Effects of phototherapy on biopterin, neopterin, tryptophan, and behavioral neuroinflammatory reaction in patients with post-stroke depression.

The aim of this study was to investigate the overall effects of phototherapy on biopterin (BH4), neopterin (BH2), tryptophan (Trp), and behavioral neuroinflammatory reaction in patients with post-stroke depression. There involved a total of 100 hospitalized patients with post-stroke depression at our hospital from February 2021 to December 2022. The participants enrolled were randomly assigned to either the control group or the experimental group. The control group received routine treatment, including medication and psychological support, while the experimental group received 30 min of phototherapy daily for 8 weeks. All participantsvoluntarily participated in the study and provided informed consent. Baseline characteristics of the patients were statistically analyzed. The severity of depressive symptoms was evaluated using the hamilton depression scale (HAMD) and the beck depression inventory (BDI). Levels of amino acid neurotransmitters, including gamma-aminobutyric acid (GABA), aspartic acid (Asp), and glutamic acid (Glu), were measured using radioimmunoassay. Plasma levels of neuroinflammatory factors, such as TNF-α, IL-6, and IL-1ß were, determined using ELISA. Plasma levels of BH4, BH2, and Trp were detected by HPLC. Levels of SOD, GPx, CAT, and MDA in plasma were measured using corresponding kits and colorimetry. Quality of life was assessed using the SF-36 scale. There were no differences in baseline characteristic between the two groups (P > 0.05). The HAMD and BDI scores in the experimental group were lower than those in the control group (P < 0.05), indicating phototherapy could reduce the severity of post-stroke depression. The levels of GABA, Glu, and Asp in both groups significantly increased after treatment compared to their respective levels before treatment (P < 0.01).The levels of GABA in the experimental group were higher than those in the control group (P < 0.01),while the levels of Glu, and Asp were lower than those in the control group (P < 0.01). The plasma levels of TNF-α, IL-6, and IL-1ß in the experimental group were evidently lower than those in the control group (P < 0.05). Moreover, the levels of BH4 and Trp in experimental group were significantly higher than those in the control group (P < 0.05), while the levelsof BH2 in the experimental group were significantly lower than the control group (P < 0.05). Additionally, the levels of SOD, GPx, and CAT in the experimental group were evidently higher than those in the control group (P < 0.05), whereas the levels of MDA in the experimental group were significantly lower than control group (P < 0.05). The experimental group showed higher scores in physical function, mental health, social function, and overall health compared to the control group (P < 0.05). Phototherapy exerted a profound impact on the metabolism of BH4, BH2, and Trp, as well as on behavioral neuroinflammatory reactions and the quality of life in patients suffering from post-stroke depression. Through its ability to optimize the secretion and synthesis of neurotransmitters, phototherapy effectively regulated neuroinflammatory reactions, improved biochemical parameters, enhancedantioxidant capacity, and alleviated depressive symptoms. As a result, phototherapy was considered a valuable adjuvant therapeutic approach for patients with post-stroke depression.

QDPR deficiency drives immune suppression in pancreatic cancer.

The relevance of biopterin metabolism in resistance to immune checkpoint blockade (ICB) therapy remains unknown. We demonstrate that the deficiency of quinoid dihydropteridine reductase (QDPR), a critical enzyme regulating biopterin metabolism, causes metabolite dihydrobiopterin (BH2) accumulation and decreases the ratio of tetrahydrobiopterin (BH4) to BH2 in pancreatic ductal adenocarcinomas (PDACs). The reduced BH4/BH2 ratio leads to an increase in reactive oxygen species (ROS) generation and a decrease in the distribution of H3K27me3 at CXCL1 promoter. Consequently, myeloid-derived suppressor cells are recruited to tumor microenvironment via CXCR2 causing resistance to ICB therapy. We discovered that BH4 supplementation is capable to restore the BH4/BH2 ratio, enhance anti-tumor immunity, and overcome ICB resistance in QDPR-deficient PDACs. Tumors with lower QDPR expression show decreased responsiveness to ICB therapy. These findings offer a novel strategy for selecting patient and combining therapies to improve the effectiveness of ICB therapy in PDAC.

Exploring the therapeutic potential of tetrahydrobiopterin for heart failure with preserved ejection fraction: A path forward.

A large number of patients are affected by classical heart failure (HF) symptomatology with preserved ejection fraction (HFpEF) and multiorgan syndrome. Due to high morbidity and mortality rate, hospitalization and mortality remain serious socioeconomic problems, while the lack of effective pharmacological or device treatment means that HFpEF presents a major unmet medical need. Evidence from clinical and basic studies demonstrates that systemic inflammation, increased oxidative stress, and impaired mitochondrial function are the common pathological mechanisms in HFpEF. Tetrahydrobiopterin (BH4), beyond being an endogenous co-factor for catalyzing the conversion of some essential biomolecules, has the capacity to prevent systemic inflammation, enhance antioxidant resistance, and modulate mitochondrial energy production. Therefore, BH4 has emerged in the last decade as a promising agent to prevent or reverse the progression of disorders such as cardiovascular disease. In this review, we cover the clinical progress and limitations of using downstream targets of nitric oxide (NO) through NO donors, soluble guanylate cyclase activators, phosphodiesterase inhibitors, and sodium-glucose co-transporter 2 inhibitors in treating cardiovascular diseases, including HFpEF. We discuss the use of BH4 in association with HFpEF, providing new evidence for its potential use as a pharmacological option for treating HFpEF.

Binding profile of quinonoid-dihydrobiopterin to quinonoid-dihydropteridine reductase examined by in silico and in vitro analyses.

Quinonoid dihydropteridine reductase (QDPR) catalyses the reduction of quinonoid-form dihydrobiopterin (qBH2) to tetrahydrobiopterin (BH4). BH4 metabolism is a drug target for neglected tropical disorders because trypanosomatid protozoans, including Leishmania and Trypanosoma, require exogenous sources of biopterin for growth. Although QDPR is a key enzyme for maintaining intracellular BH4 levels, the precise catalytic properties and reaction mechanisms of QDPR are poorly understood due to the instability of quinonoid-form substrates. In this study, we analysed the binding profile of qBH2 to human QDPR in combination with in silico and in vitro methods. First, we performed docking simulation of qBH2 to QDPR to obtain possible binding modes of qBH2 at the active site of QDPR. Then, among them, we determined the most plausible binding mode using molecular dynamics simulations revealing its atomic-level interactions and confirmed it with the in vitro assay of mutant enzymes. Moreover, it was found that not only qBH2 but also quinonoid-form dihydrofolate (qDHF) could be potential physiological substrates for QDPR, suggesting that QDPR may be a bifunctional enzyme. These findings in this study provide important insights into biopterin and folate metabolism and would be useful for developing drugs for neglected tropical diseases.

Expression of BmDHFR is up-regulated to trigger an increase in the BH4/BH2 ratio when the de novo synthesis of BH4 is blocked in silkworm, Bombyx mori.

Tetrahydrobiopterin (BH4) is a vital coenzyme for several enzymes involved in diverse enzymatic reactions in animals. BH4 deficiency can lead to metabolic and neurological disorders due to dysfunction in its metabolism. Sepiapterin reductase (SPR) and dihydrofolate reductase (DHFR) are crucial enzymes in the BH4 de novo synthesis pathway and salvage pathway, respectively. Dihydrobiopterin (BH2) is an oxidized product of BH4 metabolism. The ratio of BH4/BH2 is a key indicator of the stability of BH4 levels. The de novo pathway of BH4 synthesis is well-defined; however, little is known about the mechanisms of the salvage pathway in insects. Herein, we used the natural BmSPR mutant silkworm (lem) as a resource material. Our results reveal that the BmDHFR expression and the BH4/BH2 ratio were remarkably higher in lem as compared to the wild-type silkworm. In BmN cells, knockdown of BmSpr showed increased BmDHFR expression, while the BH4/BH2 ratio decreased after BmDhfr knockdown by RNAi. Furthermore, simultaneous RNAi of BmSpr and BmDhfr showed a further decrease in the BH4/BH2 ratio. These manifest that the expression of BmDHFR is up-regulated to trigger an increase in the BH4/BH2 ratio when the de novo synthesis of BH4 is blocked in silkworm. Additionally, the knockdown of BmSpr in wild-type silkworms also showed an increased BmDHFR level and BH4/BH2 ratio. Taken together, when the silkworm BH4 de novo synthesis pathway is blocked, the salvage pathway is activated, and BmDHFR plays an important role in maintaining the metabolic balance of silkworm BH4. This study enriches our understanding of the molecular mechanism of the BH4 salvage pathway and lays a good foundation for further studies on BH4 using the silkworm as a model insect.

No effect of acute tetrahydrobiopterin (BH4) supplementation on vascular dysfunction in the old.

As a deficiency in tetrahydrobiopterin (BH4), a cofactor for endothelial nitric oxide synthase, has been implicated in the age-related decline in vascular function, this study aimed to determine the impact of acute BH4 supplementation on flow-mediated vasodilation (FMD) in old adults. Two approaches were used: 1) A multiday, double-blind, placebo-controlled, crossover design measuring, FMD [ΔFMD (mm), %FMD (%)] and shear rate area under the curve (SR AUC) in nine old subjects (73 ± 8 yr) with either placebo (placebo) or BH4 (≈10 mg/kg, post), and 2) a single experimental day measuring FMD in an additional 13 old subjects (74 ± 7 yr) prior to (pre) and 4.5 h after ingesting BH4 (≈10 mg/kg). With the first experimental approach, acute BH4 intake did not significantly alter FMD (ΔFMD: 0.17 ± 0.03 vs. 0.13 ± 0.02 mm; %FMD: 3.3 ± 0.61 vs. 2.9 ± 0.4%) or SR AUC (30,280 ± 4,428 vs. 37,877 ± 9,241 s-1) compared with placebo. Similarly, with the second approach, BH4 did not significantly alter FMD (ΔFMD: 0.09 ± 0.02 vs. 0.12 ± 0.03 mm; %FMD: 2.2 ± 0.6 vs. 2.9 ± 0.6%) or SR AUC (37,588 ± 6,753 vs. 28,996 ± 3,735 s-1) compared with pre. Moreover, when the two data sets were combined, resulting in a greater sample size, there was still no evidence of an effect of BH4 on vascular function in these old subjects. Importantly, both plasma BH4 and 7,8-dihydrobiopterin (BH2), the oxidized form of BH4, increased significantly with acute BH4 supplementation. Consequently, the ratio of BH4/BH2, recognized to impact vascular function, was unchanged. Thus, acute BH4 supplementation does not correct vascular dysfunction in the old.NEW & NOTEWORTHY Despite two different experimental approaches, acute BH4 supplementation did not affect vascular function in older adults, as measured by flow-mediated vasodilation. Plasma levels of both BH4 and BH2, the BH4 oxidized form, significantly increased after acute BH4 supplementation, resulting in an unchanged ratio of BH4/BH2, a key determining factor for endothelial nitric oxide synthase coupling. Therefore, likely due to the elevated oxidative stress with advancing age, acute BH4 supplementation does not correct vascular dysfunction in the old.

Aging increases circulating BH2 without modifying BH4 levels and impairs peripheral vascular function in healthy adults.

Little is known about the mechanisms of aging on vascular beds and its relationship with tetra and di-hydrobiopterin (BH4 and BH2) levels. This observational clinical study analyzed the impact of aging on plasma and platelet biopterins, cutaneous blood flow (CBF), and coronary flow reserve (CFR) in healthy adults. The study enrolled healthy adults in 3 age groups: 18-30, 50-59, and 60-70 years (n = 25/group). Biopterins were assessed by LC-MS/MS using newly defined pre-analytical conditions limiting BH4 oxidation and improving long-term stability. CBF was measured by Laser Speckle Contrast Imaging coupled with acetylcholine-iontophoresis and CFR by adenosine stress cardiac magnetic resonance. In healthy adults, aging (60-70 years vs 18-30 years) significantly increased platelet BH2 (+75%, P = 0.033) and BH2 + BH4 (+31%, P = 0.033), and to a lesser extent plasma BH2 (+29%, P = 0.009) without affecting BH4 and BH4/BH2. Simultaneously, CBF was decreased (-23%, P = 0.004) but not CFR, CBF being inversely correlated with platelet BH2 (r = -0.42, P = 0.001) and BH2 + BH4 (r = -0.41, P = 0.002). The proportion of adults with abnormal platelet BH2 increased with age (+28% in 60-70y). These abnormal BH2 levels were significantly associated with reduced CBF and CFR (-16%, P = 0.03 and -26%, P = 0.02). In conclusion, our study showed that age-related peripheral endothelial dysfunction was associated with an increase in circulating BH2 without decreasing BH4, the effect being more marked in platelets, the most relevant blood compartment to assess biopterin bioavailability. Peripheral but not coronary vascular function is progressively impaired with aging in healthy adults. All these findings support biopterins as therapeutic targets to improve vascular function.

Co-ingestion of whole eggs or egg whites with glucose protects against postprandial hyperglycaemia-induced oxidative stress and dysregulated arginine metabolism in association with improved vascular endothelial function in prediabetic men.

Replacing a portion of a glucose challenge with whole eggs (EGG) or egg whites (WHITE) was shown to protect against glucose-induced impairments in vascular function. We hypothesised in the present study that previously observed vasoprotection following co-ingestion of EGG or WHITE with glucose was attributed to limiting postprandial hyperglycaemia-induced oxidative stress that improves NO∙ bioavailability. Prediabetic men completed a randomised, cross-over study in which they ingested isoenergetic meals containing 100 g glucose (GLU), or 75 g glucose with 1·5 EGG, seven WHITE or two egg yolks (YOLK). At 30 min intervals for 3 h, we assessed plasma NO∙ metabolites, the lipid peroxidation biomarker malondialdehyde, antioxidants, arginine and its methylated metabolites (asymmetric dimethylarginine and symmetric dimethylarginine), tetrahydrobiopterin redox status, vasoconstrictors and inflammatory markers. Compared with GLU, malondialdehyde was lower and NO∙ metabolites were greater in EGG and WHITE, but YOLK was not different from GLU. Malondialdehyde was inversely correlated with NO∙ metabolites and vascular function, whereas NO∙ metabolites were positively correlated with vascular function. Compared with GLU, arginine was greater, but asymmetric and symmetric dimethylarginine and angiotensin-II were lower in all egg-based meals. Antioxidants, tetrahydrobiopterin redox status and inflammatory markers did not differ among treatments. Thus, while each egg-based meal improved arginine metabolism, only EGG and WHITE limited lipid peroxidation. This suggests that vasoprotection mediated by EGG and WHITE likely occurs in an NO∙-dependent manner by improving arginine metabolism and attenuating oxidative stress that otherwise limit NO∙ biosynthesis and bioavailability to the vascular endothelium.

l-Phenylalanine Restores Vascular Function in Spontaneously Hypertensive Rats Through Activation of the GCH1-GFRP Complex.

Reduced nitric oxide (NO) bioavailability correlates with impaired cardiovascular function. NO is extremely labile and has been challenging to develop as a therapeutic agent. However, NO bioavailability could be enhanced by pharmacologically targeting endogenous NO regulatory pathways. Tetrahydrobiopterin, an essential cofactor for NO production, is synthesized by GTP cyclohydrolase-1 (GCH1), which complexes with GCH1 feedback regulatory protein (GFRP). The dietary amino acid l-phenylalanine activates this complex, elevating vascular BH4. Here, the authors demonstrate that l-phenylalanine administration restores vascular function in a rodent model of hypertension, suggesting the GCH1-GFRP complex represents a rational therapeutic target for diseases underpinned by endothelial dysfunction.

Guinea pig ascorbate status predicts tetrahydrobiopterin plasma concentration and oxidation ratio in vivo.

Tetrahydrobiopterin (BH4) is an essential co-factor of nitric oxide synthases and is easily oxidized to dihydrobiopterin (BH2) which promotes endothelial nitric oxide synthase uncoupling and deleterious superoxide production. Vitamin C has been shown to improve endothelial function by different mechanisms, some involving BH4. The hypothesis of the present study was that vitamin C status, in particular low levels, influences biopterin redox status in vivo. Like humans, the guinea pig lacks the ability to synthesize vitamin C and was therefore used as model. Seven day old animals (n = 10/group) were given a diet containing 100, 250, 500, 750, 1000, or 1500 ppm vitamin C until euthanasia at age 60-64 days. Blood samples were drawn from the heart and analyzed for ascorbate, dehydroascorbic acid (DHA), BH4 and BH2 by high-performance liquid chromatography. Plasma BH4 levels were found to be significantly lower in animals fed 100 ppm vitamin C compared to all other groups (P < .05 or less). BH2 levels were not significantly different between groups but the BH2-to-BH4 ratio was higher in the group fed 100 ppm vitamin C (P < .001 all cases). Significant positive correlations between BH4 and ascorbate and between BH2-to-BH4 ratio and DHA were observed (P < .0001 both cases). Likewise, BH2-to-BH4 ratio was negatively correlated with ascorbate (P < .0001) as was BH4 and DHA (P < .005). In conclusion, the redox status of plasma biopterins, essentially involved in vasodilation, depends on the vitamin C status in vivo. Thus, ingestion of insufficient quantities of vitamin C not only leads to vitamin C deficiency but also to increased BH4 oxidation which may promote endothelial dysfunction.

Alzheimer's disease treated patients showed different patterns for oxidative stress and inflammation markers.

Alzheimer's disease (AD) is the most common type of dementia accounting for 60-80% of the reported cases. The aim of this study was to evaluate levels of certain parameters of oxidative stress and markers of endothelial dysfunction in the blood of 21 AD patients under standard treatment compared with 10 controls, in an attempt to elucidate the contribution of AD to the total oxidative stress status of the patients. Results indicate that IL-6, TNF-α, ADMA and homocysteine levels were significantly elevated in AD patients. Protein carbonyls levels were higher in AD group, while glutathione reductase and total antioxidant capacity were lower, depicting decreased defense ability against reactive oxygen species. Besides, a higher level of advanced glycation end-products was observed in AD patients. Depending on the treatment received, a distinct inflammatory and oxidative stress profile was observed: in Rivastigmine-treated group, IL6 levels were 47% lower than the average value of the remaining AD patients; homocysteine and glutathione reductase were statistically unchanged in the Rivastigmine and Donepezil-Memantine, respectively Donepezil group. Although the study is based on a limited population, the results could constitute the basis for further studies regarding the effect of medication and diet on AD patients.

Cardiac oxidative stress in a mouse model of neutral lipid storage disease.

Cardiac oxidative stress has been implicated in the pathogenesis of hypertrophy, cardiomyopathy and heart failure. Systemic deletion of the gene encoding adipose triglyceride lipase (ATGL), the enzyme that catalyzes the rate-limiting step of triglyceride lipolysis, results in a phenotype characterized by severe steatotic cardiac dysfunction. The objective of the present study was to investigate a potential role of oxidative stress in cardiac ATGL deficiency. Hearts of mice with global ATGL knockout were compared to those of mice with cardiomyocyte-restricted overexpression of ATGL and to those of wildtype littermates. Our results demonstrate that oxidative stress, measured as lucigenin chemiluminescence, was increased ~6-fold in ATGL-deficient hearts. In parallel, cytosolic NADPH oxidase subunits p67phox and p47phox were upregulated 4-5-fold at the protein level. Moreover, a prominent upregulation of different inflammatory markers (tumor necrosis factor α, monocyte chemotactant protein-1, interleukin 6, and galectin-3) was observed in those hearts. Both the oxidative and inflammatory responses were abolished upon cardiomyocyte-restricted overexpression of ATGL. Investigating the effect of oxidative and inflammatory stress on nitric oxide/cGMP signal transduction we observed a ~2.5-fold upregulation of soluble guanylate cyclase activity and a ~2-fold increase in cardiac tetrahydrobiopterin levels. Systemic treatment of ATGL-deficient mice with the superoxide dismutase mimetic Mn(III)tetrakis (4-benzoic acid) porphyrin did not ameliorate but rather aggravated cardiac oxidative stress. Our data suggest that oxidative and inflammatory stress seems involved in lipotoxic heart disease. Upregulation of soluble guanylate cyclase and cardiac tetrahydrobiopterin might be regarded as counterregulatory mechanisms in cardiac ATGL deficiency.

Heat-induced fibrillation of BclXL apoptotic repressor.

The BclXL apoptotic repressor bears the propensity to associate into megadalton oligomers in solution, particularly under acidic pH. Herein, using various biophysical methods, we analyze the effect of temperature on the oligomerization of BclXL. Our data show that BclXL undergoes irreversible aggregation and assembles into highly-ordered rope-like homogeneous fibrils with length in the order of mm and a diameter in the µm-range under elevated temperatures. Remarkably, the formation of such fibrils correlates with the decay of a largely α-helical fold into a predominantly ß-sheet architecture of BclXL in a manner akin to the formation of amyloid fibrils. Further interrogation reveals that while BclXL fibrils formed under elevated temperatures show no observable affinity toward BH3 ligands, they appear to be optimally primed for insertion into cardiolipin bicelles. This salient observation strongly argues that BclXL fibrils likely represent an on-pathway intermediate for insertion into mitochondrial outer membrane during the onset of apoptosis. Collectively, our study sheds light on the propensity of BclXL to form amyloid-like fibrils with important consequences on its mechanism of action in gauging the apoptotic fate of cells in health and disease.