Urinary Bikunin Determination Provides Insight into Proteinase/Proteinase Inhibitor Imbalance in Patients with Inflammatory Diseases

Abstract

Bikunin (BK) is a Kunitz-type proteinase inhibitor responsible for most of the antitryptic activity of urine and so is known as the urinary trypsin inhibitor. As its excretion increases in inflammatory conditions, it is often considered to be a positive acute phase protein (APP). However, the gene for BK is downregulated in inflammation. In human plasma the major part of BK is covalently linked through a glycosaminoglycan chain to one or two homologous peptide heavy chains, thus forming high molecular weight proteinase inhibitors called pre-alpha-inhibitor (PalphaI) and inter-alpha-inhibitor (IalphaI), respectively. The C-terminal parts of these heavy chains are very sensitive to proteolysis. Neutrophil proteinases in particular are able to release from IalphaI and PalphaI BK (M, about 25,000) which retains its antitryptic activity and is quickly excreted in urine. It was therefore an early supposition that the higher urinary excretion of BK occurring during inflammatory diseases should be, at least in some respect, related to a partial proteolysis of IalphaI and PalphaI. In this study we observed that BK, determined as antitryptic activity, was clearly increased in urine from 35 patients with inflammatory diseases varying in origin and severity (76.5 +/- 75.5 IU/g vs. reference value <10 IU/g creatinine). This increase seems mainly to be associated with polymorphonuclear leukocyte activation, monitored by human leukocyte elastase (HLE) determination rather than with the acute phase response assessed by C-reactive protein (CRP) measurement. For all the patients we found that the urinary levels of BK and serum concentration of intact IalphaI correlated inversely (r=-0.36; p=0.03), in agreement with the presumed precursor-product relationship linking IalphaI and BK. We also proved that urinary BK was significantly higher, and serum IalphaI was significantly lower, in samples with plasma HLE values above the reference: 90 microg/l. Taken together, our results demonstrate that BK, the urinary excretion of which is increased in inflammatory conditions, originates, at least partly, from IalphaI and PalphaI by proteolytic cleavage. Consequently, urinary BK determination provides information on the severity of systemic proteolysis occurring in inflammation. We also demonstrated that during inflammatory diseases IalphaI and PalphaI concentrations in serum are dependent on their increased utilization as well as on the regulation of their biosynthesis.

Proteomics of exhaled breath: methodological nuances and pitfalls

“…Bikunin excretion increases in inflammatory conditions and is often considered to be a positive acute phase protein. It was demonstrated that during inflammatory diseases, concentrations of serum high molecular weight bikunin products are dependent on their rate of utilization as well as on regulation of their biosynthesis (21).…”

Increased serum concentration of urinary trypsin inhibitor with asthma exacerbation

“…Several proteins are known to inactivate NE activity and NE degrades the pre-a-/inter-a-trypsin inhibitors, proteinase inhibitors, that release UTI [14,15]. UTI has been reported to be a positive acute phase protein whose concentration in serum and excretion in urine is increased in proportion to the invasiveness of the various diseases and the activation of neutrophils [17,18]. Previous study showed that both NE and UTI concentrations in BAL fluid of acute respiratory distress syndrome are significantly elevated, but only UTI concentration is significantly high in the serum [20].…”

“…Assay of urinary trypsin inhibitor, neutrophil elastase, a 1 -antitrypsin, tissue inhibitor of metalloproteinase-1 and matrix metalloproteinase-2 Serum UTI was determined by sandwich-type one-step enzyme immunoassay using polyclonal antibodies to human trypsin inhibitor [14,17,18] and a human assay kit (Mochida Pharmaceutical Co. Ltd., Tokyo, Japan). The ELISA procedure makes it possible to specifically measure UTI by trapping pre-a-/inter-a-inhibitors in solid phase with a treatment of perchloric acid.…”

Proteomic analysis of exhaled breath condensate for diagnosis of pathologies of the respiratory system

“…Тяжесть заболевания 0/3/10/4 * 2/4/2/3/2 ** *** (рисунок). Показано, что альфа-1-микроглобулин ингибирует иммунные функции лейкоцитов in vitro и его распределение связывают с защитной и противовоспалительной ролью in vivo [10], а репрессия бикунина характерна для воспаления [11]. Эти данные позволяют предположить, что острое воспаление, сопровождающее как ХОБЛ, так и пневмонию, может вызывать снижение уровня экспрессии предшественника альфа-1-микроглобулина/бикунина.…”