The inhibitory effect of thioproline on carcinogenesis induced by N-benzylmethylamine and nitrite

Investigation of anti-proliferative and anti-angiogenic properties of Parkia javanica bark and fruit extracts in zebrafish

The use of herbal products as traditional medicines has been a practice in India for centuries. Due to high ethnic diversity, the pool of herbal medicines is enormous, and they are often preferred over modern medicines in certain parts of the country. Cancer is one of the major non-communicable diseases affecting people worldwide. Despite considerable research, cancer is a disease that is still not understood completely, and there have been constant efforts towards the identification of novel drugs or approaches in cancer management. Parkia javanica, an important medicinal plant and a rich source of flavonoids and terpenoids, is widely studied for its antioxidant and anti-inflammatory activities. Traditionally, the fruit and bark extracts of P. javanica find use as home remedy for dysentery and piles in NE India. Moreover, the fruits are consumed by the people of North-East (NE) India as vegetables, either in steamed or cooked form. In this study, crude extracts of P. javanica fruit and bark were obtained, the sub-lethal dose was determined and were then analyzed for anti-proliferative and anti-angiogenic properties using a battery of assays in zebrafish embryos. The sub-lethal concentration 50 (LC50) was found to be 28.66 mg/L and 346.66 mg/L for bark and fruit extract respectively, indicating a decreased toxicity of the fruit extract compared to that of the bark. The anti-proliferative and anti-angiogenic properties were more pronounced for the fruit extract compared to the bark extract. Although preliminary, the results of the study suggest that P. javanica fruits possess potent anti-angiogenic and anti-proliferative properties, which can be further studied for the isolation of active phytochemicals for use as therapeutic agents.

Hot spring bathing accelerates wound healing and enhances heat retention effect in guinea pigs

This study aimed to demonstrate the effects of hot springs on wound healing and heat retention by performing comparative experiments with tap water. The hot spring water used in this study was from an alkaline hot spring that was rich in sodium and chloride ions and exhibited high reducibility. Guinea pigs were divided into a hot spring bathing group and a tap water bathing group, and a bathing test was conducted for eight consecutive days. A comparison of the plasma amino acid composition between the two groups after the bathing test revealed differences in the concentrations of several amino acids associated with wound healing. Image analysis demonstrated that wounds made on the abdominal skin of guinea pigs were significantly contracted by hot spring bathing compared to that by tap water bathing, and histopathological findings showed that wound healing was accelerated. In the thermography test, changes in body surface temperature after bathing were investigated in both groups. The heat retention effect was not observed in the tap water bathing group after bathing, whereas it was enhanced in the hot spring bathing group until 30 min after bathing. In conclusion, this study demonstrated that hot spring bathing accelerates wound healing and has a more significant heat retention effect than tap water bathing.

Evidence for Proline Catabolic Enzymes in the Metabolism of Thiazolidine Carboxylates

Thiazolidine carboxylates such as thiazolidine-4-carboxylate (T4C) and thiazolidine-2-carboxylate (T2C) are naturally occurring sulfur analogues of proline. These compounds have been observed to have both beneficial and toxic effects in cells. Given that proline dehydrogenase has been proposed to be a key enzyme in the oxidative metabolism of thioprolines, we characterized T4C and T2C as substrates of proline catabolic enzymes using proline utilization A (PutA), which is a bifunctional enzyme with proline dehydrogenase (PRODH) and l-glutamate-γ-semialdehyde dehydrogenase (GSALDH) activities. PutA is shown here to catalyze the FAD-dependent PRODH oxidation of both T4C and T2C with catalytic efficiencies significantly higher than with proline. Stopped-flow experiments also demonstrate that l-T4C and l-T2C reduce PutA-bound FAD at rates faster than proline. Unlike proline, however, oxidation of T4C and T2C does not generate a substrate for NAD⁺-dependent GSALDH. Instead, PutA/PRODH oxidation of T4C leads to cysteine formation, whereas oxidation of T2C generates an apparently stable Δ⁴-thiazoline-2-carboxylate species. Our results provide new insights into the metabolism of T2C and T4C.

Quantitation of Thioprolines in Grape Wine by Isotope Dilution-Liquid Chromatography-Tandem Mass Spectrometry

Cysteine reacts with reactive carbonyls to form thioprolines, which have been demonstrated to possess various pharmaceutical properties. Therefore, thioproline formation is considered as a major detoxification pathway for carcinogenic reactive carbonyls. In this study, we report the initial identification of thiazolidine-4-carboxylic acid (1) and 2-methylthiazolidine-4-carboxylic acid (2), two very common thioprolines, formed by reacting formaldehyde and acetaldehyde with cysteine in grape wine samples. We have developed an isotope dilution-liquid chromatography-tandem mass spectrometry method featuring high sensitivity (limit of detection of ≤1.5 ng/mL) and selectivity to quantitate compounds 1 and 2. The method after validated to be highly accurate (recovery of ≥92%) and precise [intraday relative standard deviation (RSD) of ≤4.1% and interday RSD of ≤9.7%] was applied to determine the varying compound 1 and 2 contents in grape wine samples. Results revealed the grape type and storage duration-dependent formation of thioprolines in grape wines. Overall, the results are expected to facilitate compound-dependent investigations of the health benefits of grape wine, and our findings could be adopted to predict the age of grape wine.

Determination of thiazolidine-4-carboxylates in urine by chloroformate derivatization and gas chromatography-electron impact mass spectrometry

The derivatization method of thiazolidine-4-carboxylic acid (TZCA) and methyl-thiazolidine-4-carboxylic acid (Me-TZCA) in urine with alcohol/chloroformate was achieved. TZCA and Me-TZCA were derivatized in one step in urine with ethyl chloroformate in 1 min at room temperature. The derivatives of TZCA and Me-TZCA had very good chromatographic properties and offered very sensitive response for gas chromatography-electron impact ionization-mass spectrometry (GC-EI-MS). On the basis of derivatization, the method for simultaneous determination of TZCA and Me-TZCA in human urine was developed. Deuterated Me-TZCA (Me-TZCA-d(4)) was synthesized as the internal standard (IS) for the analysis of urine samples. TZCA and Me-TZCA were derivatized and extracted from urine at pH 9.5 with toluene, and then the dried extract was dissolved with 100 microl ethyl acetate and injected in GC/MS system. The recoveries of TZCA and Me-TZCA were about 102 and 103%, respectively, at the concentration of 0.05 mg/l. The method detection limits (MDL) were 1.0 and 0.5 microg/l, respectively, for TZCA and Me-TZCA in 1 ml human urine. The coefficients of variation of TZCA and Me-TZCA were less than 6% at the concentrations of 0.05 and 0.2 mg/l, respectively. To assess the formation of TZCA during inhalation with formaldehyde (FA) (about 3.1 and 38.1 ppm FA in air), urine samples from rats were taken during 3 days after initiation of treatment. The mean amount of TZCA determined was 0.07 mg/l in control group and 0.18 mg/l during treatment with 3.1 ppm. The TZCA levels increased up to about 1.01 mg/l during treatment with 38.1 ppm. It is planned to study whether urinary TZCA can be used as an indicator in the biological monitoring of exposure to FA.

Dietary thioproline decreases spontaneous food intake and increases survival and neurological function in mice

Male mice on a diet supplemented with thioproline (l-thiazolidine-4-carboxylic acid), a physiological metabolite of 5-hydroxytryptamine, at 2.0 g/kg of food from 28 weeks of age and for their entire life, showed a 23-29% increased median and maximal life span. These survival increases were associated with improved neurological functions. Compared to control mice, thioproline-supplemented mice had a 20% lower integral spontaneous food intake, and 10% lower body weight at 100 weeks of age. Body weight showed a statistically significant inverse relationship with survival and neurological performances. Thioproline-supplemented mice exhibited a 58-70% decrease of the age-dependent oxidative damage in brain and liver mitochondria at 52 weeks (old mice) and 78 weeks (senescent mice) of age, respectively. The age-associated decrease of brain mitochondrial enzyme activities, NADH-dehydrogenase, cytochrome c oxidase, and mitochondrial nitric oxide synthase (mtNOS), in old and senescent mice were markedly prevented (51-74%) by thioproline. In vitro, thioproline neither exhibited direct antioxidant activity nor had any effect on the electron transfer or mtNOS functional activities of brain and liver mitochondria. It is surmised that thioproline induces an anorexic effect associated with improved survival and neurological function through a decreased oxidative damage and regulation that may involve hypothalamic appetite centers.

Cancer prevention: past, present, future

There are many examples of different types of cancers that have been prevented by appropriate measures in the past. Most of them were related to occupational, iatrogenic or accidental factors, often as the outcome of heavy exposure of humans to specific carcinogenic agents. Cancer is a disease of DNA, and is generally associated with multiple genetic alterations, these being produced in the typical case by exposure to various carcinogens, each of which exists at minute concentrations. Thus, the impact of carcinogenic factors, xenobiotics and autobiotics, is due to their actions in concert. However, a single mutation yielding genomic instability exerts a disproportionately large influence by resulting in a large number of secondary mutational events. Epigenetic changes can also not be disregarded especially from the view point of prevention of neoplasia. The occurrence of multiple primary cancers among survivors of initial primaries, and the presence of hereditary groups with a high risk of cancer development provide a strong stimulus for establishment of effective approach for cancer prevention, which should be, in principle, multi-faceted. Therefore, a holistic approach is essential with improvement in life style including choosing a balanced diet and avoidance of cigarette smoking and other sources of carcinogens, as integral elements.

Thiazolidine derivatives as source of free L-cysteine in rat tissue

The present study demonstrates that a variety of thiazolidine-4-(R)-carboxylic acids (TDs) which are the products of reactions of L-cysteine (cys) with carbonyl compounds could serve as a "delivery" system for cys to the cell. Liberation of the amino acid can occur enzymatically as well as non-enzymatically. The two possibilities have been proven by identification of representative compounds. The most specific substrate for mitochondrial enzymatic oxidation was thiazolidine-4-carboxylic acid (CF), the product of the reaction of cys with formaldehyde, and the least metabolized TD was 2-methyl-thiazolidine-4-carboxylic acid (CA), the product of the reaction of cys with acetaldehyde. TDs formed from cys and different sugars were not metabolized at all in mitochondria. N-Formyl-L-cysteine (NFC) the intermediate product of mitochondrial metabolism of CF was ascertained by 1H-NMR spectroscopy whereas N-acetyl-L-cysteine (NAC), the predicted metabolite of CA, was not detected, possibly due to a fast turnover. The further enzymatic hydrolysis of NFC as well as NAC to free cys was demonstrated to take place in the cytoplasm. Non-enzymatic hydrolysis of TDs depended on the chemical nature of the substituents in the thiazolidine (Th) ring. The most stable compound was unsubstituted Th and the least stable were CGlu(D) and CA. Following non-enzymatic ring opening and hydrolysis, CA was converted to methyl-djenkolic acid, which equilibrates with CA. We have identified this new compound by 1H-NMR spectroscopy. TDs may cause both a decrease and an increase in the levels of SH-groups in mitochondria. In the case of the stable CF, which is metabolized only enzymatically, an increase in the levels of SH-groups in mitochondria was observed. This suggests that enzymatic control of the breakdown of TDs prevents overflowing of the cell with thiol groups. The latter seems to be induced by high concentrations of those TDs which are hydrolysed non-enzymatically. This process leads finally to a decrease in free SH-groups by different mechanisms. The findings demonstrate two different mechanisms by which TDs can provide cys to the cells. The biological and pharmacological consequences are discussed.

Mutagenic activity of peptides and the artificial sweetener aspartame after nitrosation

Naturally occurring dipeptides, cholecystokinine (CCK, a tetrapeptide hormone) and the artificial sweetener aspartame were nitrosated for 10-30 min with 40 mM-nitrite (pH 3.5, 37 degrees C), and the resultant products examined for mutagenicity in Salmonella typhimurium TA100. Specific mutagenicities (net revertants per mumol precursor) spanned four orders of magnitude, with CCK being the most potent precursor (4700 revertants/mumol) followed by tryptophyl-tryptophan (Trp-Trp; 1000 revertants/mumol). Aspartame and glycyl-Trp (Gly-Trp) had intermediate activity (300 revertants/mumol), while Gly-Gly and methionyl-methionine were only weakly mutagenic (20 and 12 revertants/mumol, respectively). The dipeptides of aspartic acid, phenylalanine and tyrosine had no detectable mutagenicity (limits of detection 0.5, 40 and 5 revertants/mumol, respectively). Kinetic studies with aspartame and Gly-Trp suggested that the mutagenic products arose primarily from nitrosation of the primary amine rather than the amide or indole group. The mutagenicities of nitrosated aspartame and Gly-Trp were higher in TA100 than in TA98, and higher without than with enzymatic activation (S-9 mix) in both strains. The time-course study of Trp-Trp nitrosation showed the production of at least two mutagens: a potent but unstable mutagenicity was seen at very short nitrosation times and a more stable but weaker effect was obtained after more than 60 min of nitrosation. Not only the absolute specific mutagenicity but also the nitrite dependence of the nitrosation reaction and the stability of the nitroso product must be taken into account in determining the risk posed by endogenous nitrosation of foods in the human stomach. Under stomach conditions, nitrosation of the side-chains of certain Trp peptides would be expected to contribute more to the endogenous burden of nitrosated products than nitrosation of aspartame or Gly peptides.

Inhibition of mutagenesis by p-aminobenzoic acid as a nitrite scavenger

Nitrite treatment enhances the direct-acting mutagenicity of various foodstuffs (e.g., chicken, bloater, the soybean flour 'kinako', and Ban-Ban-Chi sauce) on Salmonella typhimurium TA100. p-Aminobenzoic acid (PABA) and glutathione (GSH) reduced this mutagenicity; on the other hand, thioproline (TPRO) increased it. PABA seemed more effective than TPRO in scavenging nitrite ion. In analysis of the reactions of PABA and sodium nitrite under acidic conditions (pH 3.0), p-hydroxybenzoic acid (PHBA) was identified as a major reaction product. The reaction seems to involve two steps, diazotization and diazonium substitution. PHBA was not mutagenic to four strains (TA97, TA98, TA100 and TA102) of S. typhimurium with or without S9 mix.

Detoxifying potential of thioproline against N-nitroso compounds, N-nitrosodimethylamine and N-nitrosocimetidine

Thioproline (TPRO), an effective nitrite trapping agent in vivo, was examined for its detoxifying ability in rats against N-nitrosodimethylamine (NDMA) and N-nitrosocimetidine (NCIM). When NDMA (37-101.5 mg/kg) was administered with TPRO (532 mg/kg), no influence of TPRO on NDMA-induced lethality and histological results in liver were observed. NDMA oxygenase activity measured by formaldehyde formation was not affected either. Denitrosation is a route of detoxication of N-nitroso compounds. When NCIM (100 mg/kg), a direct acting mutagen but not carcinogen, was given by gavage with TPRO, urinary excretion of N-nitrosothioproline (NTPRO) in rats apparently increased compared with TPRO alone. This result shows that TPRO is a trapping agent in vivo for nitrosating (NO) species originating from N-nitroso compounds, e.g., NCIM, which are denitrosated non-enzymatically in stomach acidic conditions. Transnitrosation from NDMA to TPRO, where enzymatic denitrosation is required, did not occur in measurable amount after oral administration of NDMA and TPRO.