Suppression of RNA synthesis in lymphocytes by inhibitors of proteolytic enzymes

Interaction between alpha 1 antitrypsin and lymphocyte surface proteases: immunoregulatory effects

Alpha 1 antitrypsin (alpha 1-AT) is the major plasma protease inhibitor. Radioiodinated alpha 1-AT binds to human lymphocytes. The binding is fast and reversible, and the cells can be saturated with a maximum of approximately 1.2 x 10(6) molecules of alpha 1-AT per lymphocyte. The receptor for alpha 1-AT is a surface-associated protease. Addition of alpha 1-AT completely inhibits cell surface proteolytic activity. Furthermore alpha 1-AT decreases 3H-thymidine incorporation into lymphocytes stimulated by B or T cell mitogens or by allogeneic cells. Since alpha 1-AT was shown to be produced by activated monocytes and to bind to lymphocytes, it is likely to represent a mediator of monocyte-lymphocyte interactions.

Modification of lymphocyte DNA synthesis by alpha 1-antitrypsin

Purified human alpha 1-antitrypsin (alpha 1-AT) was shown to inhibit 3H-thymidine incorporation into mouse or human lymphocytes stimulated by various mitogens or by allogeneic cells. In the mouse, both B- and T-cell responses were affected. In the human, proliferative responses of peripheral blood lymphocytes, thymocytes and T-enriched tonsillar lymphocytes to phytohaemagglutinin were inhibited as well as that of tonsillar lymphocytes to Salmonella typhi-murium lipopolysaccharide. Spontaneous 3H-thymidine incorporation was moderately and inconstantly decreased, without evidence of altered cell viability. The inhibitory effect of alpha 1-AT appears to be related to its protease inhibitory capacity. These data bring further evidence for the role of proteolytic enzymes in the early events of lymphocyte activation, and support the hypothesis that serum inhibitors of proteases may contribute to the modulation of the immune response.

Evidence for translational control of the binding of 7, 12-dimethylbenz[a]anthracene to DNA of murine epidermal cell in culture

The effects of various inhibitors of aryl hydrocarbon hydroxylase (AHH), antioxidants, inhibitors of DNA, RNA, and protein synthesis, and protease inhibitors on the binding of [7,12-3H]dimethylbenz[a]anthracene ([3H] DMBA) to DNA of murine epidermal cells in culture have been investigated. 7,8-Benzoflavone, 5,6-benzoflavone and methyrapone (inhibitors of AAH) and antioxidants, butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT), efficiently reduced the binding of [3H] DMBA to cellular DNA. Inhibitors of DNA and RNA synthesis did not affect this process whereas inhibitors of protein synthesis suppressed the binding of [3H] DMBA to cellular DNA. Protease inhibitors p-tosylamide-2-phenylchloromethyl ketone (TPCK) and p-tosyl-L-lysine chloromethyl ketone (TLCK) also reduced the interaction between DMBA and DNA. Thus, it appears that binding of DMBA to cellular DNA is regulated at the level of translation or/and post translation.

[The effect of proteinase inhibitor aprotinin on RNA-synthesis rate after partial hepatectomy in rats (author's transl)]

The effect of Aprotinin has been investigated on RNA-synthesis rate--measured by the incorporation of 3H-uridine--after partial hepatectomy in rats. In the control group two maxima of the incorporation of 3H-uridine into the regenerating liver were obtained after hepatectomy. On the other hand no increase of the 3H-uridine incorporation was detectable after Aprotinin pretreatment. The results indicate that Aprotinin inhibits the early events of liver regeneration by inhibition of proteinase enzymes.

Changes in the fine structure of the human dental pulp subsequent to carious exposure

Sections of human pulp tissue taken from the region of a carious exposure in four young patients each having a clinical history of spontaneous dental pain were examined with the electron microscope. All the tissues examined exhibited a generalized edema, and an infiltration with lymphocytes, plasma cells, polymorphonuclear leukocytes and macrophages. Varying degree of lysis of pulp and inflammatory cells were evident. The unmyelinated nerve axons of the pulp appeared to be least affected. Extracellular lysosomes were present in many of the necrotic areas. Edematous vacuoles were noted in two of the pulp specimens. In some of the sections these vacuoles appeared to be responsible for a physical distortion of adjacent unmyelinated nerve axons. It was postulated that such distortion may be a contributing factor to the pain of pulpitis. In another of the pulp specimens, micro-organisms were found intracellularly and extracellularly. Intracellularly they were present within the cytoplasm of polymorphonuclear leukocytes and macrophages and exhibited evidence of lysis. Only two morphological forms, a gram positive rod, and a gram positive coccus were identified.

Lymphocyte stimulation: a rapid multiparameter analysis

Several parameters of stimulation of individual lymphocytes are measured simultaneously by flow-cytofluorometry after differential staining of cellular DNA and RNA with the metachromatic fluorescent dye acridine orange. The method provides a means of analyzing the progression of stimulated cells through the cell cycle (G1, S and G2 + M), in addition to measuring the accumulation of RNA per cell; the RNA parameter is useful in distinguishing G1 from G0 cells. The multiparameter analysis may be of unique value in discriminating cases where the transcriptional and proliferative responses of lymphocytes to stimulants are not correlated.

Investigations of the possible role of proteases in altering surface proteins of virally transformed hamster fibroblasts

Virally transformed fibroblasts have on their surfaces zero or reduced amounts of a large external transformation-sensitive (LETS) glycoprotein. This protein is extremely sensitive to proteolysis. When prelabeled normal fibroblasts are cocultivated with transformed cells, the LETS glycoprotein of the normal cells shows an increased rate of turnover. Experiments are described which investigate the possibility that this phenomenon and the absence of LETS glycoprotein are due to proteolysis by the transformed cells. In particular, the role of plasminogen activation is examined by the use of protease inhibitors and plasminogen-depleted serum. It is concluded that activation of plasminogen is not required for the disappearance of the LETS glycoprotein although the involvement of other proteases cannot be ruled out. The role of proteases in affecting cell growth and behavior is discussed.

Intracellular distribution of neutral proteinases and inhibitors in pig leucocytes. Isolation of two inhibitors of neutral proteinases

Granule and post-granular-supernatant fractions were obtained from pig leucocyte cells by differential centrifugation in 0.34 M sucrose. Granule extract possesses proteinase activity at acid and at neutral pH. Three groups of neutral and a group of acid proteinases were isolated from granule extracts by chromatography on DEAE-cellulose. In the first group are present elastase-like and plasminogen-activator proteinases, that are inhibited by diisopropylphosphorofluoridate, alpha1-antitrypsin, intracellular leucocyte inhibitor and partly with p-aminomethylbenzoic acid and Trasylol. The second group of neutral proteinases is unstable under the conditions of isolation used the third group of neutral proteinases comprises collagenases that are inhibited by ethylenediamine tetraacetic acid disodium salt, alpha1-antitrypsin and leucocyte inhibitor. The acid proteinases are inhibited only with pepstatin, up to 90%. In the post-granular supernatant was found the acid proteinase activity towards hemoglobin and casein, and non-stable neutral proteolytic activity towards bovine serum albumin and serum gamma globulin. In the post-granular supernatant also the inhibitors of neutral proteinases were found. By gel filtration on Sephadex G-100 and ion-exchange chromatography on CM-cellulose two inhibitors of neutral proteinases were isolated. The majority of the inhibitor capacity (about 80%) of post-granular supernatant was eluted together with ovalbumin (Mr 43000) and the remainder with cytochrome c (12300). These inhibitors inhibit the granule neutral proteinases, acting on all substrates used, but do not inhibit granule acid proteinase. Inhibition effects of post-granular-supernatant inhibitors on trypsin and chymotrypsin were obtained only when bovine serum albumin was used as substrate. Inhibitors of post-granular supernatant are stable at pH 6-8, but unstable in the pH rnage 2-5 and are thermolabile.