation in horses’ hooves observed in laminitis.
• Hepatic (liver) and pulmonary (lung) samples from horses were analysed at two time points in the early developmental period of the disease—1.5 hours post-BWE administration and at the “developmental time point” (approximately 3 hours post-BWE administration), when the onset of leukopenia (decrease in the number of white blood cells) is typically observed.
• Real-time quantitative PCR (RT-qPCR) was used to measure mRNA concentrations of various cytokines in these samples. These cytokines included both proinflammatory (those that aggravate inflammation, such as IL-6, IL-8 and TNF-alpha), and anti-inflammatory (those that reduce inflammation, such as IL-10 and IL-4) types.
• CD13 immunohistochemistry, a lab technique, was used to assess the movement of leukocytes (white blood cells that fight infection) into the liver and lungs.

Research Findings

The findings of the study were as follows:

• The mRNA concentrations of the proinflammatory cytokines IL-6, IL-8 and TNF-alpha significantly increased in liver and lung samples in the early stages of laminitis. However, these increases were significantly smaller than those previously reported for laminae (the sensitive tissue within the horse’s hoof).
• IL-1beta, another proinflammatory cytokine, showed increased concentration only in the lungs.
• The anti-inflammatory cytokines, IL-10 and IL-4, showed transient decreases at different time points during the disease development.
• Significant increases in the numbers of leukocytes were observed in both the liver and lungs. This suggests that these organs are active sites of inflammation and could be potential sources of inflammatory mediators.

Implication of the Findings

• The findings suggest that the liver and lungs, due to their increased cytokine production and leukocyte movement, may play a role in the systemic inflammation observed in equine laminitis.
• They also reveal that the expression of proinflammatory cytokines in these organs differs from that in the laminae, and also peaks later in the disease process—providing valuable insights into the temporal and spatial progression of this disorder.
• Understanding these mechanisms could potentially lead to the development of more targeted therapies for equine laminitis.