Increased Protein Tyrosine Kinase Activity of the Colonic Mucosa in Ulcerative Colitis Y . SAKANOUE, T. HATADA, T. HORAI, T. OKAMOTO, M. KUSUNOKI & J. UTSUNOMTYA Second Dept. of Surgery, Hyogo College of Medicine, Hyogo, Japan Sakanoue Y, Hatada T, Horai T , Okamoto T, Kusunoki M, Utsunomiya J . Increased protein tyrosine kinase activity of the colonic mucosa in ulcerative colitis. Scand J Gastroenterol 1992;27:686-690.
Scand J Gastroenterol Downloaded from informahealthcare.com by Queen's University on 12/30/14 For personal use only.
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Thc protein tyrosine kinase (PTK) activity was measured in the inflamed colonic mucosa of 12 paticrits with ulcerative colitis and in the normal colonic mucosa of 12 control patients with colon cancer. The specific PTK activity in the particulate fraction obtained from ulcerative colitis mucosa was significantly increased compared with that of normal mucosa (5.10 t 0.60 pmol/min/mg versus 2.12 k 0.44 pmol/ min/mg protein; p < 0.05). Inflamed ulcerative colitis mucosa also showed a significantly higher total PTK activity in the particulate fraction than normal mucosa (2.60 -+ 0.42 pmol/min/g versus 0.91 2 0.16 pmol/min/g tissue; p < 0.05). Mucosal samples from ulcerative colitis patients werc divided into those with mild and those with severe inflammation on histologic examination (n = 6 each). The particulate PTK activity of severely inflamed mucosa was significantly higher than that of mildly inflamed mucosa (p < 0.05). These results suggest that colonic inflammation in ulcerative colitis is associated with alterations in cellular PTK activity
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Key word,s: Protein tyrosine kinasc; ulcerative colitis Youichirou Sakanoue, M . D.,Second D e p . of Surgery, Hyogo College of Medicine, 1-1 Mukogawu-cho, Nkhinomiya, Hyogo, Japan 663
Protein tyrosine kinase (PTK) is an enzyme that phosphorylates the tyrosine residues of protein substrates. Tyrosine phosphorylation is now recognized as an important regulatory mechanism in several important cellular processes. including the actions of several growth factors and oncogenes (1). This regulatory process involves the activation of membrane-bound PTK, which subsequently leads to the phosphorylation of various target proteins. Levine (2) exposed various culture cells to micromolar concentrations of vanadate (which is known to inhibit protein tyrosine-phosphate phosphatases) and found that deesterification of lipids was positively regulated by tyrosine phosphorylation in some cells, whereas the lipoxygenase activity of leukocytes was negatively regulated, at least in part, by tyrosine phosphorylation. Ulcerative colitis (UC) is an inflammatory disease of unknown etiology. The role of soluble mediators that amplify and modulate the inflammatory response in this disease has generated great interest, with emphasis being placed on the role played by arachidonic acid metabolites (3). Many in vitro studies have demonstrated an increased arachidonic acid content in the colonic mucosa of U C patients and an increase in the prostaglandin and leukotriene contents of U C biopsy specimens and rectal mucosal cultures, respectively (4-6). Many compounds that stimulate arachidonic acid metabolism also affect PTK. It thus seemed worthwhile to us to determine the PTK activity in the inflamed colonic mucosa
of U C patients. In this study we examined the PTK activity in the cytosolic and particulate fractions of colonic mucosal homogenates obtained from U C patients and normal controls. MATERIALS AND METIIODS
Subjects All patients gave informed consent for this study, which was also approved by the Institutional Ethical Committee. The subjects were 12 patients with UC and 12 with colon cancer who underwent surgery at the Second Dept. of Surgery at Hyogo College of Medicine between October 1988 and August 1990. Mucosal samples Inflamed colonic mucosal samples were obtained from the 12 patients with UC, who included 6 women and 6 men with a mean age of 26 years (range, 13-42 years). All patients had extensive disease and were receiving treatment with prednisolone at the time of surgery. The mean duration of disease was 7 years in this group (range, 2-11 years). Histologically normal mucosal samples were obtained from the 12 patients with colon cancer, who included 6 women and 6 men with a mean age of 54 years (range, 4968 years). None of these were receiving any treatment with steroids or other anti-inflammatory drugs, and this group served as controls.
PTK Activity in Ulcerative Colitis
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P
Scand J Gastroenterol Downloaded from informahealthcare.com by Queen's University on 12/30/14 For personal use only.
T-
Thc protein tyrosine kinase (PTK) activity was measured in the inflamed colonic mucosa of 12 paticrits with ulcerative colitis and in the normal colonic mucosa of 12 control patients with colon cancer. The specific PTK activity in the particulate fraction obtained from ulcerative colitis mucosa was significantly increased compared with that of normal mucosa (5.10 t 0.60 pmol/min/mg versus 2.12 k 0.44 pmol/ min/mg protein; p < 0.05). Inflamed ulcerative colitis mucosa also showed a significantly higher total PTK activity in the particulate fraction than normal mucosa (2.60 -+ 0.42 pmol/min/g versus 0.91 2 0.16 pmol/min/g tissue; p < 0.05). Mucosal samples from ulcerative colitis patients werc divided into those with mild and those with severe inflammation on histologic examination (n = 6 each). The particulate PTK activity of severely inflamed mucosa was significantly higher than that of mildly inflamed mucosa (p < 0.05). These results suggest that colonic inflammation in ulcerative colitis is associated with alterations in cellular PTK activity
2
Key word,s: Protein tyrosine kinasc; ulcerative colitis Youichirou Sakanoue, M . D.,Second D e p . of Surgery, Hyogo College of Medicine, 1-1 Mukogawu-cho, Nkhinomiya, Hyogo, Japan 663
Protein tyrosine kinase (PTK) is an enzyme that phosphorylates the tyrosine residues of protein substrates. Tyrosine phosphorylation is now recognized as an important regulatory mechanism in several important cellular processes. including the actions of several growth factors and oncogenes (1). This regulatory process involves the activation of membrane-bound PTK, which subsequently leads to the phosphorylation of various target proteins. Levine (2) exposed various culture cells to micromolar concentrations of vanadate (which is known to inhibit protein tyrosine-phosphate phosphatases) and found that deesterification of lipids was positively regulated by tyrosine phosphorylation in some cells, whereas the lipoxygenase activity of leukocytes was negatively regulated, at least in part, by tyrosine phosphorylation. Ulcerative colitis (UC) is an inflammatory disease of unknown etiology. The role of soluble mediators that amplify and modulate the inflammatory response in this disease has generated great interest, with emphasis being placed on the role played by arachidonic acid metabolites (3). Many in vitro studies have demonstrated an increased arachidonic acid content in the colonic mucosa of U C patients and an increase in the prostaglandin and leukotriene contents of U C biopsy specimens and rectal mucosal cultures, respectively (4-6). Many compounds that stimulate arachidonic acid metabolism also affect PTK. It thus seemed worthwhile to us to determine the PTK activity in the inflamed colonic mucosa
of U C patients. In this study we examined the PTK activity in the cytosolic and particulate fractions of colonic mucosal homogenates obtained from U C patients and normal controls. MATERIALS AND METIIODS
Subjects All patients gave informed consent for this study, which was also approved by the Institutional Ethical Committee. The subjects were 12 patients with UC and 12 with colon cancer who underwent surgery at the Second Dept. of Surgery at Hyogo College of Medicine between October 1988 and August 1990. Mucosal samples Inflamed colonic mucosal samples were obtained from the 12 patients with UC, who included 6 women and 6 men with a mean age of 26 years (range, 13-42 years). All patients had extensive disease and were receiving treatment with prednisolone at the time of surgery. The mean duration of disease was 7 years in this group (range, 2-11 years). Histologically normal mucosal samples were obtained from the 12 patients with colon cancer, who included 6 women and 6 men with a mean age of 54 years (range, 4968 years). None of these were receiving any treatment with steroids or other anti-inflammatory drugs, and this group served as controls.
PTK Activity in Ulcerative Colitis
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