Inflammatory effects of platelet activating factor (PAF) in equine skin.

This study investigates how Platelet Activating Factor (PAF), a signaling molecule in the body, influences inflammation and blood flow in horse skin. The research shows that PAF can increase blood vessel permeability and cause white blood cells to infiltrate the skin, while also being influenced by the presence of other substances like histamine and Prostaglandin E2.

PAF’s Inflammatory Effects

• In the research, it was found that injecting PAF into the skin of horses increased the permeability of their blood vessels. This means that it became easier for fluids and cells to pass in and out of the blood vessels.
• Contrastingly, lyso-PAF (a variant form of PAF) did not have this effect. The maximum increase in permeability was observed 32 minutes after injection of PAF.
• The researchers also found that PAF caused an influx of neutrophils, a type of white blood cell, into the skin. This peak was observed two hours after PAF injection, implying an immune response was triggered.

Interactions with other Substances

• When the histamine 1 receptor antagonist chlorpheniramine was coadministered with PAF, the responses to both histamine and PAF were reduced. However, the only statistically significant reduction was observed with histamine-induced responses.
• The administration of indomethacin, a cyclo-oxygenase inhibitor, did not affect the increase in blood vessel permeability caused by PAF. This suggests that the actions of PAF aren’t linked to prostanoid formation, another group of signaling molecules.
• Interestingly, when Prostaglandin E2 (PGE2) was coadministered, the edematous responses (swelling) to both PAF and histamine increased. However, PGE2 itself didn’t directly increase blood vessel permeability.
• In contrast to PAF and histamine, PGE2 was found to increase skin surface temperature and cutaneous blood flow.

Implications and Conclusions

• The researchers believe that their findings suggest PAF may play a role as a mediator in inflammatory skin disorders in horses. It may be involved in increasing blood vessel permeability and triggering immune response, particularly involving neutrophils.
• The interactions between PAF, histamine and PGE2 could also potentially imply the existence of complex regulatory mechanisms in inflammatory responses that could be exploited for therapeutic interventions.