Clinical enzymology

Umbelliferon-α-d-glucopyranosyl-(2I→1II)-α-Dglucopyranoside ameliorates Diethylnitrosamine induced precancerous lesion development in liver via regulation of inflammation, hyperproliferation and antioxidant at pre-clinical stage

It is well documented that anomalous production of inflammatory proteins linked with most of the toxic expression and genesis of diverse chronic disease including cancer. Diethylnitrosamine (DEN) a well-known hepatotoxin and hepatocarcinogen, can induce oxidative stress and inflammatory reaction in it. Umbelliferone, secondary metabolites, is present in different plants and widely consumed by humans as medicine and food supplements. The aim of the current study was to scrutinize the chemoprotective potential of umbelliferon-α-d-glucopyranosyl-(2^I→1^II)-α-d-glucopyranoside (UFD) against DEN-induced hepatocellular carcinoma (HCC) in experimental rats. Single intraperitoneal injection of DEN (200mg/kg) was used for induction of HCC in rats and rats were grouped and orally treated with UFD (5, 10 and 20mg/kg) dose for 22 weeks. Parameters under investigation included hepatic, non-hepatic enzymes, oxidative stress, pro-inflammatory cytokines, COX-2 and NF-κB level along with histopathological examination in HCC rats. UFD exerted protective effect via reduction of oxidative stress, liver and non-liver parameters in a dose-dependent manner. It also reduced the expression of TNF-α, IL-1β, IL-6 and COX-2 in diseased rats. Our result revealed the essential repression of the inflammation cascade through modulation of nuclear factor-kappa B (NF-κB) signaling pathway.

Specific induction by glucocorticoids of steroid esterase in rat hepatic microsomes and its release into serum

Steroid esterase hydrolysing methylprednisolone 21-hemisuccinate was induced specifically and markedly in hepatic microsomes and serum of rats by various glucocorticoids. Among the glucocorticoids examined, dexamethasone and betamethasone showed the highest potency to induce the hepatic steroid esterase, the induction ratio being 32 and 33 times higher than the basal level (about 160 mU/g liver), respectively. Steroid esterase in the serum was induced greatly by fluocinolone acetonide and betamethasone to 92 and 79 times of the basal level of about 16 mU/mL, respectively, followed by dexamethasone and methylprednisolone. When dexamethasone was given to rats, the enzyme in other tissues except for duodenum and small intestine (of which activity was lowered to 50% of the basal level) was also elevated, but the induction ratio was much lower than that in the liver and serum. The induction of the steroid esterase is probably due to stimulation of de novo synthesis of the enzyme by glucocorticoids, because the elevation of esterase activity was inhibited by treatment with cycloheximide (a translation inhibitor) and actinomycin D (a transcription inhibitor), and about 4- and 10-hr lag time was observed before the elevation of esterase activity in liver and serum, respectively. Coupled with these observations the following results indicate that the steroid esterase in serum is probably synthesized in the liver and subsequently released into the blood via the Golgi apparatus: (1) when the liver of rats treated with dexamethasone was subjected to perfusion with a recycling system, significant amounts of steroid esterase were released into the perfusate; (2) anti-hepatic esterase antibody inhibited the steroid esterase activity not only in the liver but also in serum; and (3) monensin, which prevents the secretion of various kinds of secretory proteins by disrupting the function of the Golgi apparatus, inhibited the elevation of the steroid esterase activity in serum by dexamethasone but did not affect the induction in liver.

Determination of enzyme activities in serum for the detection of xenobiotic effects on the liver

The determinations of enzyme activities in the serum are of considerable importance in detecting xenobiotic effects on the liver. After a brief introduction to the basics of enzyme diagnostics, the enzymes ALAT, ASAT, ICDH, LDH, SDH, GLDH, AP, gamma-GT, CHE are characterized with regard to their occurrence, their half-life periods in the serum and their clinical value. They are followed by enzyme levels and the presentation of the dynamics of enzyme activities in the serum after xenobiotic influences on the liver in humans.

Diagnostic application of mitochondrial enzymes and isoenzymes

Evolutionary, topological and metabolic aspects of mitochondrial enzymes and isoenzymes are reviewed, and the structural and functional heterogeneity of mitochondria is demonstrated. Primary deficiencies of mitochondrial enzymes are described and the need for their proper recognition is illustrated. Species differences of secondary dysfunction of mitochondrial enzymes are shown. The release of mitochondrial enzymes is compared to that of cytosolic enzymes from liver and heart muscle cells and the diagnostic significance of assays of mitochondrial enzymes in serum is evidenced. Possible mechanisms of mitochondrial enzyme release from cells and unresolved questions pertaining to this process are discussed in light of potential diagnostic utility of mitochondrial enzymes in serum.

Evaluating toxin-induced hepatic injury in rats by laboratory results and discriminant analysis

The ability of 14 serum biochemical assays to predict the presence of hepatic necrosis induced by carbon tetrachloride (CCl4) (centrilobular necrosis), allyl alcohol (periportal necrosis), and 1-napththylisothiocyanate (ANIT) (biliary duct necrosis) was evaluated in rats. Results of these assays were analyzed using multivariate discriminant analysis to determine: which assays have the highest predictive value for discriminating between control and treated rats, and which assays would discriminate between rats in the three treatment groups. Individual assays with the highest predictive value for CCl4-induced lesions versus controls were glutamate dehydrogenase (GDH), sorbitol dehydrogenase (SDH), and alanine aminotransferase (ALT). Assays with the highest predictive value for ANIT-induced lesions were GDH, 5'-nucleotidase (5'NT), and ALT. Assays the highest predictive value for ANIT-induced lesions were GDH, 5'-nucleotidase (5'NT), and ALT. Assays with the highest predictive value for allyl alcohol-induced lesions were an ALT/isocitrate dehydrogenase (ICD) ratio, GDH, and ALT. Canonical correlation coefficients for each assay ranged from 0.98 to 0.91 with 95-100% correct group membership predictions (treated versus control) provided by each assay. Individual assays were not highly predictive for determining group membership among all three treatment groups. A two assay combination of 5'NT and an ALT/ICD ratio provided 100% correct group membership predictions and had high canonical correlations (f1 = 0.95, f2 = 0.83).

Response of isolated hepatocytes to organic and inorganic cytotoxins

Thirty-four chemicals-diverse in structure, postulated mechanisms of action, and primary target organs--were tested for cytotoxic response in isolated hepatocyte suspensions from young male Sprague-Dawley rats. Hepatocytes were incubated in the presence and absence of the test chemicals in closed vessels fitted with side arms for serial sampling for up to 5 h at 37 degrees C with gentle shaking under an O2:CO2 (95:5) atmosphere. The parameters evaluated were glutamate-oxaloacetate transaminase and lactate dehydrogenase release from the cells, Trypan blue exclusion, cell count, urea synthesis capability, and steady-state ATP levels. All chemicals cytotoxic in animals following single or short-term repeated exposures caused statistically significant changes in one or more of these parameters in the 0.01-10-mM concentration range. Dimethylnitrosamine and thioacetamide were not as potent in the isolated cell system as expected from their in vivo hepatotoxicity, and the quantitative changes produced with thioacetamide in the hepatocytes were marginal, even at 10 mM. The solvents tested--ethanol, acetone, dimethyl sulfoxide (DMSO), and propylene glycol--were without effect. These results indicate that isolated hepatocyte suspensions are useful for the identification of cytotoxins in general and hepatotoxins in particular, but that their capability for yielding a quantitative index of cytotoxic potential for diverse chemical species remains to be demonstrated.

Quantitation of cutaneous toxicity: an in vitro approach using skin organ culture

A short-term (48 hr) organ culture system for maintaining metabolically viable and structurally intact mouse skin has been developed. With the culture system, the responses of skin to in vitro physical and chemical insults were assessed by histologic examination and selected biochemical measurements in an attempt to establish a quantitative basis for the evaluation of cutaneous toxicity in vitro. In studies with mouse skin in organ culture following either freeze-thaw treatment (physical insult) or a single in vitro topical application of tributyltin chloride (10 to 1000 nmole/cm2), deleterious morphologic changes were observed. The degree of cellular injury was reflected by inhibition of in vitro incorporation of [3H]thymidine and [14C]leucine into epidermal DNA and protein, respectively; there also was leakage of intracellular enzymes into the culture medium in a dose and time related manner. These biochemical parameters are sensitive indicators of cellular injury; as such they may offer a simple, sensitive, and quantitative measure for assessing cutaneous toxicity of chemicals in vitro.

Circulating lysosomal enzymes and acute hepatic necrosis

The activities of the lysosomal enzymes acid and neutral protease, N-acetylglucosaminidase, and acid phosphatase were measured in the serum of patients with fulminant hepatic failure. Acid protease (cathepsin D) activity was increased about tenfold in patients who died and nearly fourfold in those who survived fulminant hepatic failure after paracetamol overdose, whereas activities were increased equally in patients with fulminant hepatic failure due to viral hepatitis whether or not they survived. A correlation was found between serum acid protease activity and prothrombin time, and the increase in cathepsin D activity was sustained over several days compared with aspartate aminotransferase, which showed a sharp early peak and then a fall. Circulating lysosomal proteases can damage other organs, and measurement of their activity may therefore be of added value in assessing prognosis in this condition.