Secretory Leukocyte Protease Inhibitor Levels Research Articles

Salivary Concentration of Secretory Leukocyte Protease Inhibitor, an Antimicrobial Protein, Is Decreased with Advanced Age

Background: Secretory leukocyte protease inhibitor (SLPI) exhibits antimicrobial activities that, in addition to other well-characterized proteins such as lysozyme and lactoferrin, is thought to play a critical role in mucosal defenses. Although elderly individuals are particularly susceptible to mucosal infections, salivary production of SLPI has not been assessed in an aged cohort. Objectives: Hypothesizing that oral SLPI concentrations are reduced with advanced age, this cross-sectional study compared SLPI concentrations to concentrations of lysozyme, lactoferrin and total protein in unstimulated salivary secretions of healthy, community-dwelling 79+-year-old and younger adults. Methods: Study participants were 45 non-hospitalized dentate adults aged 79–89 (23 elderly) or 21–51 years (22 non-elderly). Home-based interviews and clinical examinations determined dentate status and confirmed the absence of dentures, oral mucosal disease, anti-infective medication use, irradiation therapy for head and neck cancer and self-perceived xerostomia. Whole unstimulated saliva was collected from all subjects and analyzed for antimicrobial protein concentration by enzyme-linked immunosorbent assay and for total protein content by the bicinchoninic acid method. Bivariate and multivariate (generalized linear modeling) analyses evaluated the relationships between age, gender and salivary protein concentrations. Results: Mean salivary levels of SLPI and lysozyme were lower in elderly compared with non-elderly subjects (p < 0.001), unlike lactoferrin and total protein levels. Similar results were obtained when concentrations of the individual proteins were normalized to the total protein concentration, suggesting that glandular production of SLPI and lysozyme preferentially decreases with aging. Gender differences were detected only for SLPI concentrations; males had lower SLPI levels than females regardless of age (p < 0.01). Generalized linear models confirmed that age (p < 0.001) and gender (p < 0.05) were each associated with the SLPI concentration and together accounted for 50% of the variation in SLPI concentration in this population. Conclusion: These findings indicate that SLPI production is diminished among healthy community-dwelling older adults, particularly elderly males. Further investigation should determine the impact of decreased local SLPI production on the increased risk of oral mucosal disease with advanced age.

Endogenous mucosal antiviral factors of the oral cavity.

The oral cavity represents a unique site for mucosal transmission of human immunodeficiency virus type 1 (HIV-1). Unlike other mucosal sites, the oral cavity is rarely a site of HIV transmission despite detectable virus in saliva and oropharyngeal tissues of infected persons. One reason for this apparent paradox is the presence of endogenous mucosal antiviral factors. Innate inhibitory molecules, such as virus-specific antibodies, mucins, thrombospondin, and soluble proteins, have been identified and partially characterized from saliva. A recent addition to the growing list is secretory leukocyte protease inhibitor (SLPI), an approximately 12-kDa non-glycosylated protein found in serous secretions. Physiologic concentrations of SLPI potently protect adherent monocytes and activated peripheral blood mononuclear cells against HIV-1 infection. SLPI levels in saliva and semen but not breast milk approximate levels required for inhibition in vitro. Characterization of SLPI and other endogenous antiviral molecules may enhance our understanding of factors influencing mucosal HIV-1 transmission.

Induction of SLPI (ALP/HUSI-I) in Epidermal Keratinocytes

Secretory leukocyte protease inhibitor (SLPI) is a small, cationic protein that is known to be constitutively expressed by several glandular epithelia. SLPI inhibits leukocyte-derived proteinases, has anti-HIV-1, antibacterial, and anti-fungal properties, and interferes with the induction of synthesis of proinflammatory mediators in monocytes and macrophages. We now report that at both the mRNA and the protein level, SLPI shows inducible expression in a nonglandular epithelium. A weak expression of SLPI was found in the stratum granulosum of adult normal human epidermis; however, in lesional psoriatic epidermis and in migrating keratinocytes of healing wounds, a strong cytoplasmic staining was seen in the suprabasal keratinocytes. Remarkably, in the dermis adjacent to SLPI-expressing keratinocytes, SLPI was found extracellularly associated with elastin fibers, whereas the dermis in normal skin was negative. In cell culture, SLPI was hardly expressed in monolayers of proliferating keratinocytes. Differentiating cultures with a phenotype of normal skin expressed low levels of SLPI, whereas cultures with a regenerative/psoriatic phenotype expressed high levels. Functional studies with recombinant SLPI indicated that its antibacterial spectrum and potency are distinct from other anti-microbial peptides such as lysozyme and defensins. In view of the multiple functions of SLPI and the inducibility, we propose that it acts as an important first line defence mechanism in cutaneous injury.

Cysteine proteases of Trichomonas vaginalis degrade secretory leukocyte protease inhibitor.

Sexually transmitted diseases, including trichomoniasis, are risk factors for acquisition of human immunodeficiency virus (HIV) infection. Enhancement mechanisms are unknown. Secretory leukocyte protease inhibitor (SLPI) from saliva appears to prevent transmission of HIV through inhibition of virus entry into monocytic cells in vitro. This study was undertaken to determine if secreted cysteine proteases of Trichomonas vaginalis degrade SLPI and render it nonfunctional. It was determined if SLPI levels were decreased in vaginal fluids from pregnant women infected with T. vaginalis. Isolated proteases were incubated with recombinant human SLPI, and the degradation was followed by Western analysis with SLPI antiserum. SLPI levels were measured by ELISA in vaginal fluids from women infected with T. vaginalis and uninfected controls. Cysteine proteases cleaved SLPI and rendered it nonfunctional. Median levels of SLPI from infected patients were 26% of those of controls (P <.005). The degradation of SLPI in association with trichomonal infection may increase the risk of HIV acquisition.

Secretory leukocyte protease inhibitor (SLPI) in mucosal fluids inhibits HIV-I.

Despite the presence of HIV-1 in the oral cavity, transmission of the virus through saliva has not been proven. Consistent with these observations, we recently identified an endogenous 12 kD protein, secretory leukocyte protease inhibitor (SLPI), in saliva which blocks HIV-1 infection in vitro. Whereas other salivary proteins tested were inactive, purified native or recombinant SLPI inhibited HIV-1 infection of human monocytes at 100 ng ml-1. Levels of SLPI quantitated by ELISA in saliva from control and HIV-1 infected individuals exceeded this level, consistent with in vivo antiviral activity. As in saliva, levels of SLPI mRNA determined by Northern hybridization, and protein as assessed by immunohistochemistry in the salivary glands of control and infected populations were comparable. In contrast to adults, oral transmission occurs in infants, possibly due to their lack of fully developed salivary glands. To determine whether the inadequate antiviral protection might be compensated for by maternal sources, we evaluated breast milk samples obtained 6 months postpartum. Levels of SLPI were significantly lower than in saliva and not sufficient to provide antiviral protection in contrast to colostrum samples in which SLPI levels were equivalent to those in saliva and able to inhibit HIV-1 infection when tested in vitro. These data suggest that breast milk may provide transient antiviral activity in the newborn, but that this maternal source of SLPI is of insufficient duration to maintain protection against mucosal transmission of the virus over time. The high functional levels of SLPI in saliva and the low levels in mature breast milk correlate with negligible rates of HIV-1 transmission by saliva and higher rates by breast feeding.

歯周病り患部位におけるｓｅｃｒｅｔｏｒｙ ｌｅｕｋｏｃｙｔｅ ｐｒｏｔｃａｓｅ ｉｎｈｉｂｉｔｏｒ（ＳＬＰＩ）の動態

The present investigation was designed to clarify the possible relationship between the secretory leukocyte protease inhibitor (SLPI) in gingival crevicular fluid (GCF) and the periodontal clinical parameters or the presence of periodontopathic bacteria in subgingival plaque.SLPI levels in GCF were determined with a commercially available ELISA system and the neutrophil elastase (NE) activity in GCF was measured with a low molecular weight substrate S-2484. Subgingival plaque samples were tested for the presence of eight periodontopathic bacteria by DNA probe analysis.In thirty two examined sites from ten patients with periodontal maintenance care, the SLPI levels were positively associated with the GCF volume and the presence of gingival inflammation. Statistically significant negative correlations were found between SLPI levels and the presence of Porphyromonas gingivalis and Treponema denticola, whereas, the NE activity increased in the presence of the bacteria.The results demonstrated that the bacteria with the capacity to produce proteolytic enzymes degraded or inactivated the protease inhibitor, suggesting that the proteolytic damage of periodontal tissue might be caused by the decrease of active protease inhibitor.

Localization of immunoreactive secretory leukocyte protease inhibitor (SLPI) in intestinal mucosa.

Secretory leukocyte protease inhibitor (SLPI) is the dominant protease inhibitor in the mucus secretions of the repiratory and genital tracts, and local production seems likely, as immunoreactive SLPI has been found in the corresponding mucosa. To our knowledge, SLPI has not been previously demonstrated in intestinal epithelia or secretions. In an earlier study, however, we found surprisingly high levels of SLPI in peritonitis exudate from patients with gastrointestinal perforations. This study extends these observations by demonstrating the presence of immunoreactive SLPI in intestinal mucosa. In the small intestine, SLPI was present in Paneth cells and in scattered mucosa cells of goblet-type. In normal mucosa of the large bowel, SLPI was also found in scattered cells of goblet-type in the epithelium. In addition, immunoreactive SLPI was frequently found in colonic adenomas. The findings in this study raise several interesting questions on the possible role of SLPI in the gut epithelial defense against inflammatory assaults.

The elimination of secretory leukocyte protease inhibitor (SLPI) after intravenous injection in dog and man

After an intravenous injection of 35Sulphur-labelled secretory leukocyte protease inhibitor (SLPI) in four dogs, there was a rapid initial clearance (half-life 10 min) of radioactivity and immunoreactive SLPI from plasma. Later, the immunoreactive SLPI cleared more rapidly (T1/2 = 60 min) than the radioactivity, indicating the gradual appearance of radioactive degradation products. Intact recombinant human SLPI as well as radioactive fragments appeared in the urine. The urinary excretion of radioactivity during the first 3 h was less than 10% of the injected dose. After killing at 3 h, the kidneys contained more radioactivity per gram tissue than the other parenchymatous organs.Following an intravenous injection of l25Iodine-labelled native SLPI in three human volunteers, a rapid initial clearance of both protein-bound and total plasma radioactivity (half-life 10 min) was seen. Later, the protein-bound radioactivity cleared slower (half-life 120 min) than the total radioactivity, indicating a progressive degradation of SLPI with release of radioactive fragments to plasma. After 54 h 80-96% of the radioactivity had been excreted in the urine, mainly as free l25Iodine. No intact SLPI was found in the urine. A renal metabolism of SLPI is assumed, which is supported also by the finding of elevated serum levels of SLPI in uraemic patients. The possible therapeutic use of SLPI is briefly discussed.

The elimination of secretory leukocyte protease inhibitor (SLPI) after intravenous injection in dog and man

After an intravenous injection of 35Sulphur-labelled secretory leukocyte protease inhibitor (SLPI) in four dogs, there was a rapid initial clearance (half-life 10 min) of radioactivity and immunoreactive SLPI from plasma. Later, the immunoreactive SLPI cleared more rapidly (T1/2 = 60 min) than the radioactivity, indicating the gradual appearance of radioactive degradation products. Intact recombinant human SLPI as well as radioactive fragments appeared in the urine. The urinary excretion of radioactivity during the first 3 h was less than 10% of the injected dose. After killing at 3 h, the kidneys contained more radioactivity per gram tissue than the other parenchymatous organs. Following an intravenous injection of 125Iodine-labelled native SLPI in three human volunteers, a rapid initial clearance of both protein-bound and total plasma radioactivity (half-life 10 min) was seen. Later, the protein-bound radioactivity cleared slower (half-life 120 min) than the total radioactivity, indicating a progressive degradation of SLPI with release of radioactive fragments to plasma. After 54 h 80-96% of the radioactivity had been excreted in the urine, mainly as free 125Iodine. No intact SLPI was found in the urine. A renal metabolism of SLPI is assumed, which is supported also by the finding of elevated serum levels of SLPI in uraemic patients. The possible therapeutic use of SLPI is briefly discussed.