Alpha 1-antitrypsin deficiency and chronic pancreatitis

Alpha-1-antitrypsin deficiency: Genetic variations, clinical manifestations and therapeutic interventions

Alpha-1-antitrypsin (AAT) is an acute phase secretory glycoprotein that inhibits neutrophil proteases like elastase and is considered as the archetype of a family of structurally related serine-protease inhibitors termed serpins. Serum AAT predominantly originates from liver and increases three to five fold during host response to tissue injury and inflammation. The AAT deficiency is unique among the protein-misfolding diseases in that it causes target organ injury by both loss-of-function and gain-of-toxic function mechanisms. Lack of its antiprotease activity is associated with premature development of pulmonary emphysema and loss-of-function due to accumulation of resultant aggregates in chronic obstructive pulmonary disease (COPD). This' in turn' markedly reduces the amount of AAT that is available to protect lungs against proteolytic attack by the enzyme neutrophil elastase. The coalescence of AAT deficiency, its reduced efficacy, and cigarette smoking or poor ventilation conditions have devastating effect on lung function. On the other hand, the accumulation of retained mutant proteins in the endoplasmic reticulum of hepatocytes in a polymerized form rather than secreted into the blood in its monomeric form is associated with chronic liver disease and predisposition to hepatocellular carcinoma (HCC) by gain- of- toxic function. Liver injury resulting from this gain-of-toxic function mechanism in which mutant AAT retained in the ER initiates a series of pathologic events, eventually culminating at liver cirrhosis and HCC. Here in this review, we underline the structural, genetic, polymorphic, biochemical and pathological advances made in the field of AAT deficiency and further comprehensively emphasize on the therapeutic interventions available for the patient.

Detection of Cancer-Specific Proteases Using Magnetic Relaxation of Peptide-Conjugated Nanoparticles in Biological Environment

Protease expression is closely linked to malignant phenotypes of different solid tumors; as such, their detection is promising for diagnosis and treatment of cancers, Alzheimer's, and vascular diseases. Here, we describe a new method for detecting proteases by sensitively monitoring the magnetic relaxation of monodisperse iron oxide nanoparticles (IONPs) using magnetic particle spectrometer (MPS). In this assay, tailored peptides functioning as activatable nanosensors link magnetic nanoparticles and possess selective sites that are recognizeable and cleaveable by specific proteases. When these linker peptides, labeled with biotin at N- and C-terminals, are added to the neutravidin functionalized IONPs, nanoparticles aggregate, resulting in well-defined changes in the MPS signal. However, as designed, in the presence of proteases these peptides are cleaved at predetermined sites, redispersing IONPs, and returning the MPS signal(s) close to its preaggregation state. These changes observed in all aspects of the MPS signal (peak intensity, its position as a function of field amplitude, and full width at half-maximum-when combined, these three also eliminate false positives), help to detect specific proteases, relying only on the magnetic relaxation characteristics of the functionalized nanoparticles. We demonstrate the general utility of this assay by detecting one each from the two general classes of proteases: trypsin (digestive serine protease, involved in various cancers, promoting proliferation, invasion, and metastasis) and matrix metalloproteinase (MMP-2, observed through metastasis and tumor angiogenesis). This MPS based protease-assay is rapid, reproducible, and highly sensitive and can form the basis of a feasible, high-throughput method for detection of various other proteases.

Hepatic steatosis depresses alpha-1-antitrypsin levels in human and rat acute pancreatitis

Hepatic steatosis (HS) can exacerbate acute pancreatitis (AP). This study aimed to investigate the relation between α1-antitrypsin (AAT) and acute pancreatitis when patients have HS. Using proteomic profiling, we identified 18 differently expressed proteins pots in the serum of rats with or without HS after surgical establishment of AP. AAT was found to be one of the significantly down-regulated proteins. AAT levels were significantly lower in hepatic steatosis acute pancreatitis (HSAP) than in non-HSAP (NHSAP) (P < 0.001). To explore the clinical significance of these observations, we measured the levels of AAT in the serum of 240 patients with HSAP, NHSAP, fatty liver disease (FLD), or no disease. Compared with healthy controls, serum AAT levels in patients with NHSAP were significantly higher (P < 0.01), while in patients with HSAP serum AAT levels were significantly lower (P < 0.01). Further studies showed that acute physiology and chronic health evaluation (APACHE-II) scores were negatively correlated with serum AAT levels (r = −0.85, P < 0.01). In conclusion, low serum levels of AAT in patients with HSAP are correlated with disease severity and AAT may represent a potential target for therapies aiming to improve pancreatitis.

Scavenger receptor class B, type I-mediated uptake of A1AT by pulmonary endothelial cells

In addition to exerting a potent anti-elastase function, α-1 antitrypsin (A1AT) maintains the structural integrity of the lung by inhibiting endothelial inflammation and apoptosis. A main serpin secreted in circulation by hepatocytes, A1AT requires uptake by the endothelium to achieve vasculoprotective effects. This active uptake mechanism, which is inhibited by cigarette smoking (CS), involves primarily clathrin- but also caveola-mediated endocytosis and may require active binding to a receptor. Because circulating A1AT binds to high-density lipoprotein (HDL), we hypothesized that scavenging receptors are candidates for endothelial uptake of the serpin. Although the low-density lipoprotein (LDL) receptor-related protein 1 (LRP1) internalizes only elastase-bound A1AT, the scavenger receptor B type I (SR-BI), which binds and internalizes HDL and is modulated by CS, may be involved in A1AT uptake. Transmission electron microscopy imaging of colloidal gold-labeled A1AT confirmed A1AT endocytosis in both clathrin-coated vesicles and caveolae in endothelial cells. SR-BI immunoprecipitation identified binding to A1AT at the plasma membrane. Pretreatment of human lung microvascular endothelial cells with SR-B ligands (HDL or LDL), knockdown of SCARB1 expression, or neutralizing SR-BI antibodies significantly reduced A1AT uptake by 30-50%. Scarb1 null mice exhibited decreased A1AT lung content following systemic A1AT administration and reduced lung anti-inflammatory effects of A1AT supplementation during short-term CS exposure. In turn, A1AT supplementation increased lung SR-BI expression and modulated circulating lipoprotein levels in wild-type animals. These studies indicate that SR-BI is an important mediator of A1AT endocytosis in pulmonary endothelium and suggest a cross talk between A1AT and lipoprotein regulation of vascular functions.

Serum concentrations of canine alpha1-proteinase inhibitor in cobalamin-deficient Yorkshire Terrier dogs

Fecal canine alpha1-proteinase inhibitor (cα1-PI) concentration has been reported to be increased in dogs with protein-losing enteropathy due to the loss of cα1-PI into the gastrointestinal tract. A chronic loss of cα1-PI may theoretically deplete serum cα1-PI, potentially altering the proteinase-to-proteinase inhibitor balance. Protein-losing enteropathy has been reported to occur frequently in certain dog breeds such as Yorkshire Terriers and to be associated with hypocobalaminemia. The objective was to compare serum cα1-PI concentrations in Yorkshire Terriers with and without cobalamin (COB) deficiency. Serum samples from 52 COB-deficient and 69 normocobalaminemic Yorkshire Terriers, which had been submitted to the Gastrointestinal Laboratory (2008–2011; College Station, TX), were included retrospectively. Serum cα1-PI concentrations were measured using an in-house radioimmunoassay and compared between Yorkshire Terriers with and without COB deficiency using a Mann–Whitney U test. A Fisher exact test was used to evaluate whether a decreased serum cα1-PI concentration is associated with COB deficiency in Yorkshire Terriers. Serum cα1-PI concentrations were significantly lower in COB-deficient Yorkshire Terriers (median: 1,016 mg/l, range: 315–3,945 mg/l) than in normocobalaminemic Yorkshire Terriers (median: 1,665 mg/l, range: 900–2,970 mg/l; P < 0.0001). One-fourth ( n = 13) of the COB-deficient Yorkshire Terriers had a serum cα1-PI concentration below the lower limit of the reference interval (<732 mg/l), and COB deficiency was associated with decreased serum cα1-PI concentrations ( P < 0.0001). In the current study, serum cα1-PI concentrations are significantly lower in COB-deficient Yorkshire Terriers when compared to normocobalaminemic Yorkshire Terriers. Further studies are needed to determine the functional and potential prognostic implications of serum cα1-PI concentrations in dogs with gastrointestinal disease.

Role of proteases and antiprotease in the etiology of chronic pancreatitis

BACKGROUND/AIM

Chronic pancreatitis (CP) is the progressive and irreversible destruction of the pancreas characterized by the permanent loss of endocrine and exocrine function. Trypsin, the most important digestive enzyme plays a central role in the regulation of all other digestive enzymes. Chymotrypsin, an endopeptidase hydrolyzes peptides at amino acids with aromatic side chains. Alpha-1-antitrypsin is a principal antiprotease which protects the mucosal tissue from the proteolytic effects of trypsin and chymotrypsin by the formation of molar complexes. The present study is aimed at examining the role of proteases (trypsin and chymotrypsin) and anti-protease (α1-anti-trypsin) in the etiopathogenesis of chronic pancreatitis.

PATIENTS AND METHODS

A total of 90 CP patients and 110 age and sex matched controls were considered for the study. Serum trypsin, chymotrypsin and α1-anti-trypsin levels were determined prospectively in CP patients and compared to healthy controls as described previously.

RESULTS

The mean activity of trypsin were found to be increased in CP patients (X ± SD = 0.82 ± 0.838) in comparison to normal control group (X ± SD = 0.55 ± 0.328), (P = 0.001). Chymotrypsin activity were also found to be elevated in CP patients (X ± SD = 0.63 ± 0.278) in comparison to control group (X ± SD = 0.39 ± 0.295), (P = 0.0001). The mean α-1-anti-trypsin activity were found to be lowered in CP patients (X ± SD = 0.42 ± 0.494) in comparison to control group (X ± SD = 0.67 ± 0.465), with the variation being significant (P = 0.0003).

CONCLUSION

The findings suggest an imbalance in the synthesis and degradation of proteolytic enzymes and antiprotease indicating an altered aggressive and defensive role in the pathogenesis of chronic pancreatitis.

A review of α1-antitrypsin deficiency

α(1)-Antitrypsin (AAT) deficiency is an underrecognized genetic condition that affects approximately 1 in 2,000 to 1 in 5,000 individuals and predisposes to liver disease and early-onset emphysema. AAT is mainly produced in the liver and functions to protect the lung against proteolytic damage (e.g., from neutrophil elastase). Among the approximately 120 variant alleles described to date, the Z allele is most commonly responsible for severe deficiency and disease. Z-type AAT molecules polymerize within the hepatocyte, precluding secretion into the blood and causing low serum AAT levels (∼ 3-7 μM with normal serum levels of 20-53 μM). A serum AAT level of 11 μM represents the protective threshold value below which the risk of emphysema is believed to increase. In addition to the usual treatments for emphysema, infusion of purified AAT from pooled human plasma-so-called "augmentation therapy"-represents a specific therapy for AAT deficiency and raises serum levels above the protective threshold. Although definitive evidence from randomized controlled trials of augmentation therapy is lacking and therapy is expensive, the available evidence suggests that this approach is safe and can slow the decline of lung function and emphysema progression. Promising novel therapies are under active investigation.

The discovery of α1-antitrypsin and its role in health and disease

α1-Antitrypsin (AAT) is the archetype member of the serine protease inhibitor (SERPIN) supergene family. The AAT deficiency is most often associated with the Z mutation, which results in abnormal Z AAT folding in the endoplasmic reticulum of hepatocytes during biogenesis. This causes intra-cellular retention of the AAT protein rather than efficient secretion with consequent deficiency of circulating AAT. The reduced serum levels of AAT contribute to the development of chronic obstructive pulmonary disease (COPD) and the accumulation of abnormally folded AAT protein increases risk for liver diseases. In this review we show that with the discovery of AAT deficiency in the early 60s as a genetically determined predisposition to the development of early-onset emphysema, intensive investigations of enzymatic mechanisms that produce lung destruction in COPD were pursued. To date, the role of AAT in other than lung and liver diseases has not been extensively examined. Current findings provide new evidence that, in addition to protease inhibition, AAT expresses anti-inflammatory, immunomodulatory and antimicrobial properties, and highlight the importance of this protein in health and diseases. In this review co-occurrence of several diseases with AAT deficiency is discussed.

Survival prediction for pancreatic cancer patients receiving gemcitabine treatment

Although gemcitabine monotherapy is the standard treatment for advanced pancreatic cancer, patient outcome varies significantly, and a considerable number do not benefit adequately. We therefore searched for new biomarkers predictive of overall patient survival. Using LC-MS, we compared the base-line plasma proteome between 29 representative patients with advanced pancreatic cancer who died within 100 days and 31 patients who survived for more than 400 days after receiving at least two cycles of the same gemcitabine monotherapy. Identified biomarker candidates were then challenged in a larger cohort of 304 patients treated with the same protocol using reverse-phase protein microarray. Among a total of 45,277 peptide peaks, we identified 637 peaks whose intensities differed significantly between the two groups (p < 0.001, Welch's t test). Two MS peaks with the highest statistical significance (p = 2.6 x 10(-4) and p = 5.0 x 10(-4)) were revealed to be derived from alpha(1)-antitrypsin and alpha(1)-antichymotrypsin, respectively. The levels of alpha(1)-antitrypsin (p = 8.9 x 10(-8)) and alpha(1)-antichymotrypsin (p = 0.001) were significantly correlated with the overall survival of the 304 patients. We selected alpha(1)-antitrypsin (p = 0.0001), leukocyte count (p = 0.066), alkaline phosphatase (p = 8.3 x 10(-8)), and performance status (p = 0.003) using multivariate Cox regression analysis and constructed a scoring system (nomogram) that was able to identify a group of high risk patients having a short median survival time of 150 days (95% confidence interval, 123-187 days; p = 2.0 x 10(-15), log rank test). The accuracy of this model for prognostication was internally validated and showed good calibration and discrimination with a bootstrap-corrected concordance index of 0.672. In conclusion, an increased level of alpha(1)-antitrypsin is a biomarker that predicts short overall survival of patients with advanced pancreatic cancer receiving gemcitabine monotherapy. Although an external validation study will be necessary, the current model may be useful for identifying patients unsuitable for the standardized therapy.

[Exocrin pancreatic deficiency revealing an alpha-1-antitrypsin deficiency]

There are genetic mutations taking part in the physiopathology of pancreatitis. The role of alpha-1-antitrypsin (AAT) deficiency in this pathology is debated. We report the case of a 60-year-old man with a pancreatic exocrine insufficiency. He was diagnosed with AAT deficiency. The phenotype was Pi SZ, with genotyping confirmation. The place of AAT deficiency in the midst of pancreatic diseases should be further studied.

Alpha1-antitrypsin deficiency

Alpha1-antitrypsin deficiency is a genetic disorder that affects about one in 2000-5000 individuals. It is clinically characterised by liver disease and early-onset emphysema. Although alpha1 antitrypsin is mainly produced in the liver, its main function is to protect the lung against proteolytic damage from neutrophil elastase. The most frequent mutation that causes severe alpha1-antitrypsin deficiency arises in the SERPINA 1 gene and gives rise to the Z allele. This mutation reduces concentrations in serum of alpha1 antitrypsin by retaining polymerised molecules within hepatocytes: an amount below the serum protective threshold of 11 micromol/L increases risk for emphysema. In addition to the usual treatments for emphysema, infusion of purified alpha1 antitrypsin from pooled human plasma represents a specific treatment and raises the concentrations in serum and epithelial-lining fluid above the protective threshold. Evidence suggests that this approach is safe, slows the decline of lung function, could reduce infection rates, and might enhance survival. However, uncertainty about the cost-effectiveness of this expensive treatment remains.

Alpha 1-antitrypsin deficiency. 3: Clinical manifestations and natural history

A review of the clinical manifestations of alpha(1)-antitrypsin (AAT) deficiency, including lung disease and liver disease, and risk factors affecting the rate of decline in lung function in AAT deficient patients.

Trypsinogen gene mutations in patients with chronic or recurrent acute pancreatitis

Three-point mutations (R117H, N211, A16V) within the cationic trypsinogen gene have been identified in patients with hereditary pancreatitis (HP). A genetic background has also been discussed for idiopathic juvenile chronic pancreatitis (IJCP), which closely mimicks the clinical pattern of HP, and alcoholic chronic pancreatitis because only a small number of heavy drinkers develop pancreatitis. This prompted us to screen 104 patients in our well-defined pancreatitis cohort for the currently known cationic trypsinogen gene mutations. The R117H mutation was detected in seven patients (six patients of two clinically classified HP families, one patient with clinically classified IJCP) and the A16V mutation in one IJCP patient. No cationic trypsinogen gene mutations were found in the remaining 96 patients with chronic and recurrent acute pancreatitis of various etiologies. Our results demonstrate the need for genetic testing to exclude HP, particularly in the presence of an atypical or unknown family history. In addition, cationic trypsinogen gene mutations are no predisposing factor in patients with chronic and recurrent acute pancreatitis of different etiologies.