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Xanthurenic acid (XA), a lateral reaction product of tryptophan metabolism in the omochrome pathway of eye pigment synthesis in insects, induces gametogenesis of malaria parasites. We have succeeded in measuring XA contents in the mosquito tissues using a high performance liquid chromatography with electrochemical detection system. XA content is not enough for activating gametocytes in the midgut where blood meal is taken. We have found that the salivary gland of mosquito contains a sufficient amount of XA for activating gametocytes and mosquito ingests saliva into the midgut during blood feeding. Taken together, it is likely that XA is discharged from salivary gland during blood feeding and is swallowed to the midgut where it affects malaria gametocytes. In the present study, we compared young mosquitoes (2–3 day-old after emergence) with old mosquitoes (12–14 day-old after emergence) in terms of transmission efficacy. XA contents in whole body and the salivary gland were larger in the young group. Numbers of oocyst developed on the midgut after taking blood from the same mouse with malaria were also higher in the young group. When both groups fed a blood meal with cultured ookinetes of malaria parasites, the numbers of oocyst were similar in both groups, suggesting that conditions for development from ookinetes to oocysts were similar in young and old mosquitoes. Taking these results together, we conclude that transmission efficacy is controlled by the amount of XA in the salivary gland.

HIV disease is complicated by the development of a subcortical dementing illness known as AIDS dementia complex (ADC). Highly active antiretroviral therapy (HAART) has effectively lengthened HIV infected patients' life expectancy; indeed some are approaching an age where the risk of Alzheimer's disease (AD) is starting to become significant. Furthermore, many such patients have hyperlipidemia, which increases the risk of AD. Consequently, it is hypothesized that HIV infected patients are at an increased risk of AD or an illness that is very much like it. While this is a subcortical dementia and as such is quite different from AD, there are similarities especially in regard to the important role of neuroinflammation. Activation of the tryptophan metabolism via the kynurenine pathway (KP) and more particularly production of one of its end-products, excitotoxin quinolinic acid (QUIN), may play a central role in the amplification of the inflammatory mechanisms, amyloid plaque formation and even increase the rate of viral infection of brain cells.

The hepatic kynurenine pathway of tryptophan (Trp) degradation produces a number of physiologically active intermediates. Using our recently developed HPLC procedure for separation and quantification of Trp and 6 of its kynurenine metabolites (kynurenine, 3-hydroxykynurenine, 3-hydroxyanthranilic, kynurenic, xanthurenic and anthranilic acids), we investigated Trp disposition along this pathway in normal human subjects under basal conditions and after acute Trp loading. From 114 fasting US subjects, we have established means and normal ranges for Trp and the above 6 kynurenines. A small (− 13%) gender difference was observed only in Trp in females. Ethnic differences were noted in fasting baseline plasmas, especially in 3-hydroxyanthranilic acid (3HAA), which was much lower in African Americans (n = 50) and Asians (n = 6), than in Hispanics (n = 18) or Caucasians (n = 40). Even after a 5.15–10.30 g Trp load, there was very little rise in 3HAA in African Americans or Asians, compared with Caucasians and Hispanics. We suggest that African Americans and possibly also Asians have a lower kynureninase activity, which has possible implications for health and disease. We propose a new index of Trp oxidation via the kynurenine pathway, the percentage total kynurenines/Trp ratio, which is more representative than the corresponding kynurenine/Trp index. Our results present a unique insight into human kynurenine pathway metabolism and suggest that further studies may help understand and/or elucidate biochemical mechanisms in health and disease.

The state of the art of recent analytical method developments, applied on the one part on the reliable and reproducible quantitation of tryptophan in protein hydrolyzates, on the other part proper for the identification and quantification of tryptophan and its metabolites in biological matrices originating both from the indolyl- and kynurenine pathways. Analytical processes are evaluated and criticized on the basis of their advantages and shortcomings (selectivity, sensitivity, time/cost requirement, etc).

We analyzed products of tryptophan residues in two model proteins which were reacted with reactive nitrogen species. We modified human Cu, Zn-superoxide dismutase, which has a single tryptophan residue and no tyrosine residue, by using two reactive nitrogen species generating systems; peroxynitrite/CO₂ and myeroperoxidase/H₂O₂/NO₂⁻ systems. We identified 6-nitrotryptophan as a major nitration product along with other oxidized products as the reaction products of tryptophan residue by using LC-MS/MS and HPLC-photodiode array analyses of the tryptic peptides. We modified hen egg-white lysozyme as a model of a simple protein having both tryptophan and tyrosine residues by peroxynitrite/CO₂ system. The modified enzyme lost 89% of the enzymatic activity. Among six tryptophan residues in lysozyme, Trp62, Trp63, and Trp123 were nitrated to form 6-nitrotryptophan, along with the formation of 3-nitrotyrosine in all tyrosine residues. However, the efficiency of nitration was different for each residue. No oxidized product of tryptophan residue was observed in the modified lysozyme. In conclusion, we propose that 6-nitrotryptophan is a unique and major nitrated product of tryptophan residue in proteins reacted with reactive nitrogen species.

Dietary polyunsaturated fatty acid (PUFA) suppresses hepatic α-Amino-β-carboxymuconate-ε-semialdehyde decarboxylase (ACMSD) [EC4.1.1.45] activity and mRNA level in rats. In this study, to examine whether down-regulation of ACMSD mRNA by PUFA involves PPARα-mediated mechanism or not, we investigated the effect of PUFA on the ACMSD level by using primary cultured rat hepatocytes. The primary cultured hepatocytes which were isolated from rats were incubated with fatty acids, WY-14,643 (a PPARα agonist) and/or MK-886 (a PPARα antagonist). ACMSD and acyl-CoA oxidase (ACO) as peroxisome marker enzyme mRNA level levels were determined by competitive RT-PCR method. These results lead us to the conclusion that the mechanism of decreased level of ACMSD mRNA by PUFA was different from that by WY-14,643, suggesting that there would be pathways other than a PPARα-mediated one for PUFA to regulate ACMSD mRNA level.

Purpose: Although ovarian cancer is considered highly responsive to combination therapy with paclitaxel (PTX) and carboplatin (CBDCA), cancer recurs rapidly in more than 50% of responsive patients, and in many cases, the recurring cancer cells develop chemoresistance. Therefore, countering chemoresistance is essential for ovarian cancer management. We aimed to find key molecules associated with chemoresistance using gene expression profiling as a screening tool. Experimental Design: Using 2 newly established PTX-resistant ovarian cancer cell lines from an original PTX-sensitive cell line and 4 super-sensitive and 4 refractory surgical ovarian cancer specimens from PTX-based chemotherapy, molecules associated with chemoresistance were screened with gene expression profiling arrays containing 39,000 genes. We further analyzed 44 genes that showed significantly different expressions between PTX-sensitive samples and PTX-resistant samples with permutation tests, which were common in cell lines and patients' tumors. Results: Eight of these genes showed reproducible results with the real time reverse transcriptase polymerase chain reaction, of which indoleamine 2, 3-dioxygenase (IDO) gene expression was the most prominent and consistent. Moreover, by immunohistochemical analysis using a total of 24 serous type ovarian cancer surgical specimens (stage III: n = 21, stage IV: n = 7), excluding samples used for GeneChip analysis, the Kaplan–Meier survival curve showed a clear relationship between IDO staining patterns and overall survival (log-rank test: p = 0.0001). All patients classified as negative survived without relapse. The 50% survival of patients classified as sporadic, focal and diffuse was 41, 17 and 11 months, respectively. Conclusion: The IDO screened with the GeneChip was positively associated with PTX resistance and with impaired survival in patients with serous type ovarian cancer.

Hepatic α-amino-β-carboxymuconate-ε-semialdehyde decarboxylase (ACMSD) plays a key role in regulating NAD biosynthesis. In normal rats, ACMSD has been generally detectable only in the liver and kidneys. Therefore, there is a possibility that liver or kidney injury affects tryptophan–niacin metabolism. We previously reported the significant change of tryptophan–niacin metabolism in rats with liver cirrhosis or in rats with d-galactosamine injected liver injury. In this experiment, we investigated the change of tryptophan–niacin metabolism in rats treated with puromycin aminonucleoside (PAN)-induced nephrosis, the mechanisms responsible for their change of urinary excretion of nicotinamide and its metabolites, and the role of the kidney in tryptophan–niacin conversion. In PAN-treated rats, the sum of urinary excretion of nicotinamide and its metabolites was significantly lower compared with controls. Although kidney ACMSD activity was reduced, the conversion of tryptophan to niacin tended to be lower in the PAN-treated rats. The reduction of urinary excretion of niacin in nephrotic rats may be due to the reduction of blood tryptophan concentration. The role of the kidney ACMSD may be insignificant concerning tryptophan–niacin conversion under this experimental condition.

It is well established that the brainstem contains discrete groups of serotonin-containing neurons with extensive axonal processes that distribute throughout the neuroaxis. Serotonergic neurons have been implicated in a range of functions including sleep/wakefulness, feeding, affect/emotion, thermoregulation, and cognitive behaviors. We describe the projections and some functional properties of the two major serotonergic cell groups of the brain, the dorsal raphe (DR) and the median raphe (MR) nuclei. DR fibers distribute widely throughout the forebrain to dopamine-containing nuclei of the ventral midbrain, the lateral hypothalamus, the midline thalamus, amygdala, the dorsal and ventral striatum and adjoining regions of the basal forebrain, and most of the cortex. By contrast with DR, MR is a midline/paramidline system of projections. Specifically, MR fibers mainly distribute to forebrain structures lying on or close to the midline including the medial mammillary and supramammillary nuclei, posterior and perifornical nuclei of the hypothalamus, midline and intralaminar nuclei of the thalamus, lateral habenula, medial zona incerta, diagonal band nuclei, septum and hippocampus. Overall, MR projections to the cortex are light. With few exceptions, DR and MR project to separate, non-overlapping regions of the forebrain — or, in effect, DR and MR share the serotonergic innervation of the forebrain. We discuss roles for DR in sleep/wake control, feeding/appetite and mood/affect, and for MR in the control of electroencephalographic (EEG) activity of the hippocampus — or states of hippocampal EEG desynchronization.