Isoaspartate, carbamoyl phosphate synthase-1, and carbonic anhydrase-III as biomarkers of liver injury

We had previously shown that alcohol consumption can induce cellular isoaspartate protein damage via an impairment of the activity of protein isoaspartyl methyltransferase (PIMT), an enzyme that triggers repair of isoaspartate protein damage. To further investigate the mechanism of isoaspartate accumulation, hepatocytes cultured from control or 4-week ethanol-fed rats were incubated in vitro with tubercidin or adenosine. Both these agents, known to elevate intracellular S-adenosylhomocysteine levels, increased cellular isoaspartate damage over that recorded following ethanol consumption in vivo. Increased isoaspartate damage was attenuated by treatment with betaine. To characterize isoaspartate-damaged proteins that accumulate after ethanol administration, rat liver cytosolic proteins were methylated using exogenous PIMT and (3)H-S-adenosylmethionine and proteins resolved by gel electrophoresis. Three major protein bands of ∼ 75-80 kDa, ∼ 95-100 kDa, and ∼ 155-160 kDa were identified by autoradiography. Column chromatography used to enrich isoaspartate-damaged proteins indicated that damaged proteins from ethanol-fed rats were similar to those that accrued in the livers of PIMT knockout (KO) mice. Carbamoyl phosphate synthase-1 (CPS-1) was partially purified and identified as the ∼ 160 kDa protein target of PIMT in ethanol-fed rats and in PIMT KO mice. Analysis of the liver proteome of 4-week ethanol-fed rats and PIMT KO mice demonstrated elevated cytosolic CPS-1 and betaine homocysteine S-methyltransferase-1 when compared to their respective controls, and a significant reduction of carbonic anhydrase-III (CA-III) evident only in ethanol-fed rats. Ethanol feeding of rats for 8 weeks resulted in a larger (∼ 2.3-fold) increase in CPS-1 levels compared to 4-week ethanol feeding indicating that CPS-1 accumulation correlated with the duration of ethanol consumption. Collectively, our results suggest that elevated isoaspartate and CPS-1, and reduced CA-III levels could serve as biomarkers of hepatocellular injury.

Analytical and clinical performance of a fully automated cardiac multi-markers strategy based on protein biochip microarray technology

OBJECTIVES

The analytical and clinical performance of the Evidence Cardiac Panel were evaluated.

DESIGN AND METHODS

The Evidence Cardiac Panel, an automated protein biochip microarray system, allows the simultaneous determination of creatine kinase MB (CK-MB), myoglobin (MYO), glycogen phosphorylase BB (GPBB), heart-type fatty acid-binding protein (H-FABP), carbonic anhydrase III (CA III), cardiac troponin I (cTnI). Precision: 3 levels of quality control (QC) and 2 in house pools (P) were assayed. Method comparison: MYO and cTnI concentrations measured on Evidence (E) and on Dimension RxL (D) analyzers were compared. Clinical study: 132 non-consecutive patients admitted to the Emergency Department for chest pain were enrolled.

RESULTS AND CONCLUSIONS

The between-day imprecision was CK-MB=6.80-10.08%; MYO=5.36-16.50%; GPBB=6.51-12.12%; H-FABP=6.26-12.63%; CA III=6.98-13.61%; cTnI=6.02-9.80%. Method comparison: E-MYO vs. D-MYO, Bias=-29.22, 95% CI from -40.25 to -18.18; E-cTnI vs. D-cTnI, Bias=-2.75, 95% CI from -4.04 to -1.46. In patients studied (at discharge: AMI, acute myocardial infarction n=42; non-AMI, n=90) H-FABP showed the highest accuracy (ROC analysis, AUC=0.92) and "cTnI+H-FABP" the greatest diagnostic efficacy (89.4%) in AMI diagnosis.

Direct chemiluminescent imaging detection of Cu/Zn-superoxidase dismutase, glutathione peroxidase, carbonic anhydrase-III, and catalase in rat liver cytosol separated by native porous gradient polyacrylamide gel electrophoresis

The cytosolic enzymes extracted from rat hepatocytes were separated by native porous gradient-PAGE (PG-PAGE) and were detected with a sensitive and fast chemiluminescence (CL) imaging method. Several peroxidases including glutathione peroxidase, Cu/Zn-superoxidase dismutase, and some other metallo-enzymes such as catalase, carbonic anhydrase-III (CA-III) present in the cytosol of rat hepatocytes have been selectively and sensitively detected by the direct CL imaging method using the luminol-H(2)O(2) chemiluminescent reagents. All detections after PG-PAGE were completed within 9 min. The linear range for the typical metallo-enzyme, e.g., CA-III is 0.75-4.9 microg/mL, with a detection limit of 0.25 microg/mL. In comparison with the traditional CBB-R250 staining method, the detection period decreased about 70 times and the detection sensitivity improved over ten times. Furthermore, two enzymes present in rat liver cytosol were identified employing MALDI-MS analysis of the tryptic digest after PG-PAGE.

Mechanisms underlying the effects of inulin-type fructans on calcium absorption in the large intestine of rats

Inulin-type fructans (inulin, oligofructose, fructooligosaccharides) in the diet do increase intestinal calcium absorption in animals and humans, but the underlying mechanism has not been identified. We therefore assessed the effects of fermentation of inulin-type fructans on transepithelial calcium transport in rat large intestine. Transepithelial calcium fluxes in vitro (Ussing chamber), effects on gene expression, mucosal morphology, and composition of luminal contents were determined in rats fed a standard diet and/or a diet containing 10% (w/w) 1/1 inulin-oligofructose mixture (INOF). Net transepithelial calcium transport in large intestine of rats fed a standard diet was increased by high mucosal calcium concentrations, the presence of 100 mmol/L mucosal short-chain fatty acids (SCFAs), the presence of 10 g/L INOF at the mucosal side, but not by reducing mucosal pH. Tissues from rats fed INOF did not show altered calcium transport when compared to controls. However, when flux data were based on the total caecal surface area, INOF-fed rats nearly doubled absorption rate in caecum. INOF feeding altered transcript levels of several mucosal genes that can be linked to transcellular and paracellular calcium transport processes. In addition, a decreased luminal pH in caecum with markedly increased caecal pools of total, soluble, and ionized calcium resulted from INOF ingestion. Thus, inulin-type fructans increase the large intestinal calcium absorption by different mechanisms including enhanced pools of soluble and ionized calcium, an increase in the absorptive surface predominantly in caecum, the increased concentrations of SCFAs, and by direct interaction with the intestinal tissue.

The mouse liver content of carbonic anhydrase III and glutathione S-tranferases A3 and P1 depend on dietary supply of methionine and cysteine

The contents of glutathione S-transferase (GST) subunits, carbonic anhydrase III (CAIII), glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and a 230 kDa protein are affected by protein deprivation in mouse liver. In order to know if particular amino acids control these contents, the effects of feeding for 5 days with diets containing different amino acids were examined. After an exploration using SDS-PAGE analysis, the action of selected diets was further examined by distinct techniques. The 230 kDa protein was identified as fatty acid synthase (FAS) by both mass spectrometry and amino acid sequence analyses. Dietary tests showed that: (1) a protein-free diet (PFD) increased the content of glutathione S-transferases P1 and M1, and glyceraldehyde-3-phosphate dehydrogenase, while the content of glutathione S-transferase A3, fatty acid synthase and carbonic anhydrase III decreased; (2) a protein-free diet having either methionine or cysteine preserved the normal contents of glutathione S-transferases P1, A3, M1 and carbonic anydrase III; (3) a protein-free diet having threonine preserved partially the normal contents of glutathione S-transferases P1, A3, M1 and carbonic anhydrase III; (4) a protein-free diet having methionine, threonine and cysteine prevented in part the loss of fatty acid synthase; and (5) the glyceraldehyde-3-phosphate dehydrogenase content was controlled by increased carbohydrate level and/or by lower amino acid content of diets, but not by any specific amino acid. These data indicate that methionine and cysteine exert a main role on the control of liver glutathione S-transferases A3 and P1, and carbonic anhydrase III. Thus, they emerge necessary to prevent unsafe alterations of liver metabolism caused by protein deprivation.

Pepsin and Carbonic Anhydrase Isoenzyme III as Diagnostic Markers for Laryngopharyngeal Reflux Disease

OBJECTIVES/HYPOTHESIS

The objective was to investigate the potential use of pepsin and carbonic anhydrase isoenzyme III (CA-III) as diagnostic markers for laryngopharyngeal reflux disease.

STUDY DESIGN

Prospective cell biological investigation was conducted of laryngeal biopsy specimens taken from 9 patients with laryngopharyngeal reflux disease and 12 normal control subjects using antibodies specific for human pepsin (produced in the authors' laboratory within the Department of Otolaryngology at Wake Forest University Health Sciences, Winston-Salem, NC) and CA-III.

METHODS

Laryngeal biopsy specimens were frozen in liquid nitrogen for Western blot analysis and fixed in formalin for pepsin immunohistochemical study. Specimens between two groups (patients with laryngopharyngeal reflux disease and control subjects) were compared for the presence of pepsin. Further analyses investigated the correlation between pepsin, CA-III depletion, and pH testing data.

RESULTS

Analysis revealed that the level of pepsin was significantly different between the two groups (P < .001). Secondary analyses demonstrated that presence of pepsin correlated with CA-III depletion in the laryngeal vocal fold and ventricle (P < .001) and with pH testing data in individuals with laryngopharyngeal reflux disease.

CONCLUSION

Pepsin was detected in 8 of 9 patients with laryngopharyngeal reflux disease, but not in normal control subjects (0 of 12). The presence of pepsin was associated with CA-III depletion in the laryngeal vocal fold and ventricle. Given the correlation between laryngopharyngeal reflux disease and CA-III depletion, it is highly plausible that CA-III depletion, as a result of pepsin exposure during laryngopharyngeal reflux, predisposes laryngeal mucosa to reflux-related inflammatory damage.

Isolation and measurement of carbonic anhydrase isoenzyme III in plasma, sera, and tissues of dogs

OBJECTIVE

To purify canine carbonic anhydrase isoenzyme III (CA-III) and determine plasma, serum, and tissue concentrations of CA-III in healthy dogs and dogs with experimentally induced muscle damage.

ANIMALS

121 healthy Beagles.

PROCEDURE

Muscle was obtained from 2 Beagles after euthanasia, and CA-III was purified and characterized by use of column chromatography and electrophoresis, respectively. A CA-III-specific ELISA was developed to determine concentrations of CA-III in plasma of 116 dogs and tissues of 1 dog. Serum creatine kinase (CK) activity and CA-III concentration were also determined before and after induction of muscle damage by IM injection of 2 ml of 10% lidocaine to 2 dogs.

RESULTS

Canine CA-III had a molecular weight of 28 kd and an isoelectric point of 8.2. Mean (+/- SD) concentration of CA-III in plasma of healthy dogs was 16.91 +/- 9.55 ng/ml. The highest tissue concentration of CA-III was detected in skeletal muscle. Serum concentration of CA-III increased and peaked within the first 2 to 3 hours after induction of muscle damage. The increase in CA-III concentration was more rapid than that of CK activity, and concentration reached its maximum and returned to baseline sooner than did CK activity.

CONCLUSIONS AND CLINICAL RELEVANCE

The CA-III ELISA we developed was a sensitive method for determining CA-III concentrations in plasma, serum samples, and tissue specimens of dogs. Use of this ELISA requires only a small volume of serum and may enable the study of changes in CA isoenzyme concentrations associated with muscle disorders in dogs.

Detection and identification of subcutaneous adipose tissue protein related to obesity in New Zealand obese mouse

New Zealand obese (NZO) mouse, a genetic model of obesity, shows hyperphagia, hyperinsulinemia and leptin resistance. We analyzed subcutaneous adipose tissue proteins in NZO mice with a two-dimensional gel electrophoresis technique followed by protein sequence analysis. NZO mice showed hyperinsulinemia and hyperleptinemia. Abdominal subcutaneous adipose tissue was inspected in NZO and C57BL/6J lean mice. Two-dimensional gel electrophoresis detected 4 spots which were obviously reduced in NZO mice. Those spots were p26, p19, p18 and p15. Internal sequences of the p26 and p15 protein were homologous with those of carbonic anhydrase III, p19 was cytochrome b5, p18 was superoxide dismutase. Serum arachidonic acid level in NZO mice was lower by 80% of C57BL/6J mice. The present study demonstrated the reduction of several enzymes related to lipid metabolism in NZO mice. These data raises the hypothesis that the supposed changes of membrane fluidity caused by altered membrane lipid content may involve central leptin resistance of this model of obesity.