CR6-interacting factor 1 deficiency reduces endothelial nitric oxide synthase activity by inhibiting biosynthesis of tetrahydrobiopterin

Abstract

Downregulation of CR6 interacting factor 1 (CRIF1) has been reported to induce mitochondrial dysfunction, resulting in reduced activity of endothelial nitric oxide synthase (eNOS) and NO production in endothelial cells. Tetrahydrobiopterin (BH4) is an important cofactor in regulating the balance between NO (eNOS coupling) and superoxide production (eNOS uncoupling). However, whether the decreased eNOS and NO production in CRIF1-deficient cells is associated with relative BH4 deficiencyinduced eNOS uncoupling remains completely unknown. Our results showed that CRIF1 deficiency increased eNOS uncoupling and depleted levels of total biopterin and BH4 by reducing the enzymes of BH4 biosynthesis (GCH-1, PTS, SPR, and DHFR) in vivo and vitro, respectively. Supplementation of CRIF1-deficient cells with BH4 significantly increased the recovery of Akt and eNOS phosphorylation and NO synthesis. In addition, scavenging ROS with MitoTEMPO treatment replenished BH4 levels by elevating levels of GCH-1, PTS, and SPR, but with no effect on the level of DHFR. Downregulation of DHFR synthesis regulators p16 or p21 in CRIF1-deficient cells partially recovered the DHFR expression. In summary, CRIF1 deficiency inhibited BH4 biosynthesis and exacerbated eNOS uncoupling. This resulted in reduced NO production and increased oxidative stress, which contributes to endothelial dysfunction and is involved in the pathogenesis of cardiovascular diseases.

Immunomodulatory effects of bee pollen on doxorubicin‐induced bone marrow/spleen immunosuppression in rat

“…Aabed et al., (2019) in a study on the protective effects of BP on propionic acid (PPA)‐induced neuro‐inflammation in a rodent model of autism showed that BP can decrease systemic IL‐6, IFN‐γ and IL‐1α alongside increase IL‐10 and TNF‐α levels thereby suppressing the inflammatory pathways mediated by cytokines leading to proliferation and activation of immune cells from BM haematopoietic progenitor (HP) cells which ameliorating the neurotoxic effects of PPA. In an in vitro study of LPS‐Induced RAW 264.7 cells, Lee et al., (2020) showed that BP, in addition to its high antioxidant properties and reduced NO content, iNOS and cyclooxygenase‐2 (COX‐2), reduced IL‐1b, IL‐6 and TNF‐α levels as inflammatory mediators in macrophages.…”

“…Colorimetric assay Abcam (Abcam Cat No: ab211083; Abcam, Cambridge, MA, USA) kits was used for measuring the serum nitric oxide synthases (NOS) activity according to the manufacturer's recommendations by using an ELISA Reader (Statfax 100, USA) at 540 nm and reported as U/ml of serum (Lee et al., 2020).…”

CRIF1 Deficiency Increased Homocysteine Production by Disrupting Dihydrofolate Reductase Expression in Vascular Endothelial Cells

“…After they were subjected to vortexing and sonication, the homogenized samples were centrifuged at 12,000× g for 15 min and the supernatant was harvested. Immunoblots were performed using 20 µg samples as described previously [ 15 ]. After electrophoresis and transferring to nitrocellulose membranes, blots were blocked using 5% skim milk over 1 h at room temperature.…”

“…Thus, CRIF1 is a potential target for mitochondrial dysfunction. CRIF1 deficiency impairs mitochondrial oxidative phosphorylation and reduces nitric oxide production while inhibiting tetrahydrobiopterin (BH4) biosynthesis enzymes such as guanosine triphosphate cyclohydrolase I, 6-pyruvoyltetrahydropterin synthase, sepiapterin reductase, and DHFR, leading to endothelial dysfunction [ 15 ]. DHFR regenerates BH4 from dihydrobiopterin and is an essential folate cycle enzyme required for homocysteine metabolism [ 16 , 17 ].…”

Nebivolol combined with tetrahydrobiopterin affects diastolic function in spontaneously hypertensive rats via the nitric oxide/cyclic guanosine monophosphate signalling pathway

“…BH4 treatment significantly increased myocardial BH4 and myocardial BH4/BH2 ratio BH4 is an important cofactor of NOS and is necessary for NO production. Insufficient BH4 leads to the decoupling of eNOS [16], generating a large amount of reactive oxygen species, which cause oxidative stress in the corresponding organs or tissues and promote heart failure. Therefore, we used high performance liquid chromatography to detect the concentration of BH4 in each group.…”