Effect of composition and different fractions of hay dust suspension on inflammation in lungs of heaves-affected horses: MMP-9 and MMP-2 as indicators of tissue destruction.

The research analyzes the effects that different elements of organic dust might have on the increase of matrix metalloproteinases (MMPs) levels—associated with tissue destruction—in the airways of horses prone to a respiratory condition called heaves. The study is particularly concerned with the role of molds.

Research Methodology

• To discern the connection between organic dust components and MMP elevation, the researchers ran tests on bronchoalveolar lavage (BALF) samples obtained from seven horses susceptible to heaves.
• The horses were exposed to different inhalation challenge tests: normal saline, two distinct hay dust suspensions (HDS-1 and HDS-2), and soluble and particulate fractions of HDS-1.
• BALF samples, taken six hours post-inhalation challenge, were evaluated to measure MMP-2 and MMP-9 levels, with SDS-page gelatin zymography technique.

Research Findings

• HDS-1 challenge caused an increase in BALF proMMP-9 and total MMP-9 levels.
• The increase in proMMP-9 and total MMP-9 occurred only when the soluble and particulate fractions of HDS-1 were combined or when lipopolysaccharide was added to the particulate fraction, not when inhaled separately.
• HDS-2 inhalation led to elevated levels of complex forms, proMMP-9, active MMP-9, total MMP-9, and total MMP-2 in BALF.

Conclusions

• The results show that soluble and particulate organic dust components work together to bring about the increase in MMPs.
• The varying glucan concentrations in HDS-1 and HDS-2 suggest that molds play a significant part in activating MMP-9 levels.
• The activations and releases of MMPs due to inhaled molds are seen to be involved in the development and cause of heaves.
• While the endotoxin does contribute to the action of the dust components, the overall MMP response to organic dust inhalation is largely reflected by the mold content in the dust.
• The researchers speculate that inhibiting the production and release of MMPs could be an effective strategy in treating and preventing heaves in the future, and provide recommendations for acceptable dust levels.