Plasma protein C activity is enhanced by arsenic but inhibited by fluorescent humic acid associated with blackfoot disease

Blackfoot disease is a peripheral vascular disease causally related to the fluorescent humic acid found in the drinking water of endemic areas in Taiwan. We compared the effects of humic acid (HA) purified from the well water of Blackfoot disease endemic areas with the effects of commercial humic acid (Aldrich) as well as trivalent arsenic (As2O3) on protein C activity, which plays an important role in regulation of blood coagulation and fibrinolysis. Humic acid, either purified from drinking water or obtained commercially, dose-dependently inhibited both activated protein C activity and the activation of protein C induced by Protac, a snake venom-derived protein C activator. In contrast to humic acid, arsenic oxide dose-dependently enhanced both activated protein C activity and the Protac-stimulated activation of protein C. In the presence of humic acid the enhancement effect of arsenic oxide was completely abolished, resulting in concentration-dependent inhibition of protein C activity. Therefore, the results of this study indicate that humic acid is a potent protein C inhibitor even in the presence of arsenic, which enhances the protein C activity. Since protein C is a potent anticoagulant and profibrinolytic agent, acquired defects of protein C induced by humic acid might cause a thrombophilic or hypercoagulable state. Whether this is one of the possible mechanisms of humic acid-induced thrombotic disorders in Blackfoot disease needs to be further characterized.

Humic substances shorten human plasma prothrombin time

The prothrombin time of the normal human pooled plasma was shortened by Aldrich humic acid well water humic substances and lignin at final concentrations ranging from 5 × 10(-3) mg mL(-1) to 5 × 10(-2) mg mL(-1), with a maxmum effect at 1 × 10(-2) mg mL(-1). At this concentration the shortening was 5.5 s, 4.4 s, and 3.5 s by Aldrich humic acid, well water humic substances and lignin respectively. However, monomeric components of humic acid such as syringic acid, protocatechuic acid, pyrogallol, vanillic acid, gallic acid, resorcinol, ferulic acid, catechol, caffeic acid and p-coumaric acid did not have such ability to shorten prothrombin time at the same final concentration ranges. Certain reducing agents such as t-butanol (2.5 × 10(-) -2.0 × 10(-2) mg mL(-1)), glutathione (8.0 × 10(-2)-1 .0 mg mL(-1)), ascorbic acid (4.2 × 10(-2)-5.0 × 10(-1) mg mL(-1)) and dithiothreitol (1.0 × 10(-2)-1.7 × 10(-1)mg mL(-1)) could prevent the shortening effects of humic substances or lignin on prothrombin time. These results suggested that humic substances and lignin with a polymerised structure had an ability to affect activities of some blood coagulating enzymes.

Eugenol triggers different pathobiological effects on human oral mucosal fibroblasts

Pathobiological effects of eugenol (4-allyl-2-methoxyphenol), a major constituent of betel quid (BQ), were studied on oral mucosal fibroblasts. At a concentration higher than 3 mmol/L, eugenol was cytotoxic to oral mucosal fibroblasts in a concentration- and time-dependent manner. Cell death was associated with intracellular depletion of glutathione (GSH). Most of the GSH was depleted prior to the onset of cell death. At concentrations of 3 mmol/L and 4 mmol/L, eugenol depleted about 45% and 77% of GSH after one-hour incubation. In addition, eugenol decreased cellular ATP level in a concentration- and time-dependent manner. Eugenol also inhibited lipid peroxidation. Inhibition of lipid peroxidation was partially explained by its dose-dependent inhibition of xanthine oxidase activity. The IC50 of eugenol on xanthine oxidase activity was about 0.3 mmol/L. No DNA strand break activity for eugenol was found at concentrations between 0.5 and 3 mmol/L. Taken together, frequent exposure of oral mucosa to a high concentration of eugenol during the chewing of BQ might be involved in the pathogenesis of oral submucous fibrosis and oral cancer via its cytotoxicity. In contrast, eugenol at a concentration less than 1 mmol/L might protect cells from the genetic attack of reactive oxygen species via inhibition of xanthine oxidase activity and lipid peroxidation.

Inhibitory effects of phenolics on xanthine oxidase

The stems of Bougainvillea spectabillis Wild (Nyctaginaceae) have been used in folk medicine against hepatitis. Spinasterol, 22, 23-dihydrospinasterol and caffeic acid were isolated from the plant stems and characterized. Caffeic acid has not been previously isolated from this plant but spinasterol has been isolated from the leaves. Caffeic acid was found to be the active principle exhibiting strong inhibition of xanthine oxidase in this study (IC50 = 39.21 microM). In order to study the structure-activity relationship of the phenolics as regards xanthine oxidase inhibition, twelve naturally occurring phenolics (esculetin, scopoletin, scoparone, barbaloin, berberine chloride, sinomenine, osthole, paeonol, honokiol, magnolol, methyleugenol and 6-gingerol) were tested for their inhibitory effects on xanthine oxidase. The results showed that esculetin displayed the strongest activity (IC50 = 28.4 microM), and induced competitive inhibition of the enzyme with respect to the substrate xanthine. The apparent inhibition constant (Ki) of esculetin was 2.369 x 10(-6) M. Since xanthine oxidase serum levels are increased in hepatic and brain tumors, caffeic acid and esculetin should be tested as anti-hepatitis or/and anticancer agents.

Humic acid induces expression of tissue factor by cultured endothelial cells: regulation by cytosolic calcium and protein kinase C

Blackfoot disease is a thrombotic peripheral vascular disease causally related to the fluorescent humic acid (HA) found in the drinking water of wells in endemic areas in Taiwan. In this study we examined the effect of HA on tissue factor (TF) expression by vascular endothelial cells. Incubation of cultured human umbilical vein endothelial cells (HUVEC) with HA isolated from endemic area drinking water or with a synthetic humic acid polymer (SHA), resulted in enhanced cell surface expression of TF activity by HUVEC. The intracellular calcium level ([Ca2+]i) was measured using a calcium-specific fluorescent probe, fura 2. Changes in [Ca2+]i level were followed and quantitatively analyzed by spectrofluorometric microscopy, after incubation of the fura 2-loaded HUVEC with HA or SHA in a medium containing 1.8 mM CaCl2. Both HA and SHA increased [Ca2+]i in the presence of extracellular calcium ions, but not in their absence, indicating that influx of extracellular Ca2+ occurred during incubation of HUVEC with HA or SHA. Verapamil, a potent calcium channel blocker, did not abolish the enhancement of [Ca2+]i induced by HA or SHA, indicating that specific calcium channels may not be involved in the HA/SHA-induced elevation of [Ca2+]i. The elevated [Ca2+]i level induced by HA or SHA returned to basal level following removal of HA or SHA and incubation of the washed cells in medium containing 1.8 mM CaCl2. All these changes occurred in the absence of significant cytotoxic effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Xanthine oxidase inhibitors from the leaves of Alsophila spinulosa (Hook) Tryon

Diploptene(1), beta-sitosterol(2), a mixture of 6'-O-(E-P-coumaroyl)-alpha-glucopyranose and 6'-O-(E-P-coumaroyl)-beta-glucopyranose(3), a mixture of 6'-O-(E-P-caffeoyl)-alpha-glucopyranose and 6'-O-(E-P-caffeoyl)-beta-glucopyranose(4), caffeic acid(5) and astragalin(6) were isolated from an ethanolic extract of the leaves of Alsophila spinulosa Hook Tryon (Cyatheaceae). The plant has been used in folk medicine for hepatitis, gout, rheumatism, and tumor and these compounds were tested for their inhibitory effect on xanthine oxidase. Caffeic acid was the most potent constituent (IC50 = 39.21 microM; Ki = 28.2 microM) and was an uncompetitive inhibitor of the enzyme with respect to the substrate xanthine.

Inhibitory effects of flavonoids on xanthine oxidase

The stems of Bougainvillea spectabillis Wild (Nyctaginaceae) have been used in folk medicine for hepatis, and spinasterol and quercetin were isolated and characterized from the plant leaves in this study. These constituents have not been previously isolated from Bougainvillea spectabillis W. Quercetin, the flavonoid, was found as active principle because it showed a strong activity on xanthine oxidase inhibition (IC50 = 7.23 microM) in this study as well as in the literature. Since xanthine oxidase serum levels are increased in hepatitis and tumoral brain tissues, quercetin may be used for remission of hepatitis or brain tumor. In order to study the structure-activity relationship of the flavonoids as regards xanthine oxidase inhibition, nine naturally occurring flavonoids have been tested the inhibitory effects on xanthine oxidase, such as baicalein, baicalin, capillarisin, d-catechin, d-epicatechin, hesperidin, liquiritin, puerarin and wogonin. The results showed that baicalein displayed the strongest activity (IC50 = 9.44 microM), followed by wogonin (IC50 = 52.46 microM) and then baicalin (IC50 = 71.73 microns). Baicalein induced uncompetitive inhibition of the enzyme with respect to xanhtine and the apparent inhibition constant (Ki) was 2.48 x 10(-6) M.

Stimulation of endothelin production in cultured human endothelial cells by fluorescent compounds associated with blackfoot disease

The fluorescent compounds (FC) in humic substances isolated from the drinking water of endemic areas of blackfoot disease have been characterized as the causative factor of the disease. In this report we studied the effects of these fluorescent compounds on the synthesis and secretion of endothelin-1 by cultured human umbilical cord vein endothelial cells (HUVEC) in order to explore the possible pathological mechanism(s) of FC in the development of atherothrombotic vasculopathy in blackfoot disease. Incubation of confluent HUVEC with FC (100 micrograms/ml) enhanced endothelin mRNA expression. A sensitive ELISA method was developed to quantitate secreted endothelin antigen levels in conditioned medium. Incubation of confluent HUVEC cultures with different concentrations of FC (0-200 micrograms/ml) resulted in concentration-dependent enhanced production of endothelin. No significant changes in endothelin production were observed when subconfluent HUVEC cultures were incubated with FC. FC dose-dependently reduced the growth rate of subconfluent cultured HUVEC and exerted cytotoxic effects on the viability and integrity of confluent HUVEC monolayers. Since endothelin is one of the most potent vasoconstrictors affecting blood pressure and blood flow, and is mitogenic for smooth muscle cell proliferation, these results imply that the enhanced endothelin production and the reduced cell viability and growth rate induced by FC may contribute to the atherothrombotic vasculopathy observed in blackfoot disease.

Arsenic as a promoter in the effect of humic substances on plasma prothrombin time in vitro

Protocatechuic acid can be oxidized and polymerized to from humic substances (humic acid and fulvic acid). Should AS2O3 occur in the process of oxidative polymerization, humic acid output can increase by 1.5 - 2.3 times and, in the case of fulvic acid, at least 10 times. After protocatechuic acid is oxidized and polymerized, the resultant humic and fulvic acids both exhibit the ability to shorten the prothrombin time of human pool plasma in vitro. This ability becomes more apparent when AS2O3 serves as a promoter in the course of oxidative polymerization as described above. However, AS2O3 or protocatechuic acid alone is unable to shorten the prothrombin time of human pool plasma.

Serum immunosuppressive acidic protein levels in blackfoot disease patients and cancer patients

Immunosuppressive acidic protein (IAP) was first found in the ascitic fluids of cancer patients. Its biochemical properties are significantly different from those of acidic protein in the serum of normal persons. Previous studies have indicated that the serum IAP concentration increases in most cancer patients and decreases to a normal level as such patients are cured. Therefore, it has been suggested as a useful marker for follow-up in operated cancer patients. In this study, analyses and comparisons of serum IAP concentrations have been made among 53 normal persons in Blackfoot disease endemic areas, 25 patients with diabetes, cataracts, hypertension and cardiovascular disease in Blackfoot disease endemic areas, 50 breast cancer patients, 13 colorectal cancer patients, and 18 Blackfoot disease patients. Serum IAP concentrations were found as follows: 454 +/- 138 micrograms/ml for normal subjects and 499 +/- 132 micrograms/ml for disease patients in Blackfoot disease endemic areas; 520 +/- 149 micrograms/ml for breast cancer patients; 864 +/- 341 micrograms/ml for colorectal cancer patients and 950 +/- 368 micrograms/ml for Blackfoot disease patients. Serum IAP concentrations were much higher in Blackfoot disease patients, than in normal persons in Blackfoot disease endemic areas (p less than 0.001), and as high as in colorectal cancer patients. In Blackfoot disease patients, the mean serum IAP concentration of 6 patients coming from the Blackfoot disease endemic areas was as high as 1,238 +/- 404 micrograms/ml, showing a positive rate of 100% to IAP (i.e. IAP concentration exceeds 500 micrograms/ml). We conclude that serum IAP assay of Blackfoot disease patients may be useful for prognosis and therapeutic monitoring.

The effect of fluorescent humic substances existing in the well water of Blackfoot disease endemic areas in Taiwan on prothrombin time and activated partial thromboplastin time in vitro

Fluorescent humic substances (FHS) in well water of Blackfoot disease endemic areas were purified and fractionated by Sephadex G-25 column chromatography. Four fractions of the purified FHS were isolated. The purified FHS and their fractions were then added to normal human pool plasma in vitro separately to detect the abilities of the effects on prothrombin time (PT) and activated thromboplastin time (APTT). Results showed that all of the four fractions of the purified FHS prolonged both PT and APTT in the higher concentration ranges (10 mg/ml - 20 mg/ml), but shortened both PT and APTT in the lower concentration ranges (0.5 mg/ml - 5 mg/ml). Among the four fractions of the FHS, the fraction 1, the humic substance with the highest molecular weight among all the four FHS, showed the most obvious effects. Owing to the effects of the FHS on PT and APTT values, we supposed that there is a close relationship between the FHS and the cause of Blackfoot disease.

Serum macro creatine kinase type 2 as a tumor marker in lung cancer: comparison with carcinoembryonic antigen

Macro creatine kinase type 2 (MCK-2), an atypical cathodically migrating creatine kinase isoenzyme, was first detected in the serum of a breast cancer patient in 1978. In recent years, MCK-2 was also found in the sera of several malignancies and has been proposed as a potential tumor marker. Forty two patients with lung cancer. The rates of MCK-2 presence in serum were 56.8%, 29.6%, and 0%, respectively, for primary lung cancer, inflammatory lung disease and normal controls. In primary lung cancer, the rate of presence of MCK-2 was higher than CEA (40.0%), and appeared more frequently in epidermoid cancer (71.3%) and in stages 3 and 4 (65.4%). Serial examinations postoperatively showed that MCK-2 became negative after resection. Carcinoembryonic antigen, MCK-2 or a combination of both was evaluated as a diagnostic aid in 37 patients with a peripheral pulmonary nodule. Sensitivity, specificity and accuracy were 32.0%, 90.9%, 50.0%, 36.4%, 93.3%, 59.5%; 43.8%, 90.5%, 70.3%, respectively, for CEA, MCK-2, and CEA plus MCK-2. It is concluded that MCK-2 is comparable to CEA as a tumor marker in lung cancer. The combination of MCK-2 and CEA is of value as a diagnostic aid in patients with a peripheral pulmonary nodule.

Studies on patients with polychlorinated biphenyl poisoning. 2. Determination of urinary coproporphyrin, uroporphyrin, delta-aminolevulinic acid and porphobilinogen

Urinary excretion of heme precursors were evaluated in 69 human subjects who have consumed rice oil contaminated with polychlorinated biphenyls (PCBs). Twenty four hour urinary samples were collected from 20 normal healthy volunteers and 69 PCB poisoned human subjects and assayed for the concentrations of delta-aminolevulinic acid, prophobilinogen, uroporphyrin and coproporphyrin. PCB poisoning caused an increased excretion of delta-aminolevulinic acid (from 0.72 mg/24 hours to 1.00 mg/24 hours) and uroprophyrin (from 13.6 micrograms/24 hours to 41.2 micrograms/24 hours), but not the excretion of porphobilinogen (0.34 mg/24 hours) or coproporphyrin (30 micrograms/24 hours). The excretion pattern of urinary heme precursors associated with PCB poisoning is different from those due to lead or arsenic poisoning. The analysis of urinary heme precursors may be helpful for screening patients with PCB poisoning.