Effects of taurine on bleomycin-induced lung fibrosis in hamsters

Four groups of hamsters were assigned as saline + saline, taurine + saline (TS), saline + bleomycin (SB), and taurine + bleomycin (TB). The animals were treated with either saline or taurine (500 mg/kg ip) for 1 week and just prior to intratracheal instillation of bleomycin (7.5 units/kg) or saline on the eighth day. Thereafter, taurine administration was continued ip (250 mg/kg) and in drinking water (1%) for another 14 days. Bleomycin-induced increases in lung collagen were significantly inhibited in TB hamsters. Plasma taurine concentration in the TS group was significantly higher than that of the other groups. Lung lavage (bronchoalveolar lavage fluid) taurine in the SB group was significantly higher than the saline + saline and TS groups. Bronchoalveolar lavage fluid supernatant protein and acid phosphatase levels in the SB and TB groups were significantly increased over the saline + saline and TS groups. Although the total number of cells recovered in bronchoalveolar lavage fluid was not different among the four groups, there were significantly fewer neutrophils in the TB as compared with SB hamsters. Morphometric analysis revealed less than half as much lesion (diffuse mononuclear alveolitis and multifocal fibroplasia) in TB as compared with SB hamsters. Also, consolidated foci were less frequent and smaller in TB as compared with SB hamsters. Taurine may attenuate bleomycin-induced inflammation and fibrosis by scavenging reactive oxygen metabolites.     

Effect of taurine on cholesterol metabolism in hamsters: up-regulation of low density lipoprotein (LDL) receptor by taurine

The effects of taurine on hepatic cholesterol metabolism were investigated in hamsters fed a high-fat diet or normal chow. Two weeks-treatment of taurine at 1% in drinking water prevented high-fat diet-induced increase in cholesterol levels of serum and liver. The decrease in serum cholesterol by taurine was due to decrease in non-HDL cholesterols. A similar tendency was noted in serum and liver cholesterol levels of hamsters fed a normal diet. In hamsters fed a high-fat diet, taurine prevented elevation in hepatic activity of acyl-CoA:cholesterol acyltransferase (ACAT) and increased the activity of cholesterol 7alpha-hydroxylase. Taurine also increased cholesterol 7alpha-hydroxylase activity in hamsters fed normal chow. Studies on liver membranes revealed that taurine increased 125I-labeled LDL binding by 52% and 58% in hamsters fed either a normal chow or high-fat diet, respectively. Furthermore, LDL kinetic analysis showed that taurine intake resulted in significant faster plasma LDL fractional catabolic rates (FCR). These results suggest that taurine elevates hepatic LDL receptor and thereby decreases serum cholesterol levels, an event which may be the result of hepatic cholesterol depletion as a consequence of increased bile acid synthesis via enhancement of cholesterol 7alpha-hydroxylase activity. Thus, up-regulation of the LDL receptor and subsequent increase in receptor- mediated LDL turnover may be a key event in the cholesterol-lowering effects of taurine in hamsters.     

Effect of taurine on the potassium content of rat thymocytes after irradiation

Potassium content of the in vitro irradiated thymocytes and in thymocytes isolated from rats at different time intervals following irradiation was shown to decrease. Taurine added to the incubation medium decreased the postirradiation loss of potassium ions by cells.     

Construction of cosmid genomic libraries for the normal and myopathic Syrian hamsters

Cosmid genomic libraries from both normal and myopathic Syrian hamsters have been constructed. MboI was used to generate 35- to 50-kilobase DNA fragments which were isolated from a 5-25% NaCl gradient. The 35- to 50-kilobase DNA fragments were ligated to the cosmid vector pCV108 and packaged into Escherichia coli DK1. Approximately 3 X 10(5) - 4 X 10(5) clones were obtained per microgram of ligated DNA. Thirteen clones have been isolated from 2 X 10(5) colonies using a cardiac myosin heavy chain clone as a probe. Restriction maps of two of these clones are presented here.     

Effect of fasting, phenobarbital, or hydrocortisone on serum creatine-phosphokinase and aldolase activity in myopathic Syrian hamsters.

The hereditary polymyopathy and cardiomyopathy of inbred Syrian hamsters (UM X 7.1) are associated with a marked elevation of serum creatine phosphokinase (CPK) and aldolase levels. Fasting (overnight) further increases (+100-500%) the serum concentration of these enzymes in myopathic hamsters; however, no such effect is demonstrable in normal hamsters, or in first generation offspring produced by crossbreeding the two strains (myopathic and normal). The changes are reversible, and the enzyme values return to previous levels within 72 hr. Neither phenobarbital nor hydrocortisone prevents the rises, as shown by CPK determinations; on the contrary, hydrocortisone elicits even greater serum enzyme increases.     

Effect of dietary sulfur amino acids on the taurine content of rat tissues

Summary.  The effect of dietary sulfur amino acids on the taurine content of rat blood and tissues was investigated. Three types of diet were prepared for this study: a low-taurine diet (LTD), normal taurine diet (NTD; LTD + 0.5% Met), and high-taurine diet (HTD; LTD + 0.5% Met + 3% taurine). These diets had no differing effect on the growth of the rats. The concentration of taurine in the blood from the HTD- and NTD-fed rats was respectively 1,200% and 200% more than that from LTD-. In such rat tissues as the liver, the taurine content was significantly affected by dietary sulfur amino acids, resulting in a higher content with HTD and lower content with LTD. However, little or no effect on taurine content was apparent in the heart or eye. The activity for taurine uptake by the small intestine was not affected by dietary sulfur amino acids. The expression level of taurine transporter mRNA was altered only in the kidney under these dietary conditions: a higher expression level with LTD and lower expression level with HTD. Received January 8, 2002 Accepted January 18, 2002 Published online August 20, 2002 Authors' address: Dr. Hideo Satsu, Laboratory of Food Chemistry, Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan, Fax: +81-3-5841-8026 E-mail: asatsu@mail.ecc.u-tokyo.ac.jp Abbreviations: HTD, high-taurine diet; NTD, normal taurine diet; LTD, low-taurine diet; TAUT, taurine transporter; CSA, cysteine sulfinate; CDO, cysteine dioxygenase; CSAD, cysteine sulfinate decarboxylase; PBS, phosphate-buffered saline; DIDS, 4,4′-diisothiocyanostilbene-2′,2′-disulfonic acid     

Effect of insulin and taurine on the potassium content of the perfused liver in irradiated rats

Effect of insulin (0.4 units/l) and taurine (0.4 g/l) on potassium transport to a perfusate was studied using perfusing rat liver isolated on the 1st and 3d days following irradiation (18.06.10(-2) C/kg). Both preparations were shown to diminish reliably the release of potassium ions from cellular structures of irradiated rat liver.     

Effects of taurine and verapamil on heart calcium in hamsters and rats

Heart calcium was measured in hamsters and rats following 30 days of drinking (i) tap water, (ii) taurine solution (T) or (iii) a taurine uptake inhibitor (GES). The regimes were duplicated in animals receiving verapamil (V). Heart calcium was reduced in both species by T + V; a comparable effect was obtained with GES alone; T alone had no effect. In the hamster, the GES effect was reversed by GES + V; V alone had no effect. In rats, the separate and combined effects of GES and V on heart calcium were identical. Possible mechanisms and underlying species differences are discussed.     

Effect of cadmium on collagen content and solubility in rat bone

The toxic action of cadmium in the bone tissue is known, but its mechanisms are still unexplained. We examined whether Cd influences collagen content and its solubility in the femoral bone of three-week-old female rats exposed to 5 or 50 mg Cd/l in drinking water. Non-cross linked collagen was extracted with 0.5 M acetic acid, and two acid-insoluble collagen fractions were extracted with pepsin and 4.0 M guanidine hydrochloride, respectively. SDS/PAGE showed the presence of two collagen types, I and V, in all three extracted fractions. Exposure of rats to Cd for 6 months increased the amount of acid-soluble collagens type I and V and decreased the level of acid-insoluble collagens. The amount of total collagen extracted from the bones of rats exposed to 50 mg Cd/l was reduced by about 14% as compared to control and those intoxicated with 5 mg Cd/l. The solubility of type I bone collagen (determined as the percentage of acetic-soluble fraction of total collagen) was increased 2.9- and 3.0-fold in rats intoxicated with 5 and 50 mg Cd/l, respectively. Similarly, the solubility of type V collagen was increased 2.3- and 2.7-fold, respectively. Our results indicate that Cd treatment affects bone collagen by decreasing its content and increasing its solubility.     

Effect of protein and taurine content of maternal diet on the physical development of neonates

The effect of taurine and/or protein composition of maternal diets was examined for effects on survival rates and growth of neonates. Most of the effects observed are attributable to the influence of such diets on both the quantity and quality of the milk supplied to the neonates. The taurine and protein content of the diets exhibit an interdependent relationship with respect to regulating the protein and taurine concentration of the milk. The overall effect of dietary taurine was to increse neonatal survival during the period that the mothers received a protein-defcient diet.     

Comparison of soft tissue calcium levels throughout the life spans of normal and myopathic hamsters

Comparisons of calcium levels in heart, skeletal muscle, brain, liver and plasma were made throughout the life spans of normal and genetically myopathic hamsters. A large calcium accumulation occurred in, and was restricted to, myopathic tissues (heart and skeletal muscle). Calcium elevation in myopathic tissues corresponded to documented lesion appearance, and persisted throughout the remainder of the life span. Calcium buildup in heart and skeletal muscle, as a central feature of the myopathic process, does not reflect a general failure of calcium homeostasis; nonmyopathic tissues are unaffected. Calcium increased moderately in some normal tissues late in life.     

Cloning of the cDNA and nucleotide sequence of a skeletal muscle protease from myopathic hamsters

A neutral protease with an estimated M_r of about 26 kD and responsible for cleavage of myosin LC2 was isolated from hamster skeletal muscle. Complementary DNAs were generated by RT-PCR using total hamster muscle RNA and degenerate oligonucleotide primers based on the sequences of two internal peptides. The nucleotide sequences of the resultant cDNAs were subsequently determined and the complete amino acid sequence of the protease deduced. Although the hamster protein shared 63-85% identity in nucleotide and amino acid sequences with rat and mouse mast cell proteases, it had a higher degree of specificity for myosin LC2 than mast cell proteases which also digested myosin LC1 and myosin heavy chains. As a result, the hamster protease was designated mekratin because of its unique enzymatic specificities to distinguish it from other mast cell proteases. A polyclonal antibody was raised specific to the hamster muscle and human cardiac muscle mekratins without apparent cross-reaction with rat mast cell proteases. We have earlier demonstrated the presence in excess of a neutral protease that specifically cleaves LC2 in human hearts obtained at end stage idiopathic dilated cardiomyopathy (IDC). Western analyses revealed that heart tissue from patients with IDC contained 5-10 fold more mekratin than control samples. Furthermore, the level of the protease in human IDC tissues was similar to that seen in myopathic hamster skeletal muscle. No bands were recognized by the antibody when IDC myofibrils were probed due to the removal of soluble proteins during sample preparation. Thus, these results strongly suggest that the anti-mekratin antibody will provide positive identification of IDC in many cases and diagnosis by exclusion may be replaced.     

Reactivation of autophagy by spermidine ameliorates the myopathic defects of collagen VI-null mice

Autophagy is a self-degradative process responsible for the clearance of damaged or unnecessary cellular components. We have previously found that persistence of dysfunctional organelles due to autophagy failure is a key event in the pathogenesis of COL6/collagen VI-related myopathies, and have demonstrated that reactivation of a proper autophagic flux rescues the muscle defects of Col6a1-null (col6a1^−/−) mice. Here we show that treatment with spermidine, a naturally occurring nontoxic autophagy inducer, is beneficial for col6a1^−/− mice. Systemic administration of spermidine in col6a1^−/− mice reactivated autophagy in a dose-dependent manner, leading to a concurrent amelioration of the histological and ultrastructural muscle defects. The beneficial effects of spermidine, together with its being easy to administer and the lack of overt side effects, open the field for the design of novel nutraceutical strategies for the treatment of muscle diseases characterized by autophagy impairment.     

Effect of ascorbate on collagen synthesis by lung embryonic fibroblasts

Summary Total insoluble collagen and hydroxyproline formation were examined in lung embryonic fibroblasts (IMR-90) grown in the presence or absence of added ascorbate. As expected, when the cells from both groups (+ and −ascorbate) are pulsed with [¹⁴C]proline in the presence of ascorbate, the percent hydroxylation in a 24-hr period does not vary significantly. However, there are dramatic differences in the quantity and quality of the insoluble collagen fraction produced by those cells grown for a long period of time with added ascorbate. Those cells deprived of continuous addition of ascorbate to the culture medium do not display large quantities of accumulated collagen in the cell layer fractions as measured by the hydroxyproline content, whereas the cells grown in the presence of ascorbate contain significant amounts of accumulated collagen. A new method for examining the extracellular insoluble collagen produced in cell cultures is described in these studies. With the aid of pancreatic elastase relatively pure insoluble collagen can be obtained from cells grown in culture. In those cells grown in the presence of ascorbate, the purified insoluble collagen yeilds appropriately banded fibrils when examined in the electron microscope and has an amino-acid composition that is compatible with pure collagen. On the other hand, those cells grown in the absence of ascorbate do not yield purified insoluble collagen as determined by these same criteria. The elastase procedure for the purification of insoluble collagen in cell cultures is simple, easy to use and allows one to assess additional aspects of collagen biosynthesis.     

Effect of dose rate on the induction of experimental lung cancer in hamsters by alpha radiation

The effect of dose rate on the induction of lung cancer in Syrian hamsters by 5.3 MeV alpha particles was examined by varying the number of weekly intratracheal instillations of carrier-free 210Po. By this technique, most of the radiation dose to the lungs was delivered over intervals ranging from 10 to 120 days. Protraction of exposure over 120 days was slightly more carcinogenic at lower total lung doses (24 rad), but slightly less carcinogenic at higher doses (240 rad), than exposure limited to a 10-day interval. No synergism was observed between very low radiation exposures (2.4 rad) and simultaneously administered benzo[a]pyrene. The carcinogenic effect of a single intratracheal instillation of 210Po in isotonic saline was markedly enhanced by subsequent weekly instillations of 0.2 ml of saline alone, emphasizing the importance of noncarcinogenic secondary factors in the expression of radiation-induced lung cancer.     

Physiological and experimental regulation of taurine content in the heart

High concentrations of taurine are found in the heart and these are increased still further in congestive heart failure. It appears that taurine is largely derived by influx from the circulation, and this influx is stimulated by cyclic AMP, whereas influx of alpha-amino acids is unaffected. Influx occurs via a saturable transport system that has strict requirements for ligands. Other substances are transported by this system, including beta-alanine, hypotaurine, guanidoethyl sulfonate, and, to a lesser extent, guanidinopropionate; and these are competitive antagonists for taurine transport. Guanidinoethyl sulfonate, in vivo, markedly lowers taurine concentrations over the course of a few days in all tissues examined in the rat and mouse (but not in the guinea pig). The concentrations of other amino acids are unaffected. Guanidinoethyl sulfonate may prove to be a useful substance in the study of the biological role of taurine, in view of its ability to regulate taurine content in a number of species. Despite the numerous pharmacological actions of taurine, its physiological function in the heart remains problematic. One function appears to be the modulation of calcium movements. The inotropic actions of taurine and beta-adrenergic activation may be linked via the cyclic AMP-dependent regulation of taurine influx.     

Dietary supplementation with taurine and niacin prevents the increase in lung collagen cross-links in the multidose bleomycin hamster model of pulmonary fibrosis

Taurine and niacin have been previously found to block the accumulation of collagen in lung in the multidose bleomycin hamster model of pulmonary fibrosis. Previous studies have found an increase in the pulmonary collagen cross-links dihydroxylysinonoroleucine (DHLNL) and hydroxypyridinium (OHP) in the single dose bleomycin rat model. In this study, we asked if taurine and niacin would block the increase in DHLNL and OHP in the multidose bleomycin hamster model of lung fibrosis. Hamsters were intratracheally instilled with three consecutive doses of saline or bleomycin sulfate 1 week apart (2.5, 2.0,1.5 units/ 5 mL/kg). Animals were fed diet containing either 2.5% niacin and 2.5% taurine or control diet throughout the experiment. The four groups were saline-instilled with control diet (SCD), bleomycin instilled with control diet (BCD), bleomycin-instilled with taurine-niacin in diet (BTN), and saline-instilled with taurine-niacin in diet (STN). Animals were sacrificed at 1, 4, and 8 weeks after the last bleomycin instillation. Hydroxyproline per lung in the BCD group was significantly elevated by 38, 56, and 60% over the SCD group at 1, 4, and 8 weeks, respectively. There were no statistically significant differences among the four groups in DHLNL (mmole) per mole collagen at the 1 or 8 week time point. At four weeks, DHLNL was significantly elevated by 46.4% in the BCD group over the SCD group. The OHP (mmole) per mole of collagen at 1 and 4 weeks in the BCD group was not statistically different from the SCD group. However, at 8 weeks, this was significantly elevated by 31.4% over the SCD group. The DHLNL and OHP contents per mole of collagen were increased in the multidose bleomycin hamster model. Treatment with taurine and niacin in combination prevented the bleomycin-induced increases in the DHLNL and OHP contents of the lung collagen and this may be one of the mechanisms for their antifibrotic effect in this multidose bleomycin hamster model of pulmonary fibrosis.