Natural Protein Toxins Affecting Cutaneous Microvascular Permeability

Abstract

Natural toxins are found widespread from animal, plant and micro-organism sources. Presented here in review are recently discovered natural protein toxins that have in some way been shown to affect the permeability of the cutaneous micro-vasculature or skin capillaries.

Capillaries play a major role in the body by controlling the necessary normal balance of metabolites in the body's tissues and that of the blood. The trans-capillary exchanges of water and metabolites are regulated by the basal lamina, the internal activities of the endothelial cells and the driving forces on each side of the capillary wall. Edema, inflammation, urticaria, increased capillary permeability and cutaneous edema are conditions that are related. The main methods for detecting the increase in skin capillary permeability have been by using the rat paw edema assay, labelled albumin, or other detectable indicators.

Natural venoms and toxins sources causing edema include mammals, reptiles, amphibians, fishes, invertebrates, plants, and micro-organisms. Not all the substances causing increased capillary permeability are proteins such as certain alkaloids (Plants, fungi, fire ants and others) and normal endogenous substances e.g. histamine, serotonin, acetylcholine, (plants, snakes, and others) and are not considered in this review.

Recently, a large number of toxins (predominantly bacterial toxins) have been reported that produce increased cutaneous capillary permeability, some of which are known in some detail and selected toxins are discussed.

These studies have helped to understand the toxins, provided for more effective treatments, and helped to improve our knowledge of the capillaries and endothelial cells.