In vivo priming and ex vivo activation of equine neutrophils in black walnut extract-induced equine laminitis is not attenuated by systemic lidocaine administration.

The research aims to investigate the effectiveness of lidocaine, a medication often used for pain management in horses suffering from laminitis, in addressing the activation of neutrophils and related inflammation. Results showed that while lidocaine can aid in pain management, it does not significantly impact the inflammatory response associated with laminitis, even when used at therapeutic levels.

Understanding Laminitis and the Role of Lidocaine

• Laminitis is a severe disease in horses resulting in an inflammatory response within the hoof tissue. It typically causes significant pain, and its management forms a critical part of treatment protocols for the condition.
• Lidocaine is commonly administered systemically to manage this pain, but its potential anti-inflammatory effects have not been thoroughly examined.

Methodology and Experimental Design

• The research focused on whether therapeutic concentrations of lidocaine in horses’ plasma could mitigate neutrophil activation and the associated inflammation.
• Markers of neutrophil activation were identified by stimulating purified neutrophils in vitro with a potent immune-response elicitor, LPS, or with an equine immune-response protein, IL-8. The expression of CD13 and CD18 on the surface of these cells was then measured.
• In vivo analyses were conducted where horses were administered black walnut extract to induce laminitis and, subsequently, systemic lidocaine or a saline control.
• Leukocytes were stained for CD13 and CD18, and protein from laminar tissue was analyzed to measure the accumulation of a neutrophil enzyme, MMP-9.

Key Findings

• Changes in neutrophil size, complexity, CD13 surface expression and CD18 staining intensityoccurred over time post black walnut extract administration irrespective of lidocaine treatment.
• The intensities of neutrophils stained for either CD13 or CD18 did not differ between the samples treated with lidocaine and saline controls, nor did lamellar MMP-9 content.
• These results indicate that while lidocaine can help in managing pain, it does not significantly affect the inflammation caused by the activation of neutrophils.

Therefore, the research provided valuable insights into the use of lidocaine for treating laminitis in horses. While it remains a valuable tool for pain management, its effectiveness against the inflammation that characterizes the disease is not substantial. These findings highlight the need for additional strategies to control the inflammatory responses in laminitics.