Quinolinate Phosphoribosyltransferase Research Articles

Dysregulated placental expression of kynurenine pathway enzymes is associated with inflammation and depression in pregnancy

BackgroundPerinatal depression (including antenatal-, postnatal-, and depression that spans both timepoints) is a prevalent disorder with high morbidity that affects both mother and child. Even though the full biological blueprints of perinatal depression remain incomplete, multiple studies indicate that, at least for antenatal depression, the disorder has an inflammatory component likely linked to a dysregulation of the enzymatic kynurenine pathway. The production of neuroactive metabolites in this pathway, including quinolinic acid (QUIN), is upregulated in the placenta due to the multiple immunological roles of the metabolites during pregnancy. Since neuroactive metabolites produced by the pathway also may affect mood by directly affecting glutamate neurotransmission, we sought to investigate whether the placental expression of kynurenine pathway enzymes controlling QUIN production was associated with both peripheral inflammation and depressive symptoms during pregnancy. Methods68 placentas obtained at birth were analyzed using qPCR to determine the expression of kynurenine pathway enzymes. Cytokines and metabolites were quantified in plasma using high-sensitivity electroluminescence and ultra-performance liquid chromatography, respectively. Maternal depressive symptoms were assessed using the Edinburgh Postnatal Depression Scale (EPDS) throughout pregnancy and the post-partum. Associations between these factors were assessed using robust linear regression with ranked enzymes. ResultsLow placental quinolinate phosphoribosyl transferase (QPRT), the enzyme responsible for degrading QUIN, was associated with higher IL-6 and higher QUIN/kynurenic acid ratios at the 3rd trimester. Moreover, women with severe depressive symptoms in the 3rd trimester had significantly lower placental expression of both QPRT and 2-amino-3-carboxymuconate-6-semialdehyde decarboxylase (ACMSD); impaired activity of these two enzymes leads to QUIN accumulation. ConclusionOverall, our data support that a compromised placental environment, featuring low expression of critical kynurenine pathway enzymes is associated with increased levels of plasma cytokines and the dysregulated kynurenine metabolite pattern observed in depressed women during pregnancy.

Abstract 3067: SLC7A5/LAT1 promotes the Warburg Effect for TNBC progression through Trp/QPRT/NAD+ pathway

Abstract SLC7A5/LAT1 is a cross-membrane transporter that functions in uptake of large neutral amino acids into cells. Many pathological studies have shown that LAT1 is highly expressed in cancer tissue from various origins such as lung, biliary tract, breast, prostate, bone, and their metastatic legions. High LAT1 expression has been recognized as a significant prognostic marker in various cancers. Our TCGA data analysis showed that the expression level of LAT1 is higher in TNBC tumors compared with normal breast tissues. The higher expression level of LAT1 is linked with poor overall and progression-free survival. Dysregulation of amino acid transporters lead to metabolic reprogramming, which changes intracellular amino acid levels, contributing to the pathogenesis of cancer. However, it remains elusive whether and how LAT1 re-wires the cellular metabolic programs to promote TNBC tumor proliferation. In this study, we showed that inhibition of SLC7A5/LAT1 significantly reduced TNBC cell proliferation, viability, migration capability while promoting apoptosis. Mechanistically, we found significant positive correlations of LAT1 with PKM2 and LDHA in breast cancer tissues, which are key enzymes in mediating glycolysis and lactate fermentation or the Warburg Effect. Knock down LAT1 via siRNA decreased the expression levels of p-PKM2 and p-LDHA in TNBC cells. Tryptophan, a major substrate amino acid transported into cytosol by LAT1, is the precursor for the de novo synthesis of nicotinamide adenine dinucleotide (NAD+). The enzyme quinolinic acid phosphoribosyltransferase (QPRT) catalyzes the conversion from quinolinate, a product of tryptophan degradation, to NAD+. We showed LAT1 inhibition reduced the expression level of QPRT, cytosolic NAD+/NADH ratio as well as lactate production. Addition of L-Tryptophan increased the levels of p-PKM2 and p-LDHA while knockdown of LAT1 reversed tryptophan-mediated increase of PKM2 and LDHA activities, suggesting that LAT1 may regulate PKM2/LDHA through Trp/QPRT/NAD+ pathway for promoting the Warburg Effect. Additionally, we found upregulations of SLC7A5/LAT1, p-PKM2 and p-LDHA in doxorubicin-resistant cells and PDX mouse model compared with their corresponding controls. Collectively, these results provide evidence that overexpression of LAT1 in TNBC drives cancer progression and drug resistance by reinforcing the Warburg Effect, suggesting LAT1 as a promising therapeutic target for addressing TNBC. Our ongoing work will evaluate whether inhibiting LAT1 genetically or pharmacologically reduces xenograft tumor growth and enhances the sensitivities of TNBC resistant cells to chemotherapy in vivo. Our investigation will elucidate the underlying mechanisms involved in these processes. Citation Format: Margot Y. Fedoroff, Lei Zhao, Leili Saeednejad Zanjani, Jun He. SLC7A5/LAT1 promotes the Warburg Effect for TNBC progression through Trp/QPRT/NAD+ pathway [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3067.

P224 JAK-STAT-Driven Tryptophan Degradation Fuels Mucosal Inflammation through QPRT Suppression-Induced Quinolinic Acid Overflow

Abstract Background Inflammatory bowel disease is characterized by disturbed metabolism, including disrupted tryptophan (TRP) metabolism along the kynurenine pathway (KP). However, the molecular mechanism how this fuels inflammation is not understood. Here, we unravel rewiring of TRP metabolism in IBD by combining murine DSS colitis with multi-omics of longitudinal IBD cohorts. Methods Serum metabolites were associated with CRP, e/pMayo, SESCD and CDAI (n=83 UC, n=51 CD). Mucosal IDO1 and QPRT expression (both KP enzymes; indoleamine2,3-dioxygenase1, quinolinate phosphoribosyltransferase; n=273 UC) was correlated with Nancy index and eMayo. Murine enterocytes were treated with Qprt siRNA, LPS or IFNγ and cytokines measured by RT-qPCR. Tissue and serum of DSS colitis (C57BL/6, 2.5%, 5 days) and human PBMC or colon organoids (hOG) treated with IFNγ or Tofacitinib (Tofa) were analysed by LC-MS. Blood and biopsies for metabolomics and transcriptomics were obtained over 14 weeks from IBD patients (n=62) first introduced to biologics. Mucosal IDO1/QPRT expression was assessed at week 0, 8 and 16 in Tofa-treated UC (n=15). Results In longitudinal IBD therapy intervention cohorts, restoration of serum TRP metabolism was associated with 12-month disease control. Quinolinic acid (QUIN) levels relative to other TRP derivatives positively correlated with several disease activity metrics. Increased mucosal IDO1 and decreased QPRT expression upon proceeding disease severity suggested unbalanced QUIN levels as a joint result of augmented TRP turnover by IDO1 and blocked QUIN conversion by QPRT in active disease. In-vitro, QUIN overflow exaggerated pro-inflammatory cytokine responses. Accumulation of colonic QUIN was reproduced in DSS colitis and resulted in NAD+ (nicotinamide adenine dinucleotide) exhaustion, suggesting a local KP roadblock due to QPRT suppression. Integrated metabolomics and transcriptomics of IBD blood and biopsies confirmed TRP hyper-degradation at the inflammation site and revealed common JAK/STAT pathway upregulation in blood and mucosa. As IDO1 exerts the KP via JAK/STAT, IFNγ-induced KP-activation was rescued by JAK inhibition (JAKi) in human PBMC and hOG. Ultimately, we found mucosal QPRT and IDO1 expression to be significantly associated with therapy response to Tofa in UC, suggesting their baseline expression as an a priori predictor of JAKi therapy response. Conclusion TRP wasting in IBD appears to fuel mucosal inflammation due to QPRT suppression and subsequent QUIN overflow. Whether this mechanism is unique to IBD remains to be shown. Obvious future applications may include diagnostic patient classification and targeting therapeutic interventions in the TRP pathway.

Characteristics of Nutrition and Metabolism in Dogs and Cats.

Domestic dogs and cats have evolved differentially in some aspects of nutrition, metabolism, chemical sensing, and feeding behavior. The dogs have adapted to omnivorous diets containing taurine-abundant meat and starch-rich plant ingredients. By contrast, domestic cats must consume animal-sourced foods for survival, growth, and development. Both dogs and cats synthesize vitamin Cand many amino acids (AAs, such as alanine, asparagine, aspartate, glutamate, glutamine, glycine, proline, and serine), but have a limited ability to form de novo arginine and vitamin D3. Compared with dogs, cats have greater endogenous nitrogen losses and higher dietary requirements for AAs (particularly arginine, taurine, and tyrosine), B-complex vitamins (niacin, thiamin, folate, and biotin), and choline; exhibit greater rates of gluconeogenesis; are less sensitive to AA imbalances and antagonism; are more capable of concentrating urine through renal reabsorption of water; and cannot tolerate high levels of dietary starch due to limited pancreatic α-amylase activity. In addition, dogs can form sufficient taurine from cysteine (formost breeds); arachidonic acid from linoleic acid; eicosapentaenoic acid and docosahexaenoic acid from α-linolenic acid; all-trans-retinol from β-carotene; and niacin from tryptophan. These synthetic pathways, however, are either absent or limited in all cats due to (a)no or low activities of key enzymes (including pyrroline-5-carboxylate synthase, cysteine dioxygenase, ∆6-desaturase, β-carotene dioxygenase, and quinolinate phosphoribosyltransferase)and (b) diversion of intermediates to other metabolic pathways. Dogs can thrive on one large meal daily, select high-fat over low-fat diets, and consume sweet substances. By contrast, cats eat more frequently during light and dark periods, select high-protein over low-protein diets, refuse dry food, enjoy a consistent diet, and cannot taste sweetness. This knowledge guides the feeding and care of dogs and cats, as well as the manufacturing of their foods. As abundant sources of essential nutrients, animal-derived foodstuffs play important roles in optimizing the growth, development, and health of the companion animals.

Jian-Pi-Yi-Shen formula alleviates renal fibrosis by restoring NAD+ biosynthesis in vivo and in vitro.

Patients with chronic kidney disease (CKD) lack efficacious treatment. Jian-Pi-Yi-Shen formula (JPYSF) has demonstrated significant clinical efficacy in treating CKD for decades. However, its renoprotective mechanism has not been fully elucidated. This study aimed to determine whether JPYSF could delay renal fibrosis progression in CKD by restoring nicotinamide adenine dinucleotide (NAD+) biosynthesis. Adenine-diet feeding was used to model CKD in C57BL/6 mice. JPYSF was orally administered for 4 weeks. Human proximal tubular epithelial cells (HK-2) cells were stimulated with transforming growth factor-β1 (TGF-β1) with or without JPYSF treatment. Renal function of mice was assessed by serum creatinine and blood urea nitrogen levels. Renal histopathological changes were assessed using Periodic acid-Schiff and Masson's trichrome staining. Cell viability was assessed using a cell counting kit-8 assay. NAD+ concentrations were detected by a NAD+/NADH assay kit. Western blotting, immunohistochemistry, and immunofluorescence were employed to examine fibrosis-related proteins and key NAD+ biosynthesis enzymes expression in the CKD kidney and TGF-β1-induced HK-2 cells. JPYSF treatment could not only improve renal function and pathological injury but also inhibit renal fibrosis in CKD mice. Additionally, JPYSF reversed fibrotic response in TGF-β1-induced HK-2 cells. Moreover, JPYSF rescued the decreased NAD+ content in CKD mice and TGF-β1-induced HK-2 cells through restoring expression of key enzymes in NAD+ biosynthesis, including quinolinate phosphoribosyltransferase, nicotinamide mononucleotide adenylyltransferase 1, and nicotinamide riboside kinase 1. JPYSF alleviated renal fibrosis in CKD mice and reversed fibrotic response in TGF-β1-induced HK-2 cells, which may be related to the restoration of NAD+ biosynthesis.

Hepatocyte nuclear factor 4α mediated quinolinate phosphoribosylltransferase (QPRT) expression in the kidney facilitates resilience against acute kidney injury

Nicotinamide adenine dinucleotide (NAD+) levels decline in experimental models of acute kidney injury (AKI). Attenuated enzymatic conversion of tryptophan to NAD+ in tubular epithelium may contribute to adverse cellular and physiological outcomes. Mechanisms underlying defense of tryptophan-dependent NAD+ production are incompletely understood. Here we show that regulation of a bottleneck enzyme in this pathway, quinolinate phosphoribosyltransferase (QPRT) may contribute to kidney resilience. Expression of QPRT declined in two unrelated models of AKI. Haploinsufficient mice developed worse outcomes compared to littermate controls whereas novel, conditional gain-of-function mice were protected from injury. Applying these findings, we then identified hepatocyte nuclear factor 4 alpha (HNF4α) as a candidate transcription factor regulating QPRT expression downstream of the mitochondrial biogenesis regulator and NAD+ biosynthesis inducer PPARgamma coactivator-1-alpha (PGC1α). This was verified by chromatin immunoprecipitation. A PGC1α - HNF4α -QPRT axis controlled NAD+ levels across cellular compartments and modulated cellular ATP. These results propose that tryptophan-dependent NAD+ biosynthesis via QPRT and induced by HNF4α may be a critical determinant of kidney resilience to noxious stressors.

Deletion of enzymes for de novo NAD+ biosynthesis accelerated ovarian aging.

Recent advances highlight the pivotal role of nicotinamide adenine dinucleotide (NAD+ ) in ovarian aging. However, the roles of de novo NAD+ biosynthesis on ovarian aging are still unknown. Here, we found that genetic ablation of Ido1 (indoleamine-2,3-dioxygenase 1) or Qprt (Quinolinate phosphoribosyl transferase), two critical genes in de novo NAD+ biosynthesis, resulted in decreased ovarian NAD+ levels in middle-aged mice, leading to subfertility, irregular estrous cycles, reduced ovarian reserve, and accelerated aging. Moreover, we observed impaired oocyte quality, characterized by increased reactive oxygen species and spindle anomalies, which ultimately led to reduced fertilization ability and impaired early embryonic development. A transcriptomic analysis of ovaries in both mutant and wild-type mice revealed alterations in gene expression related to mitochondrial metabolism. Our findings were further supported by the observation of impaired mitochondrial distribution and decreased mitochondrial membrane potential in the oocytes of knockout mice. Supplementation with nicotinamide riboside (NR), an NAD+ booster, in mutant mice increased ovarian reserve and improved oocyte quality. Our study highlights the importance of the NAD+ de novo pathway in middle-aged female fertility.

#3828 KINETICS OF THE DE NOVO NAD/NADH PATHWAY FROM AKI TO CKD

Abstract Background and Aims Mitochondrial dysfunction and energy metabolism deficiency are part of the acute kidney injury (AKI) pathophysiology. In particular, recent studies highlighted the role of nicotinamide adenine dinucleotide (NAD) production in the pathogenesis of AKI. NAD is an electron carrier for mitochondria and a cofactor for cytoplasmic redox reactions. Its production is decreased during AKI following a decreased of the expression of PGC1α (Peroxisome proliferator activated receptor gamma co-activator-1-α). PGC1α inactivation worsened and its overexpression prevented renal injury in a mouse model of renal ischemia. It was also shown that the consequences of PGC1α decreased expression included the alteration of the de novo NAD+ synthesis pathway. This was due to a reduction in the expression of the Quinolinate PhosphoRibosylTransferase (QPRT), which led to an accumulation of quinolinate. Consequently, the quinolinate/tryptophane (uQ/T) ratio increased in the urine. The modulation of this de novo has been studied mainly in the acute phase immediately following the injury. However its evolution with degree of severity and during the transition from AKI to CKD has not been described yet. In order to answer these questions, we designed the following studies: (1) A “severity” study in which we provoked ischemic AKI of increasing intensity in mice and quantified kidney PGC1alpha and QPRT mRNA expression. (2) An “AKI to CKD” study in which we followed kidney PGC1alpha and QPRT mRNA expression and uQ/T. Method Renal ischemia-reperfusion was performed in C57Bl6/J male mice using the new vascular occluder we recently developed (RIRI clamp), after nephrectomy of the contralateral kidney. For the ‘severity’ study, a 5–30 minutes ischemia was performed. Renal function (measurement of plasma creatinine and urea) and structure (Periodic Acid Schiff staining) were assessed 24h after ischemia. For the ‘AKI to CKD’ study, renal ischemia was performed during 10 minutes. Mice were sacrificed 1, 2, 3, 6 and 28 days after ischemia. For both studies, PGC1α and QPRT mRNA expression was quantified by qPCR in the kidneys. Urinary Q/T was determined by mass spectrometry. Results PGC1α and QPRT mRNA expression is inversely corrected to the AKI severity We induced AKI in mice by unilateral ischemia reperfusion injury of increasing time to induce several degrees of AKI severity. The measurement of plasma urea and creatinine concentration confirmed that the severity increased with the duration of ischemia. PGC1α and QPRT mRNA expression decreased progressively with ischemia severity until reaching a plateau at 15 minutes of ischemia for PGC1α (Fig. 1A), like plasma creatinine and urea, whereas QPRT (Fig. 1B) decreased is linear until 30 min of ischemia. PGC1α mRNA decrease is also inversely correlated to kidney dysfunction (p<0.001) (Figue 1C). PGC1α and QPRT expression recovery after AKI A 10-minute ischemia led to the development of Chronic Kidney Disease (CKD), as evidenced by an incomplete recuperation of the kidney function at 28 days. QPRT and PGC1α mRNA expression showed a progressive but incomplete recuperation during the transition from AKI to CKD compared to sham mice (Fig. 1D, E). uQ/T increases after ischemia and is restored during transition from AKI to CKD (Fig. 1F). Conclusion In addition to confirming the decrease of PGCα and QPRT mRNA expression during AKI, we show that it is correlated to the severity of the ischemic AKI. Furthermore, we describe the recovery during renal repair and transition to CKD.

Deletion of quinolinate phosphoribosyltransferase gene accelerates frailty phenotypes and neuromuscular decline with aging in a sex-specific pattern.

Decline in neuromuscular function with aging is known to be a major determinant of disability and all-cause mortality in late life. Despite the importance of the problem, the neurobiology of age-associated muscle weakness is poorly understood. In a previous report, we performed untargeted metabolomics on frail older adults and discovered prominent alteration in the kynurenine pathway, the major route of dietary tryptophan degradation that produces neurotoxic intermediate metabolites. We also showed that neurotoxic kynurenine pathway metabolites are correlated with increased frailty score. For the present study, we sought to further examine the neurobiology of these neurotoxic intermediates by utilizing a mouse model that has a deletion of the quinolinate phosphoribosyltransferase (QPRT) gene, a rate-limiting step of the kynurenine pathway. QPRT-/- mice have elevated neurotoxic quinolinic acid level in the nervous system throughout their lifespan. We found that QPRT-/- mice have accelerated declines in neuromuscular function in an age- and sex-specific manner compared to control strains. In addition, the QPRT-/- mice show premature signs of frailty and body composition changes that are typical for metabolic syndrome. Our findings suggest that the kynurenine pathway may play an important role in frailty and age-associated muscle weakness.

Tryptophan-kynurenine metabolic characterization in the gut and brain of depressive-like rats induced by chronic restraint stress

Accumulating evidence revealed the role of tryptophan (TRP) metabolism, especially its kynurenine pathway (KP), in the communication along the gut-brain axis. However, the underlying characterization of such interaction was not precise. In the present study, the rat depression model was induced by chronic restraint stress (CRS). After depression behavior tests, seven segments (cortex, hippocampus, striatum, hypothalamus, serum, cecum, and colon) along the gut-brain axis were collected to characterize their KP metabolism. mRNA expression of IL-1β, IFN-γ, IL-10 and indoleamine 2,3-dioxygenase 1 (IDO1) enzyme revealed a general inflammatory response and region-specific activated IDO1 along the gut-brain axis. Determination of KP metabolites and enzymes displayed a general KP activation with region-specificity, especially in the hippocampus and colon, where the changes were more pronounced. KYN and 3-HK were increased dramatically along the gut-brain axis; hippocampal KA revealed a significant decrease while colonic KA showed a notable increase, evidenced by the same alternation trends of the corresponding enzymes. The expression of quinolinic acid phosphoribosyltransferase (QPRT), the crucial enzyme to produce NAD+ from QA, was significantly upregulated in the gut but not changed in the brain. Pearson's correlation analysis suggested that kynurenine (KYN), 3-hydroxycaninuric acid (3-HK), serotonin (5-HT), TRP and kynurenic acid (KA) significantly correlated with depressive behaviors in rats. Furthermore, western blot analysis on nod-like receptor protein 3/2 (NLRP3/NLRP2) inflammasome signaling displayed that NLRP3 and cleaved IL-1β/caspase-1 were significantly activated in the hippocampus and colon of CRS rats. However, NLRP2 was only activated in the hippocampus. These results revealed CRS induced inflammatory responses along the brain-gut axis of rats might be controlled through the NLRP3/NLRP2 inflammasome signaling pathway, which may be the underlying regulator for CRS-induced TRP-KYN metabolic changes. This study provides a new experimental background for developing stress-related health products.

Tryptophan metabolism and disposition in cancer biology and immunotherapy.

Tumours utilise tryptophan (Trp) and its metabolites to promote their growth and evade host defences. They recruit Trp through up-regulation of Trp transporters, and up-regulate key enzymes of Trp degradation and down-regulate others. Thus, Trp 2,3-dioxygenase (TDO2), indoleamine 2,3-dioxygenase 1 (IDO1), IDO2, N'-formylkynurenine formamidase (FAMID) and Kyn aminotransferase 1 (KAT1) are all up-regulated in many cancer types, whereas Kyn monooxygenase (KMO), kynureninase (KYNU), 2-amino-3-carboxymuconic acid-6-semialdehyde decarboxylase (ACMSD) and quinolinate phosphoribosyltransferase (QPRT) are up-regulated in a few, but down-regulated in many, cancers. This results in accumulation of the aryl hydrocarbon receptor (AhR) ligand kynurenic acid and in depriving the host of NAD+ by blocking its synthesis from quinolinic acid. The host loses more NAD+ by up-regulation of the NAD+-consuming poly (ADP-ribose) polymerases (PARPs) and the protein acetylaters SIRTs. The nicotinamide arising from PARP and SIRT activation can be recycled in tumours to NAD+ by the up-regulated key enzymes of the salvage pathway. Up-regulation of the Trp transporters SLC1A5 and SLC7A5 is associated mostly with that of TDO2 = FAMID > KAT1 > IDO2 > IDO1. Tumours down-regulate enzymes of serotonin synthesis, thereby removing competition for Trp from the serotonin pathway. Strategies for combating tumoral immune escape could involve inhibition of Trp transport into tumours, inhibition of TDO and IDOs, inhibition of FAMID, inhibition of KAT and KYNU, inhibition of NMPRT and NMNAT, inhibition of the AhR, IL-4I1, PARPs and SIRTs, and by decreasing plasma free Trp availability to tumours by albumin infusion or antilipolytic agents and inhibition of glucocorticoid induction of TDO by glucocorticoid antagonism.

Association of Aging-Related Decline in Quinolinate Phosphoribosyl Transferase Expression and Expression of Profibrotic Genes

Association of Aging-Related Decline in Quinolinate Phosphoribosyl Transferase Expression and Expression of Profibrotic Genes

QPRT Acts as an Independent Prognostic Factor in Invasive Breast Cancer.

Background Quinolinic acid phosphoribosyltransferase (QPRT) is a rate-limiting enzyme that encodes the uronic acid pathway, which is involved in cell cycle progression and cancer cell metabolism. Some studies have demonstrated the progrowth effect of QPRT on breast cancer (BRCA) tumour cells, but its mechanism of action requires further exploration. Methods We investigated the expression of QPRT and the prognosis of patients with different tumours by performing a pan-cancer analysis of QPRT. Prognostic values for overall survival (OS) were determined using uni- and multivariate Cox proportional hazard analyses. The prognostic survival of patients with a different pathological staging of BRCA and with QPRT high and low expression was also analysed. We also explored the relevant pathways by which QPRT affected BRCA tumorigenesis by gene set enrichment analysis (GSEA) and western blotting. The impact of QPRT on the PI3K/Akt pathway was also evaluated. Results Pan-cancer analysis revealed significant QPRT expression in pan-cancer and correlated with prognosis in most tumour patients. QPRT was also highly expressed in BRCA when patients had poor prognoses, and its expression was associated with different pathological BRCA subtypes. GSEA revealed an association between BRCA progression and the cell cycle and the phosphatidylinositol 3-kinase (PI3K)/Akt signalling pathway, and this association was confirmed by western blotting. Conclusion QPRT is highly expressed in breast cancer and particularly in HER2 breast cancer. Upregulated QPRT expression is an independent predictor of breast cancer prognosis and promotes breast cancer progression by activating the PI3K/Akt signalling pathway.

A network pharmacology-based approach to explore mechanism of action of medicinal herbs for alopecia treatment

Hair loss is one of the most common skin problems experienced by more than half of the world's population. In East Asia, medicinal herbs have been used widely in clinical practice to treat hair loss. Recent studies, including systematic literature reviews, indicate that medicinal herbs may demonstrate potential effects for hair loss treatment. In a previous study, we identified medical herbs used frequently for alopecia treatment. Herein, we explored the potential novel therapeutic mechanisms of 20 vital medicinal herbs for alopecia treatment that could distinguish them from known mechanisms of conventional drugs using network pharmacology analysis methods. We determined the herb-ingredient–target protein networks and ingredient-associated protein (gene)-associated pathway networks and calculated the weighted degree centrality to define the strength of the connections. Data showed that 20 vital medicinal herbs could exert therapeutic effects on alopecia mainly mediated via regulation of various target genes and proteins, including acetylcholinesterase (AChE), phospholipase A2 (PLA2) subtypes, ecto-5-nucleotidase (NTE5), folate receptor (FR), nicotinamide N-methyltransferase (NNMT), and quinolinate phosphoribosyltransferase (QPRT). Findings regarding target genes/proteins and pathways of medicinal herbs associated with alopecia treatment offer insights for further research to better understand the pathogenesis and therapeutic mechanism of medicinal herbs for alopecia treatment with traditional herbal medicine.

Cell stress response impairs de novo NAD+ biosynthesis in the kidney.

The biosynthetic routes leading to de novo nicotinamide adenine dinucleotide (NAD+) production are involved in acute kidney injury (AKI), with a critical role for quinolinate phosphoribosyl transferase (QPRT), a bottleneck enzyme of de novo NAD+ biosynthesis. The molecular mechanisms determining reduced QPRT in AKI, and the role of impaired NAD+ biosynthesis in the progression to chronic kidney disease (CKD), are unknown. We demonstrate that a high urinary quinolinate-to-tryptophan ratio, an indirect indicator of impaired QPRT activity and reduced de novo NAD+ biosynthesis in the kidney, is a clinically applicable early marker of AKI after cardiac surgery and is predictive of progression to CKD in kidney transplant recipients. We also provide evidence that the endoplasmic reticulum (ER) stress response may impair de novo NAD+ biosynthesis by repressing QPRT transcription. In conclusion, NAD+ biosynthesis impairment is an early event in AKI embedded with the ER stress response, and persistent reduction of QPRT expression is associated with AKI to CKD progression. This finding may lead to identification of noninvasive metabolic biomarkers of kidney injury with prognostic and therapeutic implications.

Jian-Pi-Yi-Shen Formula Alleviates Chronic Kidney Disease in Two Rat Models by Modulating QPRT/NAD+/SIRT3/Mitochondrial Dynamics Pathway

Objective Jian-Pi-Yi-Shen formula (JPYSF) is a traditional Chinese herbal decoction and has been used for treating chronic kidney disease (CKD) in clinics for decades. However, the potential mechanisms have not been fully elucidated. This study was designed to test the efficacy of JPYSF in treating CKD and explore the underlying mechanism. Methods Two CKD rat models were established by 5/6 nephrectomy (5/6 Nx) and feeding with adenine-containing feed, respectively. The intervention dose of JPYSF was 10.89 g/kg/d by gastric irrigation. Renal function was assessed by serum creatinine (Scr) and blood urea nitrogen (BUN). Periodic acid-Schiff (PAS) and Masson's trichrome staining were used to evaluate renal histopathological changes. The levels of nicotinamide adenine dinucleotide (NAD+) were measured by using the enzyme-linked immunosorbent assay kit. The proteins expressions of renal fibrosis, quinolinate phosphoribosyltransferase (QPRT), sirtuin 3 (SIRT3), and mitochondrial dynamics were determined and quantified by Western blot analysis. Results The results show that administration of JPYSF significantly lowered Scr and BUN levels, improved renal tubular atrophy and interstitial fibrosis, and decreased renal extracellular matrix deposition in two CKD rat models. In addition, CKD rats exhibited suppressed QPRT/NAD+/SIRT3 signal, increased mitochondrial fission, and decreased mitochondrial fusion. JPYSF treatment promoted QPRT/NAD+/SIRT3 signal and restored mitochondrial fission/fusion balance. Conclusion In conclusion, administration of JPYSF effectively alleviated CKD progression in two rat models, which may be related with regulation of the QPRT/NAD+/SIRT3/mitochondrial dynamics pathway.

Viability of diffuse large B-cell lymphoma cells is regulated by kynurenine 3-monooxygenase activity.

Diffuse large B-cell lymphoma (DLBCL) is a clinically heterogeneous lymphoid malignancy that is the most common type of lymphoma in Japan. Previous studies have demonstrated that patients with DLBCL have a poor prognosis due to increased levels of indoleamine 2,3-dioxygnase and kynurenine (KYN). However, the roles of metabolites acting downstream of KYN and associated enzymes are not fully understood. The present study investigated the role of kynurenine 3-monooxygenase (KMO), which catalyzes the conversion of KYN to 3-hydroxykynurenine (3-HK), using serum samples from patients with DLBCL and human DLBCL cell lines with different KMO expression [STR-428 cells with high levels of KMO expression (KMOhigh) and KML-1 cells with low levels of KMO expression (KMOlow)]. Serum samples from 28 patients with DLBCL and 34 healthy volunteers were used to investigate the association between prognosis and KMO activity or 3-HK levels. Furthermore, to investigate the roles of KMO and its related metabolites, STR-428 and KML-1 cell lines, and the lymph nodes of patients with DLBCL were analyzed by reverse transcription-quantitative PCR for KMO, KYNU, 3-hydroxyanthranilate-3,4-dioxygenase and quinolinate phosphoribosyltransferase, by western blotting, and immunohistochemical or immunofluorescence staining for KMO, and by cell viability and NAD+/NADH assays. KYN pathway metabolites in serum samples were measured by HPLC. Serum 3-HK levels were regulated independently of serum KYN levels, and increased serum 3-HK levels and KMO activity were found to be associated with worse disease progression. Notably, the addition of KMO inhibitors and 3-HK negatively and positively regulated the viability of DLBCL cells, respectively. Furthermore, NAD+ levels in KMOhigh STR-428 cells were significantly higher than those in KMOlow KML-1 cells. These results suggested that 3-HK generated by KMO activity may be involved in the regulation of DLBCL cell viability via NAD+ synthesis.

Impaired Nicotinamide Adenine Dinucleotide Biosynthesis in the Kidney of Chronic Kidney Disease.

Chronic kidney disease (CKD) is a global public health problem with high morbidity and mortality. Decreased nicotinamide adenine dinucleotide (NAD+) levels were found to be associated with aging, cancer, and neurodegenerative and metabolic disorders. However, the alteration of renal NAD+ levels and biosynthesis pathways in CKD is less known. In the present study, we aimed to evaluate renal NAD+ levels and tested the expression of key enzymes in three NAD+ biosynthesis pathways in two different types of CKD rat model. CKD rat models were established by 5/6 nephrectomy (5/6 Nx) and feeding with adenine-containing feed, respectively. Renal function was assessed by serum creatinine (Scr) and blood urea nitrogen (BUN). Renal pathology was evaluated by periodic acid-Schiff (PAS) and Masson’s trichrome staining. The expression of key enzymes in three NAD+ biosynthesis pathways was determined and quantified by Western blot analysis. The results showed CKD rat models were successfully established as evidenced by increased Scr and BUN levels, upregulation of neutrophil gelatinase-associated lipocalin (NGAL), glomerular hypertrophy, and renal fibrosis. Renal NAD+ and NADH content were both declined in two CKD rat models, and NAD+ levels were negatively correlated with Scr and BUN levels in CKD rats. Three key enzymes involved in NAD+ biosynthesis were significantly downregulated in the kidney of both of the two CKD models. They were quinolinate phosphoribosyltransferase (QPRT) in the de novo pathway, nicotinamide mononucleotide adenylyltransferase 1 (NMNAT1), and NMNAT3 in the salvage pathway. Moreover, the expression of NAD+-consuming enzymes sirtuin 3 (SIRT3) and CD38 decreased significantly in CKD rats. In conclusion, NAD+ biosynthesis was significantly impaired in CKD, which may attribute to downregulation of QPRT and NMNAT 1/3.

Knockdown of Quinolinate Phosphoribosyltransferase Results in Decreased Salicylic Acid-Mediated Pathogen Resistance in Arabidopsis thaliana.

Nicotinamide adenine dinucleotide (NAD) is a pivotal coenzyme that has emerged as a central hub linking redox equilibrium and signal transduction in living cells. The homeostasis of NAD is required for plant growth, development, and adaption to environmental stresses. Quinolinate phosphoribosyltransferase (QPRT) is a key enzyme in NAD de novo synthesis pathway. T-DNA-based disruption of QPRT gene is embryo lethal in Arabidopsis thaliana. Therefore, to investigate the function of QPRT in Arabidopsis, we generated transgenic plants with decreased QPRT using the RNA interference approach. While interference of QPRT gene led to an impairment of NAD biosynthesis, the QPRT RNAi plants did not display distinguishable phenotypes under the optimal condition in comparison with wild-type plants. Intriguingly, they exhibited enhanced sensitivity to an avirulent strain of Pseudomonas syringae pv. tomato (Pst-avrRpt2), which was accompanied by a reduction in salicylic acid (SA) accumulation and down-regulation of pathogenesis-related genes expression as compared with the wild type. Moreover, oxidative stress marker genes including GSTU24, OXI1, AOX1 and FER1 were markedly repressed in the QPRT RNAi plants. Taken together, these data emphasized the importance of QPRT in NAD biosynthesis and immunity defense, suggesting that decreased antibacterial immunity through the alteration of NAD status could be attributed to SA- and reactive oxygen species-dependent pathways.

NtAIDP1, a novel NtJAZ interacting protein, binds to an AT-rich region to activate the transcription of jasmonate-inducible genes in tobacco

In plants, jasmonate ZIM-domain proteins (JAZs) act as critical regulators, interacting physically with transcription factors (TFs) and other transcriptional regulators to modulate jasmonate (JA)-responsive gene expression and participate in crosstalk with other hormone signalling pathways. Identifying novel JAZ-interacting proteins will provide new insights into JA signalling cascades in plants. Here, we performed yeast two-hybrid screening to identify 70 NtJAZ1-interacting proteins, including an A/T-rich interaction domain containing protein 1 (NtAIDP1) from JA-treated tobacco Bright Yellow-2 (BY-2) cells. NtAIDP1 is localised in the nucleus and interacts with NtJAZ1 via its C-terminal heat shock protein 20 (HSP) domain. Aside from NtJAZ1, NtAIDP1 also interacts with other JA-inducible NtJAZs, including NtJAZ2b, NtJAZ2b.2, NtJAZ5, NtJAZ7, NtJAZ11 and NtJAZ12, but not with NtJAZ3, NtJAZ3b or NtJAZ10, and interacts with NtNINJA, NtDELLA1 and NtDELLA2 in the yeast two-hybrid assay. Furthermore, NtAIDP1 binds to the AT-rich region of the GAG fragment of the putrescine N-methyltransferase 1a (NtPMT1a) promoter and activates the transcriptional activity of the GAG fragment, whereas NtMYC2a interacts with and competitively inhibits the transactivational activity of NtAIDP1 in Arabidopsis mesophyll protoplasts. Overexpression of NtAIDP1 promotes the transcription of NtPDF1.2 and NtJAZ1, but has little effect on the expression of NtPMT1a, quinolinate phosphoribosyltransferase 2 (NtQPT2), and NtMYC2a in tobacco. These results indicate that NtAIDP1 is a new component of the JA signalling pathway and is involved in JA-regulated gene expression.