Secretory leukocyte proteinase inhibitor, alpha-1-antitrypsin deficiency and emphysema: Preliminary study, speculation and an hypothesis

Role of elastases in the pathogenesis of chronic obstructive pulmonary disease: implications for treatment

Neutrophil elastase, metalloproteinases, and their inhibitors play an important role in the development of chronic obstructive pulmonary disease (COPD), resulting in extensive tissue damage and malfunctioning of the airways. Nearly fifty years after the protease-antiprotease imbalance hypothesis has been suggested for the cause of emphysema, it is still appealing, but it does not explain the considerable variation in the clinical expressions of emphysema. However, there are many recent research findings to support the imbalance hypothesis as will be shown in this review. Although limited, there might be openings for the treatment of the disease.

Paracrine factors of multipotent stromal cells ameliorate lung injury in an elastase-induced emphysema model

Multipotent stromal cells (MSCs) ameliorate several types of lung injury. The differentiation of MSCs into specific cells at the injury site has been considered as the important process in the MSC effect. However, although MSCs reduce destruction in an elastase-induced lung emphysema model, MSC differentiation is relatively rare, suggesting that MSC differentiation into specific cells does not adequately explain the recuperation observed. Humoral factors secreted by MSCs may also play an important role in ameliorating emphysema. To confirm this hypothesis, emphysema was induced in the lungs of C57BL/6 mice by intratracheal elastase injection 14 days before intratracheal MSC or phosphate-buffered saline (PBS) administration. Thereafter, lungs were collected at several time points and evaluated. Our results showed that MSCs reduced the destruction in elastase-induced emphysema. Furthermore, double immunofluorescence staining revealed infrequent MSC engraftment and differentiation into epithelial cells. Real-time PCR showed increased levels of hepatocyte growth factor (HGF) and epidermal growth factor (EGF). Real-time PCR and western blotting showed enhanced production of secretory leukocyte protease inhibitor (SLPI) in the lung. In-vitro coculture studies confirmed the in vivo observations. Our findings suggest that paracrine factors derived from MSCs is the main mechanism for the protection of lung tissues from elastase injury.

SLPI and elafin: one glove, many fingers

Elafin and SLPI (secretory leucocyte protease inhibitor) have multiple important roles both in normal homoeostasis and at sites of inflammation. These include antiprotease and antimicrobial activity as well as modulation of the response to LPS (lipopolysaccharide) stimulation. Elafin and SLPI are members of larger families of proteins secreted predominantly at mucosal sites, and have been shown to be modulated in multiple pathological conditions. We believe that elafin and SLPI are important molecules in the controlled functioning of the innate immune system, and may have further importance in the integration of this system with the adaptive immune response. Recent interest has focused on the influence of inflamed tissues on the recruitment and phenotypic modulation of cells of the adaptive immune system and, indeed, the local production of elafin and SLPI indicate that they are ideally placed in this regard. Functionally related proteins, such as the defensins and cathelicidins, have been shown to have direct effects upon dendritic cells with potential alteration of their phenotype towards type I or II immune responses. This review addresses the multiple functions of elafin and SLPI in the inflammatory response and discusses further their roles in the development of the adaptive immune response.

Alpha1-antitrypsin deficiency in 26-year-old subjects: lung, liver, and protease/protease inhibitor studies

BACKGROUND

Clinical and biochemical signs of lung and liver disease have been followed prospectively in a birth cohort of individuals with alpha1-antitrypsin (AAT) deficiency.

OBJECTIVE

At age 26 years, the focus was on clinical health, lung and liver function tests, and plasma markers of the protease/antiprotease balance. The effect of early childhood environment and symptoms was also studied.

METHODS

Eligible individuals were 26-year-old subjects with AAT deficiency (PiZ, n = 122; PiZ -, n = 2; PiSZ/S-, n = 53) and control subjects (PiMM, n = 44). Of the original AAT-deficient subjects, 119 completed the clinical examination and 134 answered the questionnaire.

RESULTS

The prevalence of respiratory symptoms did not differ between the PiZ and SZ groups. Sixteen percent of PiZ and 14% of PiSZ subjects had asthma. Four current smokers (67%) and 22% of ex-smokers/never-smokers reported recurrent wheezing (p = 0.03). No difference in FEV1 or FEV1/FVC ratio was found between the PiZ, SZ (5% being smokers), and MM individuals (all nonsmokers). A decreased FEV1/FVC ratio was found in PiZ subjects with neonatal cholestasis, compared to remaining PiZ subjects (p = 0.02). Recurrent wheezers at age 2 years with AAT deficiency had decreased FEV1/FVC ratio (p = 0.025) at age 26 years. None had clinical symptoms of liver disease. Six percent of PiZ and 9% of PiSZ subjects had a marginal increase of serum alanine aminotransferase; 7% of PiZ and 4% of PiSZ had abnormal gamma-glutamyl transferase test results. The PiZ and SZ individuals had decreased plasma albumin (p = 0.0002). Secretory leukocyte protease inhibitor (SLPI) was increased in PiZ and SZ subjects compared to PiMM subjects (p = 0.0001). Neutrophil lipocalin was decreased in PiZ subjects (p = 0.0004) and PiSZ subjects (p = 0.001) compared to PiMM individuals. The elastase/AAT complex concentration was lower in AAT-deficient subjects (p = 0.0001).

CONCLUSION

Twenty-six-year-old PiZ and SZ individuals (5% smokers) had normal lung function test results, and 4 to 9% had marginal deviations in liver test results. Analyses of SLPI and neutrophil lipocalin, a marker of neutrophil activity, indicate compensatory changes in the AAT-deficiency state.