The eosinophil as a cellular source of transforming growth factor alpha in healing cutaneous wounds

Epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha) are known to promote the healing of epithelial wounds. Eosinophils are present in healing wounds and have recently been shown to be capable of producing TGF-alpha. This investigation was done to determine if eosinophils infiltrated into healing wounds are capable of expressing this cytokine. Using the rabbit cutaneous open wound model, the study found that the eosinophil is one of the predominant cell types in the healing wound, beginning from the seventh day and thereafter. Most surprisingly, the majority of the eosinophils present in the healing wound were found to contain TGF-alpha mRNA and protein by in situ hybridization and immunohistochemistry. Thus it is proposed that the delivery of TGF-alpha by eosinophils to epithelial wound healing sites represents a normal body mechanism whereby this multifunctional cytokine can accelerate the wound healing process.

Molecular cloning of the complementary DNA encoding for the hamster TGF-alpha mature peptide

The expression of transforming growth factor alpha (TGF-alpha) is consistently associated with the malignant transformation of oral mucosal tissues in both hamster and human. The cheek pouch of the Syrian hamster represents an ideal model to elucidate the role of TGF-alpha in epithelial cancer development. A prerequisite for such investigations at the molecular level is to obtain hamster-specific TGF-alpha molecular probes. Here we report the successful cloning of the hamster TGF-alpha cDNA from a hamster oral cancer cell line (HCPC-1) by the polymerase chain reaction technique using synthetic oligonucleotide primers based on human TGF-alpha cDNA sequence. Analysis of the nucleotide sequence of the newly isolated hamster cDNA encoding the portion of the mature TGF-alpha peptide revealed that it is 92.6% (139/150) homologous to that of the rat and 93.3% (140/150) homologous to that of the human sequences. The predicted hamster TGF-alpha amino acid sequence is 96% (48/50) similar to that of human, while 94% (47/50) similar to that of rat. Using this hamster TGF-alpha cDNA as a probe, molecular hybridization experiments revealed that it detects hamster TGF-alpha mRNA with approximately 40 times and approximately 5 times greater sensitivity than similar probes from human and rat origin respectively. This hamster TGF-alpha cDNA should be of great value as a probe to evaluate the role of TGF-alpha in the normal and pathological processes using the hamster as an experimental model.

Production of transforming growth factor alpha by hamster eosinophils

Previously it was demonstrated that malignant transformation of the Syrian hamster cheek pouch mucosa is associated with the expression of TGF-alpha. Therefore in situ hybridization and immunohistochemistry was used to investigate the cellular sources of TGF-alpha production in this model system. Surprisingly one cell type in the inflammatory infiltrate present in the connective tissue adjacent to the transformed epithelium represented a major source of TGF-alpha mRNA. Detailed analysis of these cells revealed that they were eosinophils. In addition to TGF-alpha mRNA, about 40% of the eosinophils associated with the oral tumors exhibited TGF-alpha product reactive with a monoclonal antibody against the C terminus of the mature TGF-alpha peptide. Normal hamster bone marrow eosinophils also exhibited TGF-alpha mRNA and product by in situ hybridization and immunohistochemistry. These results suggest that the eosinophil represents a biologically significant source of TGF-alpha.

Yields of fibronectin by heparin-cold-precipitation from plasma

Fibronectin prepared by heparin-cold-precipitation from 10 packs each of 24-hour plasma, stored plasma and 6-hour frozen plasma was assayed by electroimmunodiffusion. Its yield obtained from 24-hour plasma was significantly higher than that from stored plasma (p less than 0.01) indicating a decline with storage. Freezing of plasma within 6 hours retards degradation of fibronectin. Therefore, 24-hour plasma or 6-hour frozen plasma should be used to prepare fibronectin in order to achieve a better yield.

Human eosinophils express transforming growth factor alpha

Transforming growth factor alpha (TGF-alpha) is a pleuripotential cytokine with diverse biological effects, including the ability to influence the proliferation of normal cells or neoplastic epithelial cells. Eosinophils are a subset of granulocytes that normally enter the peripheral tissues, particularly those beneath gastrointestinal, respiratory, and urogenital epithelium, where they reside in close proximity to the epithelial elements. In this study, we demonstrate that the great majority of eosinophils infiltrating the interstitial tissues adjacent to two colonic adenocarcinomas and two oral squamous cell carcinomas labeled specifically by in situ hybridization with a 35S-riboprobe for human TGF-alpha (hTGF-alpha). No other identifiable leukocytes in these lesions contained detectable hTGF-alpha mRNA. We also examined leukocytes purified from a patient with the idiopathic hypereosinophilic syndrome. 80% of these eosinophils, but none of the patient's neutrophils or mononuclear cells, were positive for hTGF-alpha mRNA by in situ hybridization, and 55% of these eosinophils were positive by immunohistochemistry with a monoclonal antibody directed against the COOH terminus of the mature hTGF-alpha peptide. Finally, the identification of the purified eosinophil-associated transcript as hTGF-alpha was confirmed by polymerase chain reaction product restriction enzyme analysis followed by Southern blot hybridization. In contrast to eosinophils from the patient with hypereosinophilic syndrome, the peripheral blood eosinophils from only two of seven normal donors had detectable TGF-alpha mRNA and none of these eosinophils contained immunohistochemically detectable TGF-alpha product. Taken together, these findings establish that human eosinophils can express TGF-alpha, but suggest that the expression of TGF-alpha by eosinophils may be under microenvironmental regulation. Demonstration of TGF-alpha production by tissue-infiltrating eosinophils and the eosinophils in the hypereosinophilic syndrome identifies a novel mechanism by which eosinophils might contribute to physiological, immunological, and pathological responses.

Binding of platelet activating factor by isolated membranes from U937 cells

Platelet activating factor (PAF), 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (1-O-alkyl-2-acetyl-GPC) has been known to have biological effect on cells. The mechanisms of the effect of the potent phospholipid on cells has not been established. We have used 1-O-[3H]alkyl-2-acetyl-GPC [( 3H]PAF) to study the interaction on the isolated membranes of U937 cells. The binding process was time, protein concentration, temperature dependent and reversible. The binding of [3H]PAF to the U937 cell membranes was slightly inhibited by the addition of PAF analogue, 3-O-Hexadecyl-2-acetyl-sn-glycerol-1-phosphorylcholine. U937 cell membranes showed high affinity binding sites for PAF with equilibrium dissociation constant (Kd) of 5 x 10(-9) M. The displacement of bound [3H]PAF with 500-fold excess of nonlabeled PAF was not altered suggesting that the bound [3H]PAF was not degraded during the binding. Binding of [3H]PAF on U937 cell membranes was inhibited by PAF antagonist, 59227RP. The kinetic of the inhibition by PAF antagonist is competitive suggesting that PAF and PAF antagonist bind at the same site.