Identification of Two Secreted Phospholipases A2 in Human Epidermis

Abstract

Phospholipases A2 are enzymes that catalyze the release of fatty acids from the sn-2 position of phospholipids. Fatty acids have been suggested to play a key role in the barrier function of the epidermis. The aim of this study was to identify and characterize the type of secretory phospholipase A2 expressed in human epidermis. We report the molecular cloning of two secretory phospholipase A2 in the human epidermis. The first enzyme is identical to human pancreatic type IB phospholipase A2. Western blots revealed a 14 kDa protein localized in the soluble fraction. The second phospholipase A2 is identical to human synovial type IIA enzyme and is localized in the membrane fraction. By semiquantitative reverse transcription-polymerase chain reaction performed on horizontal sections of the epidermis, we found that the mRNAs of both phospholipases A2 were expressed mainly in the basal layers of the epidermis. Our data thus provide evidence for the expression of two secretory phospholipases A2 in human epidermis. The different localization of these two secretory proteins strongly suggests that each enzyme might have a specific role in skin physiology and probably in the barrier function. Taken together, these data validate the reverse transcription-polymerase chain reaction technique performed on thin sections as a first approach to detect gene expression in different layers of the epidermis.

Variability of Enzyme Markers during Clinical Regression of Atopic Dermatitis

“…Type II enzyme, similar to synovial PLA2, is known to occur at low levels throughout the entire epidermis [10]. Our findings indicate that this total PLA2 activity is also significant at the skin surface since rises and falls depend on the extent of inflammation of the stripped area.…”

“…Concerning phospholipase A2-like activity (table 2), it has been shown as resulting from the presence of both type I PLA2 [9] and type II PLA2 [10].…”

“…The improvement of the clinical criteria following the treatment can therefore be related to the drop in PLA2-like activity, most probably that of type II PLA2 [10].…”

“…trypsin-like activity [5], which is involved in desquamation, acid-phosphataselike activity, which is a marker for the degree of regeneration of the barrier function and, finally, the activity of the phospholipase-A2-like enzymes, in particular that involved in the release of arachidonate, a precursor of inflammation mediators [6]. Recent studies have indicated the presence of two secretory PLA2 activities in the upper layers of the epidermis: one similar to pancreatic PLA2 (type I) [7][8][9] and the other resembling synovial PLA2 (type II) [10].…”

Groups IV, V, and X Phospholipases A2s in Human Neutrophils

“…Thus, GIIA and GV sPLA 2 were identified in mouse bone marrow mast cells (23), cultured rat astrocytes (78), and rat neonatal cardiomyocytes, 3 whereas GIB and GIIA sPLA 2 were both identified in epidermis (79) and rat splenic macrophages (80,81). In mast cells, GIIA sPLA 2 was recognized in secretory granules (82), consistent with the putative role of sPLA 2 in facilitating secretory granule exocytosis (83), whereas GV sPLA 2 was identified in the Golgi apparatus, nuclear envelope, and plasma membrane (23).…”