Molecular weight alterations of alpha-1 proteinase inhibitor in equine bronchoalveolar lavage fluid.

The research article discusses the variation in molecular weight of alpha-1 proteinase inhibitor (alpha 1PI) in equine bronchoalveolar lavage fluid (BALF). It indicates that the molecular weight of alpha 1PI and albumin in BALF changes significantly compared to that in serum.

Background of the Study

• The initial focus is on the difference between the equine and human alpha 1PI system. It points out that while in humans, there is a single gene encoding for alpha 1PI, in horses there are four interrelated genes (Spi1-Spi4).

Previous Findings

• Researchers have previously observed differences between the proportions of Spi proteins in equine serum and bronchoalveolar lavage fluid (BALF).
• On this basis, their interest is to find out if there is also any molecular weight difference between the Spi proteins in serum and BALF, similar to what has been reported in humans.

Methodology and Results

• To analyze this, they used alpha 1PI and albumin from equine BALF, migration of these proteins was further towards the anode compared to serum alpha 1PI using native polyacrylamide gel electrophoresis (PAGE).
• The significant difference was however only observed for alpha 1PI.
• Using Sodium dodecyl sulphate-PAGE (SDS-PAGE), they identified an average decrease in molecular weight of 1.5 kDa for alpha 1PI and 1.3 kDa for albumin in BALF compared to serum.
• This finding was consistent in both healthy animals as well as animals suffering from symptomatic or asymptomatic chronic obstructive pulmonary disease (COPD).

Possible Causes of Molecular Weight Difference

• The study suggests that unlike reports in humans where bacterial proteinases cleave alpha 1PI, the mechanism behind the decrease in molecular weight in horses is probably different as the change in molecular weight was relatively small and no loss of trypsin inhibitory activity was observed.
• Furthermore, there was no evidence of bacterial infection in their system that could account for the weight change.
• The study proposes that damage due to endogenous proteinases or glycosidases at a site other than the reactive site may cause this decreased molecular weight.

Implications of the Study

• The impact of these variations on the efficiency of the antiproteinase screen in the lower respiratory tract, however, remains uncertain, indicating an area where further research could be beneficial.