Phosphatidic acid species 34:1 mediates expression of the myo-inositol 3-phosphate synthase gene INO1 for lipid synthesis in yeast.

Depletion of exogenous inositol in yeast results in rising levels of phosphatidic acid (PA) and is correlated with increased expression of genes containing the inositol-dependent upstream activating sequence promoter element (UASINO). INO1, encoding myo-inositol 3-phosphate synthase, is the most highly regulated of the inositol-dependent upstream activating sequence-containing genes, but its mechanism of regulation is not clear. In the current study, we determined the relative timing and kinetics of appearance of individual molecular species of PA following removal of exogenous inositol in actively growing wild type, pah1Δ, and ole1ts strains. We report that the pah1Δ strain, lacking the PA phosphatase, exhibits a delay of about 60 min in comparison to wildtype before initiating derepression of INO1 expression. The ole1ts mutant on the other hand, defective in fatty acid desaturation, when grown at a semirestrictive temperature, exhibited reduced synthesis of PA species 34:1 and elevated synthesis of PA species 32:1. Importantly, we found these changes in the fatty acid composition in the PA pool of the ole1ts strain were associated with reduced expression of INO1, indicating that synthesis of PA 34:1 is involved in optimal expression of INO1 in the absence of inositol. Using deuterium-labeled glycerol in short-duration labeling assays, we found that changes associated with PA species 34:1 were uniquely correlated with increased expression of INO1 in all three strains. These data indicate that the signal for activation of INO1 transcription is not necessarily the overall level of PA but rather levels of a specific species of newly synthesized PA 34:1.

The yeast FIT2 homologs are necessary to maintain cellular proteostasis and membrane lipid homeostasis.

Lipid droplets (LDs) are implicated in conditions of lipid and protein dysregulation. The fat storage-inducing transmembrane (FIT; also known as FITM) family induces LD formation. Here, we establish a model system to study the role of the Saccharomyces cerevisiae FIT homologues (ScFIT), SCS3 and YFT2, in the proteostasis and stress response pathways. While LD biogenesis and basal endoplasmic reticulum (ER) stress-induced unfolded protein response (UPR) remain unaltered in ScFIT mutants, SCS3 was found to be essential for proper stress-induced UPR activation and for viability in the absence of the sole yeast UPR transducer IRE1 Owing to not having a functional UPR, cells with mutated SCS3 exhibited an accumulation of triacylglycerol within the ER along with aberrant LD morphology, suggesting that there is a UPR-dependent compensatory mechanism that acts to mitigate lack of SCS3 Additionally, SCS3 was necessary to maintain phospholipid homeostasis. Strikingly, global protein ubiquitylation and the turnover of both ER and cytoplasmic misfolded proteins is impaired in ScFITΔ cells, while a screen for interacting partners of Scs3 identifies components of the proteostatic machinery as putative targets. Together, our data support a model where ScFITs play an important role in lipid metabolism and proteostasis beyond their defined roles in LD biogenesis.This article has an associated First Person interview with the first author of the paper.

Comparison of Inhibitor and Substrate Selectivity between Rodent and Human Vascular Adhesion Protein-1.

Vascular adhesion protein-1 (VAP-1) is an ectoenzyme that functions as a copper-containing amine oxidase and is involved in leukocyte adhesion at sites of inflammation. Inhibition of VAP-1 oxidative deamination has become an attractive target for anti-inflammatory therapy with demonstrated efficacy in rodent models of inflammation. A previous comparison of purified recombinant VAP-1 from mouse, rat, monkey, and human gene sequences predicted that rodent VAP-1 would have higher affinity for smaller hydrophilic substrates/inhibitors because of its narrower and more hydrophilic active site channel. An optimized in vitro oxidative deamination fluorescence assay with benzylamine (BA) was used to compare inhibition of five known inhibitors in recombinant mouse, rat, and human VAP-1. Human VAP-1 was more sensitive compared to rat or mouse VAP-1 (lowest IC50 concentration) to semicarbazide but was least sensitive to hydralazine and LJP-1207. Hydralazine had a lower IC50 in rats compared to humans, although not significant. However, the IC50 of hydralazine was significantly higher in the rat compared to mouse VAP-1. The larger hydrophobic compounds from Astellas (compound 35c) and Boehringer Ingelheim (PXS-4728A) were hypothesized to have higher binding affinity for human VAP-1 compared to rodent VAP-1 since the channel in human VAP-1 is larger and more hydrophobic than that in rodent VAP-1. Although the sensitivity of these two inhibitors was the lowest in the mouse enzyme, we found no significant differences between mouse, rat, and human VAP-1. Michaelis-Menten kinetics of the small primary amines phenylethylamine and tyramine were also compared to the common marker substrate BA demonstrating that BA had the highest affinity among the substrates. Rat VAP-1 had the highest affinity for all three substrates and mouse VAP-1 had intermediate affinity for BA and phenylethylamine, but tyramine was not a substrate for mouse VAP-1 under these assay conditions. These results suggest that comparing oxidative deamination in mouse and rat VAP-1 may be important if using these species for preclinical efficacy models.

Lipid metabolic changes in an early divergent fungus govern the establishment of a mutualistic symbiosis with endobacteria.

The recent accumulation of newly discovered fungal-bacterial mutualisms challenges the paradigm that fungi and bacteria are natural antagonists. To understand the mechanisms that govern the establishment and maintenance over evolutionary time of mutualisms between fungi and bacteria, we studied a symbiosis of the fungus Rhizopus microsporus (Mucoromycotina) and its Burkholderia endobacteria. We found that nonhost R. microsporus, as well as other mucoralean fungi, interact antagonistically with endobacteria derived from the host and are not invaded by them. Comparison of gene expression profiles of host and nonhost fungi during interaction with endobacteria revealed dramatic changes in expression of lipid metabolic genes in the host. Analysis of the host lipidome confirmed that symbiosis establishment was accompanied by specific changes in the fungal lipid profile. Diacylglycerol kinase (DGK) activity was important for these lipid metabolic changes, as its inhibition altered the fungal lipid profile and caused a shift in the host-bacterial interaction into an antagonism. We conclude that adjustments in host lipid metabolism during symbiosis establishment, mediated by DGKs, are required for the mutualistic outcome of the Rhizopus-Burkholderia symbiosis. In addition, the neutral and phospholipid profiles of R. microsporus provide important insights into lipid metabolism in an understudied group of oleaginous Mucoromycotina. Lastly, our study revealed that the DGKs involved in the symbiosis form a previously uncharacterized clade of DGK domain proteins.

Randomized pilot trial of Web-based cognitive-behavioral therapy adapted for use in office-based buprenorphine maintenance.

Background: Despite the clear success of office-based buprenorphine treatment in increasing availability of effective treatment for opioid use disorder, constraints on its effectiveness include high attrition and limited high-quality behavioral care in many areas. Web-based interventions may be a novel strategy for providing evidence-based behavioral care to individuals receiving office-based buprenorphine maintenance. This report describes modification and initial pilot testing of Web-based training in cognitive-behavioral therapy (CBT4CBT) specifically for use with individuals in office-based buprenorphine. Methods: Twelve-week randomized pilot trial evaluating effects of CBT4CBT-Buprenophine in retaining participants and reducing drug use with respect to standard office-based buprenorphine alone was carried out. Twenty individuals meeting DSM-5 (Diagnostic and Statistical Manual of Mental Disorders, 5th Edition) criteria for current opioid use disorder were randomized to standard buprenorphine treatment or buprenorphine plus access to CBT4CBT-Buprenorphine. Results: There were promising findings regarding rates of urine toxicology screens negative for opioids (91% versus 64%; P = .05, effect size d = 0.88) and all drugs (82% versus 30%; P = .004, d = 1.2). Individuals randomized to CBT4CBT-Buprenorphine completed a mean of 82.6 (SD = 4.4) days of treatment (of a possible 84) compared with 68.6 (SD = 32.6) for those assigned to standard buprenorphine treatment. Conclusions: Although preliminary and limited by the small sample size, this trial suggests the feasibility and promise of validated, Web-based interventions, tailored for this specific patient population, for improving outcomes in office-based buprenorphine.

Interaction between repressor Opi1p and ER membrane protein Scs2p facilitates transit of phosphatidic acid from the ER to mitochondria and is essential for INO1 gene expression in the presence of choline.

In the yeast Saccharomyces cerevisiae, the Opi1p repressor controls the expression of INO1 via the Opi1p/Ino2p-Ino4p regulatory circuit. Inositol depletion favors Opi1p interaction with both Scs2p and phosphatidic acid at the endoplasmic reticulum (ER) membrane. Inositol supplementation, however, favors the translocation of Opi1p from the ER into the nucleus, where it interacts with the Ino2p-Ino4p complex, attenuating transcription of INO1 A strain devoid of Scs2p (scs2Δ) and a mutant, OPI1FFAT, lacking the ability to interact with Scs2p were utilized to examine the specific role(s) of the Opi1p-Scs2p interaction in the regulation of INO1 expression and overall lipid metabolism. Loss of the Opi1p-Scs2p interaction reduced INO1 expression and conferred inositol auxotrophy. Moreover, inositol depletion in strains lacking this interaction resulted in Opi1p being localized to sites of lipid droplet formation, coincident with increased synthesis of triacylglycerol. Supplementation of choline to inositol-depleted growth medium led to decreased TAG synthesis in all three strains. However, in strains lacking the Opi1p-Scs2p interaction, Opi1p remained in the nucleus, preventing expression of INO1 These data support the conclusion that a specific pool of phosphatidic acid, associated with lipid droplet formation in the perinuclear ER, is responsible for the initial rapid exit of Opi1p from the nucleus to the ER and is required for INO1 expression in the presence of choline. Moreover, the mitochondria-specific phospholipid, cardiolipin, was significantly reduced in both strains compromised for Opi1p-Scs2p interaction, indicating that this interaction is required for the transfer of phosphatidic acid from the ER to the mitochondria for cardiolipin synthesis.

Activation of protein kinase C-mitogen-activated protein kinase signaling in response to inositol starvation triggers Sir2p-dependent telomeric silencing in yeast.

Depriving wild type yeast of inositol, a soluble precursor for phospholipid, phosphoinositide, and complex sphingolipid synthesis, activates the protein kinase C (PKC)-MAPK signaling pathway, which plays a key role in the activation of NAD(+)-dependent telomeric silencing. We now report that triggering PKC-MAPK signaling by inositol deprivation or by blocking inositol-containing sphingolipid synthesis with aureobasidin A results in increased telomeric silencing regulated by the MAPK, Slt2p, and the NAD(+)-dependent deacetylase, Sir2p. Consistent with the dependence on NAD(+) in Sir2p-regulated silencing, we found that inositol depletion induces the expression of BNA2, which is required for the de novo synthesis of NAD(+). Moreover, telomeric silencing is greatly reduced in bna2Δ and npt1Δ mutants, which are defective in de novo and salvage pathways for NAD(+) synthesis, respectively. Surprisingly, however, omitting nicotinic acid from the growth medium, which reduces cellular NAD(+) levels, leads to increased telomeric silencing in the absence of inositol and/or at high temperature. This increase in telomeric silencing in response to inositol starvation is correlated to chronological life span extension but is Sir2p-independent. We conclude that activation of the PKC-MAPK signaling by interruption of inositol sphingolipid synthesis leads to increased Sir2p-dependent silencing and is dependent upon the de novo and salvage pathways for NAD(+) synthesis but is not correlated with cellular NAD(+) levels.

Results of a pilot randomised controlled trial to measure the clinical and cost effectiveness of peer support in increasing hope and quality of life in mental health patients discharged from hospital in the UK.

BACKGROUND: Mental health patients can feel anxious about losing the support of staff and patients when discharged from hospital and often discontinue treatment, experience relapse and readmission to hospital, and sometimes attempt suicide. The benefits of peer support in mental health services have been identified in a number of studies with some suggesting clinical and economic gains in patients being discharged. METHODS: This pilot randomised controlled trial with economic evaluation aimed to explore whether peer support in addition to usual aftercare for patients during the transition from hospital to home would increase hope, reduce loneliness, improve quality of life and show cost effectiveness compared with patients receiving usual aftercare only, with follow-up at one and three-months post-discharge. RESULTS: A total of 46 service users were recruited to the study; 23 receiving peer support and 23 in the care-as-usual arm. While this pilot trial found no statistically significant benefits for peer support on the primary or secondary outcome measures, there is an indication that hope may be further increased in those in receipt of peer support. The total cost per case for the peer support arm of the study was £2154 compared to £1922 for the control arm. The mean difference between costs was minimal and not statistically significant. However, further analyses demonstrated that peer support has a reasonably high probability of being more cost effective for a modest positive change in the measure of hopelessness. Challenges faced in recruitment and follow-up are explored alongside limitations in the delivery of peer support. CONCLUSIONS: The findings suggest there is merit in conducting further research on peer support in the transition from hospital to home consideration should be applied to the nature of the patient population to whom support is offered; the length and frequency of support provided; and the contact between peer supporters and mental health staff. There is no conclusive evidence to support the cost effectiveness of providing peer support, but neither was it proven a costly intervention to deliver. The findings support an argument for a larger scale trial of peer support as an adjunct to existing services. TRIAL REGISTRATION: Current Controlled Trials ISRCTN74852771.

Evaluating the selection, training, and support of peer support workers in the United Kingdom.

This article describes the preparation, selection, training, and support of a group of people with lived experience of mental distress/illness and mental health service use to work as peer support workers (PSWs). The PSWs were recruited to provide support alongside conventional aftercare to service users discharged from acute psychiatric units in London, England. Training was delivered over 12 weekly, 1-day sessions from April to July 2010. Supervision and support were provided by a peer support coordinator and a training facilitator. The overall view of the training by those who went on to work as PSWs was that it was a valuable, challenging, yet positive experience that provided them with a good preparation for the role. A key area for improvement concerned the strength of emotional involvement and feelings PSWs had for their peers, especially in regard to ending the support relationship. Skilled, sensitive supervision and support is essential for the success of such roles.

Diversity must start somewhere: the experience of one college of nursing.

The concept of diversity varies widely in its definition, conceptualization and connotations. Addressing issues of diversity within a college of nursing is necessary if the cultures of our academic units are to change and become more inclusive. The article provides an overview of how this CON began to address changing its culture to one of a more inclusive nature and across all groups represented within the college, not bound only by ethnicity and gender. The process described in this article may provide an example for others to follow.

Coordination of storage lipid synthesis and membrane biogenesis: evidence for cross-talk between triacylglycerol metabolism and phosphatidylinositol synthesis.

Despite the importance of triacylglycerols (TAG) and steryl esters (SE) in phospholipid synthesis in cells transitioning from stationary-phase into active growth, there is no direct evidence for their requirement in synthesis of phosphatidylinositol (PI) or other membrane phospholipids in logarithmically growing yeast cells. We report that the dga1Δlro1Δare1Δare2Δ strain, which lacks the ability to synthesize both TAG and SE, is not able to sustain normal growth in the absence of inositol (Ino(-) phenotype) at 37 °C especially when choline is present. Unlike many other strains exhibiting an Ino(-) phenotype, the dga1Δlro1Δare1Δare2Δ strain does not display a defect in INO1 expression. However, the mutant exhibits slow recovery of PI content compared with wild type cells upon reintroduction of inositol into logarithmically growing cultures. The tgl3Δtgl4Δtgl5Δ strain, which is able to synthesize TAG but unable to mobilize it, also exhibits attenuated PI formation under these conditions. However, unlike dga1Δlro1Δare1Δare2Δ, the tgl3Δtgl4Δtgl5Δ strain does not display an Ino(-) phenotype, indicating that failure to mobilize TAG is not fully responsible for the growth defect of the dga1Δlro1Δare1Δare2Δ strain in the absence of inositol. Moreover, synthesis of phospholipids, especially PI, is dramatically reduced in the dga1Δlro1Δare1Δare2Δ strain even when it is grown continuously in the presence of inositol. The mutant also utilizes a greater proportion of newly synthesized PI than wild type for the synthesis of inositol-containing sphingolipids, especially in the absence of inositol. Thus, we conclude that storage lipid synthesis actively influences membrane phospholipid metabolism in logarithmically growing cells.

Primary Care Associated With Follow Up Viral Load Testing in Patients Cured of Hepatitis C Infection With Direct Acting Antivirals at a Multidisciplinary Addiction Treatment Program: Insights From a Real-World Setting.

OBJECTIVES: Treatment of hepatitis C virus infection (HCV) with direct acting antiviral therapy is encouraged regardless of substance use status. Patients with substance use disorder are at risk of HCV reinfection after cure. Follow up viral load testing (FUVL) with HCV RNA is recommended. We investigated factors associated with adoption of FUVL in real-world clinical settings. METHODS: Medical records of all patients with SUD who achieved HCV cure with direct acting antivirals at a multidisciplinary addiction treatment program between 2014 and 2019 were reviewed as part of a quality improvement initiative. Demographic and clinical characteristics including SUD treatment, urine toxicology results, and medical service use were collected. Factors associated with FUVL were analyzed and the rate of HCV reinfection was determined. RESULTS: Among 149 patients, 58.4% received FUVL. Receipt of FUVL was associated with engagement in ongoing primary medical care after cure (AOR 4.39, 95% CI [1.67, 11.49]). The HCV reinfection rate among those who received FUVL was 1.95 per 100 person-years of follow up (95% CI [0.64, 5.98]). There was no significant difference in the percentage of negative urine toxicology results before and after cure. CONCLUSIONS: Over half of a cohort of patients with substance use disorder cured of HCV received FUVL. The relationship between FUVL and engagement in primary medical and substance use treatment highlights the importance of integrated systems in providing longitudinal care for patients cured of HCV. Standardized interventions that facilitate FUVL testing and management of infectious complications of SUD in addiction treatment settings are needed.

Interruption of inositol sphingolipid synthesis triggers Stt4p-dependent protein kinase C signaling.

The protein kinase C (PKC)-MAPK signaling cascade is activated and is essential for viability when cells are starved for the phospholipid precursor inositol. In this study, we report that inhibiting inositol-containing sphingolipid metabolism, either by inositol starvation or treatment with agents that block sphingolipid synthesis, triggers PKC signaling independent of sphingoid base accumulation. Under these same growth conditions, a fluorescent biosensor that detects the necessary PKC signaling intermediate, phosphatidylinositol (PI)-4-phosphate (PI4P), is enriched on the plasma membrane. The appearance of the PI4P biosensor on the plasma membrane correlates with PKC activation and requires the PI 4-kinase Stt4p. Like other mutations in the PKC-MAPK pathway, mutants defective in Stt4p and the PI4P 5-kinase Mss4p, which generates phosphatidylinositol 4,5-bisphosphate, exhibit inositol auxotrophy, yet fully derepress INO1, encoding inositol-3-phosphate synthase. These observations suggest that inositol-containing sphingolipid metabolism controls PKC signaling by regulating access of the signaling lipids PI4P and phosphatidylinositol 4,5-bisphosphate to effector proteins on the plasma membrane.

Genome-wide screen for inositol auxotrophy in Saccharomyces cerevisiae implicates lipid metabolism in stress response signaling.

Inositol auxotrophy (Ino(-) phenotype) in budding yeast has classically been associated with misregulation of INO1 and other genes involved in lipid metabolism. To identify all non-essential yeast genes that are necessary for growth in the absence of inositol, we carried out a genome-wide phenotypic screening for deletion mutants exhibiting Ino(-) phenotypes under one or more growth conditions. We report the identification of 419 genes, including 385 genes not previously reported, which exhibit this phenotype when deleted. The identified genes are involved in a wide range of cellular processes, but are particularly enriched in those affecting transcription, protein modification, membrane trafficking, diverse stress responses, and lipid metabolism. Among the Ino(-) mutants involved in stress response, many exhibited phenotypes that are strengthened at elevated temperature and/or when choline is present in the medium. The role of inositol in regulation of lipid metabolism and stress response signaling is discussed.

Pharmacotherapy for metabolic and cellular stress in degenerative retinal diseases.

Retinal photoreceptors continually endure stresses associated with prolonged light exposure and the metabolic demands of dark adaptation. Although healthy photoreceptors are able to withstand these stresses for several decades, the disease-affected retina functions at a reduced capacity and is at an increased risk for dysfunction. To alleviate cellular and metabolic stressors in degenerative retinal diseases, a new class of drugs that modulate the metabolic activity of the retina have been developed. A clinical candidate in this class (emixustat) has been shown to reduce retinal pathology in various animal models of human retinal disease and is currently under clinical study. Here, we describe the pharmacological properties of emixustat, its mechanisms of action, and potential for use in the treatment of specific retinal diseases.

Depletion of phosphatidylcholine in yeast induces shortening and increased saturation of the lipid acyl chains: evidence for regulation of intrinsic membrane curvature in a eukaryote.

To study the consequences of depleting the major membrane phospholipid phosphatidylcholine (PC), exponentially growing cells of a yeast cho2opi3 double deletion mutant were transferred from medium containing choline to choline-free medium. Cell growth did not cease until the PC level had dropped below 2% of total phospholipids after four to five generations. Increasing contents of phosphatidylethanolamine (PE) and phosphatidylinositol made up for the loss of PC. During PC depletion, the remaining PC was subject to acyl chain remodeling with monounsaturated species replacing diunsaturated species, as shown by mass spectrometry. The remodeling of PC did not require turnover by the SPO14-encoded phospholipase D. The changes in the PC species profile were found to reflect an overall shift in the cellular acyl chain composition that exhibited a 40% increase in the ratio of C16 over C18 acyl chains, and a 10% increase in the degree of saturation. The shift was stronger in the phospholipid than in the neutral lipid fraction and strongest in the species profile of PE. The shortening and increased saturation of the PE acyl chains were shown to decrease the nonbilayer propensity of PE. The results point to a regulatory mechanism in yeast that maintains intrinsic membrane curvature in an optimal range.

Emixustat Reduces Metabolic Demand of Dark Activity in the Retina.

Purpose: In the dark, photoreceptor outer segments contain high levels of cyclic guanosine 3'-5' monophosphate (cGMP), which binds to ion channels, holding them open and allowing an influx of cations. Ion pumping activity, which balances cation influx, uses considerable amounts of adenosine triphosphate (ATP) and oxygen. Light reduces cation influx and thereby lowers metabolic demand. Blood vessels are compromised in the diabetic retina and may not be able to meet the higher metabolic demand in darkness. Emixustat is a visual cycle modulator (VCM) that reduces chromophore levels and, therefore, may mimic light conditions. We evaluated the effect of emixustat on oxygen consumption and cation influx in dark conditions. Methods: Cation influx was measured in rats using Mn2+-magnetic resonance imaging (MEMRI). Retinal oxygen profiles were recorded to evaluate oxygen consumption. In the MEMRI protocol, animals were treated with either emixustat or vehicle. In the oxygen protocol, animals were untreated or treated with emixustat. Results: In vehicle-treated animals, cation channel activity increased in the dark. Emixustat treatment reduced cation channel activity; activity was comparable to vehicle-treated controls in light conditions. In vehicle-treated animals, minimum retinal oxygen tension decreased as the retina recovered from a photobleach, indicating that more oxygen was being consumed. Emixustat treatment prevented the decrease in oxygen pressure after photobleach. Conclusions: Emixustat reduced the cation influx and retinal oxygen consumption associated with dark conditions. VCMs are a promising potential treatment for ischemic retinal neovascularization, such as that in diabetic retinopathy.

The emergence of yeast lipidomics.

The emerging field of lipidomics, driven by technological advances in lipid analysis, provides greatly enhanced opportunities to characterize, on a quantitative or semi-quantitative level, the entire spectrum of lipids, or lipidome, in specific cell types. When combined with advances in other high throughput technologies in genomics and proteomics, lipidomics offers the opportunity to analyze the unique roles of specific lipids in complex cellular processes such as signaling and membrane trafficking. The yeast system offers many advantages for such studies, including the relative simplicity of its lipidome as compared to mammalian cells, the relatively high proportion of structural and regulatory genes of lipid metabolism which have been assigned and the excellent tools for molecular genetic analysis that yeast affords. The current state of application of lipidomic approaches in yeast and the advantages and disadvantages of yeast for such studies are discussed in this report.

Upper airway obstruction as the presenting manifestation of leukemia.

The general clinical features of the acute pediatric leukemias are similar. There is a fairly consistent picture of brief symptoms, which include weakness or fatique, bleeding or bruising, and bone or joint tenderness. Acute or subacute fever also is a common symptom. The fever can result from the underlying malignancy, but is more often the result of an infectious complication. We present a toddler, ultimately diagnosed with acute leukemia, who experienced few of the classic features. He presented as a case of febrile upper airway obstruction.

Onsite treatment of HCV infection with direct acting antivirals within an opioid treatment program.

With the advent of the direct acting antivirals (DAA), or all oral HCV treatment regimens, there exists a great opportunity to provide HCV treatment to people who inject drugs (PWID) enrolled in an opioid treatment program (OTP). This retrospective study conducted in the context of routine clinical care explores the outcomes of HCV treatment with DAAs in PWID enrolled in an OTP. Our study showed treatment outcomes among our first 75 patients treated with DAAs were nearly equivalent to patients in the general population. Ninety-eight percent of patients completing treatment obtained a sustained virologic response, with 10 patients lost to follow-up. Ninety-nine percent of patients adhered to HCV treatment. Ongoing drug use occurred in 23% of patients, however this did not alter HCV treatment outcomes. Treating HCV infection with DAAs in PWID onsite in an OTP is feasible.