Response of the Endothelium to the Epicutaneous Application of Leukotriene B4

Atopic Patients Show Increased Interleukin 4 Plasma Levels but the Degree of Elevation Is Not Sufficient to Upregulate Interleukin-4-Sensitive Genes

BACKGROUND

Atopic diseases constitute a major health challenge for industrialized countries, and elevated levels of interleukin 4 (IL-4) frequently characterize these disorders. Previous in vitroanalyses have indicated that IL-4 strongly upregulates the expression of IL-4-sensitive genes in human monocytes.

OBJECTIVE

To explore whether similar expression alterations may contribute to the pathomechanisms of atopic diseases in vivo we carried out a small-scale case-control clinical study (n = 43), in which we quantified the plasma levels of IgE and IL-4 as well as the expression of selected IL-4-sensitive genes in blood leukocytes.

METHODS

34 allergic patients suffering from allergic rhinitis (n = 11), atopic eczema (n = 11) and allergic asthma (n = 12) as well as 9 healthy control individuals were recruited. IgE and IL-4 plasma levels were determined by ELISA, and the expression of selected IL-4-sensitive gene products in blood leukocytes was quantified by qRT-PCR. In addition, the fatty acid oxygenase activity of isolated monocytes was measured by RP-HPLC analysis of the arachidonic acid oxygenation products (ex vivo activity assays).

RESULTS

We found that plasma levels of IgE and IL-4 were significantly elevated in atopic patients but the degree of elevation was not sufficient to upregulate the expression of the selected IL-4-sensitive genes in circulating leukocytes. Moreover, the arachidonic acid oxygenase activity of blood monocytes was not significantly altered in atopic patients.

CONCLUSION

Our data suggest that the IL-4 plasma levels of atopic patients are not high enough to impact the expression of IL-4-sensitive genes.

The dynamics of endothelial changes in vivo following standardized skin injury

BACKGROUND

Vascular changes, that is, functional and cellular endothelial changes, are of essential importance in healing. Alongside these vascular changes, inflammatory factors and hypoxia may play an important role in recovery.

OBJECTIVES

To investigate the dynamics of functional and cellular endothelial changes and hypoxia in vivo following standardized skin damage caused by tape stripping.

METHODS

Vascular changes (endothelial cell proliferation, vascular network size, vessel diameter) and hypoxia-inducible factor-1α were examined immunohistochemically using a CD31/Ki67 double staining and HIF-1α single staining. Cutaneous perfusion was evaluated using the Twente Optical Perfusion Camera (TOPCam).

RESULTS

The initial phase is seen to be dominated by endothelial cell proliferation, HIF-1α expression, and vasodilatation. Cutaneous perfusion intensity is particularly increased in the first 16 hours. The late phase of recovery (after 72 hours) is characterized by a peak of expansion of the vascular network and a second peak of endothelial cell proliferation and HIF-1α expression.

CONCLUSION

Endothelial cell proliferation and HIF-1α expression appear to be (strongly) related, having maximum levels at 16 hours and 72 hours. Angiogenesis and HIF-1α expression are not continuous processes, but rather occur intermittently.