Proline biosynthesis is a vent for TGFß-induced mitochondrial redox stress.

The production and secretion of matrix proteins upon stimulation of fibroblasts by transforming growth factor-beta (TGFß) play a critical role in wound healing. How TGFß supports the bioenergetic cost of matrix protein synthesis is not fully understood. Here, we show that TGFß promotes protein translation at least in part by increasing the mitochondrial oxidation of glucose and glutamine carbons to support the bioenergetic demand of translation. Surprisingly, we found that in addition to stimulating the entry of glucose and glutamine carbon into the TCA cycle, TGFß induced the biosynthesis of proline from glutamine in a Smad4-dependent fashion. Metabolic manipulations that increased mitochondrial redox generation promoted proline biosynthesis, while reducing mitochondrial redox potential and/or ATP synthesis impaired proline biosynthesis. Thus, proline biosynthesis acts as a redox vent, preventing the TGFß-induced increase in mitochondrial glucose and glutamine catabolism from generating damaging reactive oxygen species (ROS) when TCA cycle activity exceeds the ability of oxidative phosphorylation to convert mitochondrial redox potential into ATP. In turn, the enhanced synthesis of proline supports TGFß-induced production of matrix proteins.

Vitamin B6 Addiction in Acute Myeloid Leukemia.

Cancer cells rely on altered metabolism to support abnormal proliferation. We performed a CRISPR/Cas9 functional genomic screen targeting metabolic enzymes and identified PDXK-an enzyme that produces pyridoxal phosphate (PLP) from vitamin B6-as an acute myeloid leukemia (AML)-selective dependency. PDXK kinase activity is required for PLP production and AML cell proliferation, and pharmacological blockade of the vitamin B6 pathway at both PDXK and PLP levels recapitulated PDXK disruption effects. PDXK disruption reduced intracellular concentrations of key metabolites needed for cell division. Furthermore, disruption of PLP-dependent enzymes ODC1 or GOT2 selectively inhibited AML cell proliferation and their downstream products partially rescued PDXK disruption induced proliferation blockage. Our work identifies the vitamin B6 pathway as a pharmacologically actionable dependency in AML.

Comparison of Topical and Intravenous Tranexamic Acid for Total Knee Replacement: A Randomized Double-Blinded Controlled Study of Effects on Tranexamic Acid Levels and Thrombogenic and Inflammatory Marker Levels.

BACKGROUND: Tranexamic acid (TXA) is an antifibrinolytic drug. Topical administration of TXA during total knee arthroplasty (TKA) is favored for certain patients because of concerns about thrombotic complications, despite a lack of supporting literature. We compared local and systemic levels of thrombogenic markers, interleukin (IL)-6, and TXA between patients who received intravenous (IV) TXA and those who received topical TXA. METHODS: Seventy-six patients scheduled for TKA were enrolled in this randomized double-blinded study. The IV group received 1.0 g of IV TXA before tourniquet inflation and again 3 hours later; a topical placebo was administered 5 minutes before final tourniquet release. The topical group received an IV placebo before tourniquet inflation and again 3 hours later; 3.0 g of TXA was administered topically 5 minutes before final tourniquet release. Peripheral and wound blood samples were collected to measure levels of plasmin-anti-plasmin (PAP, a measure of fibrinolysis), prothrombin fragment 1.2 (PF1.2, a marker of thrombin generation), IL-6, and TXA. RESULTS: At 1 hour after tourniquet release, systemic PAP levels were comparable between the IV group (after a single dose of IV TXA) and the topical group. At 4 hours after tourniquet release, the IV group had lower systemic PAP levels than the topical group (mean and standard deviation, 1,117.8 ± 478.9 µg/L versus 1,280.7 ± 646.5 µg/L; p = 0.049), indicative of higher antifibrinolytic activity after the second dose. There was no difference in PF1.2 levels between groups, indicating that there was no increase in thrombin generation. The IV group had higher TXA levels at all time points (p < 0.001). Four hours after tourniquet release, wound blood IL-6 and TXA levels were higher than systemic levels in both groups (p < 0.001). Therapeutic systemic TXA levels (mean, 7.2 ± 7.4 mg/L) were noted in the topical group. Calculated blood loss and the length of the hospital stay were lower in the IV group (p = 0.026 and p = 0.025). CONCLUSIONS: Given that therapeutic levels were reached with topical TXA and the lack of a major difference in the mechanism of action, coagulation, and fibrinolytic profile between topical TXA and a single dose of IV TXA, it may be a simpler protocol for institutions to adopt the use of a single dose of IV TXA when safety is a concern. LEVEL OF EVIDENCE: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Transsulfuration Activity Can Support Cell Growth upon Extracellular Cysteine Limitation.

Cysteine acts both as a building unit for protein translation and as the limiting substrate for glutathione synthesis to support the cellular antioxidant system. In addition to transporter-mediated uptake, cellular cysteine can also be synthesized from methionine through the transsulfuration pathway. Here, we investigate the regulation of transsulfuration and its role in sustaining cell proliferation upon extracellular cysteine limitation, a condition reported to occur in human tumors as they grow in size. We observed constitutive expression of transsulfuration enzymes in a subset of cancer cell lines, while in other cells, these enzymes are induced following cysteine deprivation. We show that both constitutive and inducible transsulfuration activities contribute to the cellular cysteine pool and redox homeostasis. The rate of transsulfuration is determined by the cellular capacity to conduct methylation reactions that convert S-adenosylmethionine to S-adenosylhomocysteine. Finally, our results demonstrate that transsulfuration-mediated cysteine synthesis is critical in promoting tumor growth in vivo.

Microbiota-derived lantibiotic restores resistance against vancomycin-resistant Enterococcus.

Intestinal commensal bacteria can inhibit dense colonization of the gut by vancomycin-resistant Enterococcus faecium (VRE), a leading cause of hospital-acquired infections1,2. A four-strained consortium of commensal bacteria that contains Blautia producta BPSCSK can reverse antibiotic-induced susceptibility to VRE infection3. Here we show that BPSCSK reduces growth of VRE by secreting a lantibiotic that is similar to the nisin-A produced by Lactococcus lactis. Although the growth of VRE is inhibited by BPSCSK and L. lactis in vitro, only BPSCSK colonizes the colon and reduces VRE density in vivo. In comparison to nisin-A, the BPSCSK lantibiotic has reduced activity against intestinal commensal bacteria. In patients at high risk of VRE infection, high abundance of the lantibiotic gene is associated with reduced density of E. faecium. In germ-free mice transplanted with patient-derived faeces, resistance to VRE colonization correlates with abundance of the lantibiotic gene. Lantibiotic-producing commensal strains of the gastrointestinal tract reduce colonization by VRE and represent potential probiotic agents to re-establish resistance to VRE.

Sensitive, accurate and simple liquid chromatography-tandem mass spectrometric method for the quantitation of amphotericin B in human or minipig plasma.

Amphotericin B (AMB) is still the standard care for systemic fungal infections. This paper describes a sensitive, accurate and simple liquid chromatography-tandem mass spectrometry method to quantify AMB in human or minipig plasma. Samples were prepared through protein precipitation by adding methanol-acetonitrile (1:3, v/v) to either human or minipig plasma. High-performance liquid chromatography separation was conducted on a 10-cm Gemini C18 column with a 7-min gradient of mobile phase comprised of buffer A (0.1% formic acid aqueous solution) and buffer B (methanol-acetonitrile, 2:3, v/v). AMB was detected through multiple reaction monitoring (MRM) with a mass transition of 924.60 → 743.30 and the internal standard paclitaxel was detected through MRM with a mass transition of 854.30 → 286.10. The method had a linear range between 5 and 2500 ng/mL with lower limit of quantitation of 3 ng/mL. The overall recovery was 113 ± 4.06% in human plasma and 94.8 ± 7.38% in minipig plasma. The method has been validated and applied for AMB pharmacokinetic study in both human and minipig plasma.