Inhibition Of Acid Sphingomyelinase Research Articles

Factor of psychopharmacotherapy in in the course of COVID-19 in psychiatric inpatients

The aim of this study is to examine the relationship between the severity and duration criteria of COVID-19 and the psychopharmacotherapy administered to patients in within a psychiatric hospital.Materials and Methods. We analyzed 169 case histories involving completed clinical cases of COVID-19 treatment in a specialized infectious psychiatric department in St. Petersburg, covering the period from May 2020 to January 2021. Correlation, dispersion, and regression analyses were employed to evaluate severe and mild COVID-19 progression indicators, as well as the duration of persistent SARS-CoV-2 viral shedding. We assessed the clinical and laboratory parameters in patients, along with the psychopharmacotherapy administered, including antidepressants, antipsychotics, and acid sphingomyelinase inhibitors (FIASMA-active drugs).Results. Cardiovascular diseases emerged as a predictor of severe COVID-19 when combined with an increasing platelet-to-lymphocyte ratio (PLR), increasing the risk of severe course by over two-fold. The use of any psychotropic agents was associated with a 0.9% increase in the risk of severe course of COVID-19 for each unit increase in the systemic inflammation index PLR, specifically in patients with intellectual disability (ICD-10 codes F70-79), when compared to patients with schizophrenia (ICD-10 codes F20-29). High PLR values and the use of FIASMA-active drugs were associated with prolonged COVID-19 duration, while antidepressant therapy and elevated C-reactive protein levels were associated with a reduced predicted duration of viral shedding in 13.8% of variance. Additional consideration of the nosology of psychiatric disorders in the regression model increased the proportion of explained variance to 22.8%.Conclusion. Consideration should be given to thymoanaleptic therapy for individuals with psychiatric disorders during periods of increased disease incidence leading up to potential SARS-CoV-2 infection, as it may serve as a protective factor against COVID-19. Furthermore, there is no evidence to suggest adverse effects of antipsychotics on the severity and duration of COVID-19. Further research is required to investigate the effects of FIASMA-active psychopharmacological agents within nosologically homogeneous groups.

Fluoxetine and Sertraline Potently Neutralize the Replication of Distinct SARS-CoV-2 Variants.

The pandemic caused by SARS-CoV-2 is still a major health problem. Newly emerging variants and long-COVID-19 represent a challenge for the global health system. In particular, individuals in developing countries with insufficient health care need easily accessible, affordable and effective treatments of COVID-19. Previous studies have demonstrated the efficacy of functional inhibitors of acid sphingomyelinase against infections with various viruses, including early variants of SARS-CoV-2. This work investigated whether the acid sphingomyelinase inhibitors fluoxetine and sertraline, usually used as antidepressant molecules in clinical practice, can inhibit the replication of the former and recently emerged SARS-CoV-2 variants in vitro. Fluoxetine and sertraline potently inhibited the infection with pseudotyped virus-like particles and SARS-CoV-2 variants D614G, alpha, delta, omicron BA.1 and omicron BA.5. These results highlight fluoxetine and sertraline as priority candidates for large-scale phase 3 clinical trials at different stages of SARS-CoV-2 infections, either alone or in combination with other medications.

The acid sphingomyelinase inhibitor imipramine enhances the release of UV photoproduct-containing DNA in small extracellular vesicles in UVB-irradiated human skin.

Nucleic acids, lipids, and other cell components can be found within different types of extracellular vesicles (EVs), which include apoptotic bodies (ABs), large extracellular vesicles (LEVs), and small extracellular vesicles (SEVs). Release of LEVs from cells can be reduced by genetic or pharmacological inhibition of the enzyme acid sphinogomyelinase (aSMase), and indeed several studies have demonstrated a role for the clinically approved aSMase inhibitor imipramine in blocking LEV release, including in response to UVB exposure. Given that exposure of keratinocytes to UVB radiation results in the generation of UVR photoproducts in DNA that can subsequently be found in association with ABs and SEVs, we examined how imipramine impacts the release of extracellular DNA containing UVR photoproducts at an early time point after UVR exposure. Using several different model systems, including cultured keratinocytes invitro, discarded human surgical skin exvivo, and skin biopsies obtained from treated human subjects, these pilot studies suggest that imipramine treatment stimulates the release of CPD-containing, SEV-associated DNA. These surprising findings indicate that LEV and SEV generation pathways could be linked in UVB-irradiated cells and that imipramine may exacerbate the systemic effects of extracellular UVR-damaged DNA throughout the body.

Desipramine ameliorates fine particulate matter-induced hepatic insulin resistance by modulating the ceramide metabolism in mice

Recent research has highlighted a correlation between exposure to ambient fine particulate matter (PM2.5) and the development of systemic insulin resistance (IR) along with an elevated risk of diabetes. Ceramide has emerged as one of the pathogenic mechanisms contributing to IR. The inhibition of acid sphingomyelinase (ASMase) activity by desipramine (DES) has been shown to effectively reduce ceramide levels. In the present study, 24 female C57BL/6 N mice were randomized into one of the four groups: the filtered air exposure (FA) group, the concentrated PM2.5 exposure (PM) group, the concentrated PM2.5 treated with low-dose DES (DL) group, and the concentrated PM2.5 treated with high-dose DES (DH) group. The PM, DL and DH groups were exposed to PM2.5 for an 8-week period within a whole-body exposure system. The study encompassed extensive examinations of glucose homeostasis, liver lipid profile, ceramide pathway, and insulin signaling pathway. Our results demonstrated that PM2.5 exposure caused impaired glucose tolerance, elevated ceramide levels, increased phosphorylation PP2A, reduced Akt phosphorylation, and hindered GLUT2 expression. Remarkably, DES administration mitigated PM2.5-induced IR by effectively lowering ceramide levels. In conclusion, the reduction of ceramide levels by DES may be a promising therapeutic strategy for coping PM2.5-induced IR.

Amitriptyline inhibits bronchoconstriction and directly promotes dilatation of the airways

IntroductionThe standard therapy for bronchial asthma consists of combinations of acute (short-acting ß2-sympathomimetics) and, depending on the severity of disease, additional long-term treatment (including inhaled glucocorticoids, long-acting ß2-sympathomimetics, anticholinergics, anti-IL-4R antibodies). The antidepressant amitriptyline has been identified as a relevant down-regulator of immunological TH2-phenotype in asthma, acting—at least partially—through inhibition of acid sphingomyelinase (ASM), an enzyme involved in sphingolipid metabolism. Here, we investigated the non-immunological role of amitriptyline on acute bronchoconstriction, a main feature of airway hyperresponsiveness in asthmatic disease.MethodsAfter stimulation of precision cut lung slices (PCLS) from mice (wildtype and ASM-knockout), rats, guinea pigs and human lungs with mediators of bronchoconstriction (endogenous and exogenous acetylcholine, methacholine, serotonin, endothelin, histamine, thromboxane-receptor agonist U46619 and leukotriene LTD4, airway area was monitored in the absence of or with rising concentrations of amitriptyline. Airway dilatation was also investigated in rat PCLS by prior contraction induced by methacholine. As bronchodilators for maximal relaxation, we used IBMX (PDE inhibitor) and salbutamol (ß2-adrenergic agonist) and compared these effects with the impact of amitriptyline treatment. Isolated perfused lungs (IPL) of wildtype mice were treated with amitriptyline, administered via the vascular system (perfusate) or intratracheally as an inhalation. To this end, amitriptyline was nebulized via pariboy in-vivo and mice were ventilated with the flexiVent setup immediately after inhalation of amitriptyline with monitoring of lung function.ResultsOur results show amitriptyline to be a potential inhibitor of bronchoconstriction, induced by exogenous or endogenous (EFS) acetylcholine, serotonin and histamine, in PCLS from various species. The effects of endothelin, thromboxane and leukotrienes could not be blocked. In acute bronchoconstriction, amitriptyline seems to act ASM-independent, because ASM-deficiency (Smdp1−/−) did not change the effect of acetylcholine on airway contraction. Systemic as well as inhaled amitriptyline ameliorated the resistance of IPL after acetylcholine provocation. With the flexiVent setup, we demonstrated that the acetylcholine-induced rise in central and tissue resistance was much more marked in untreated animals than in amitriptyline-treated ones. Additionally, we provide clear evidence that amitriptyline dilatates pre-contracted airways as effectively as a combination of typical bronchodilators such as IBMX and salbutamol.ConclusionAmitriptyline is a drug of high potential, which inhibits acute bronchoconstriction and induces bronchodilatation in pre-contracted airways. It could be one of the first therapeutic agents in asthmatic disease to have powerful effects on the TH2-allergic phenotype and on acute airway hyperresponsiveness with bronchoconstriction, especially when inhaled.

Inhibition of acid sphingomyelinase reduces reactive astrocyte secretion of mitotoxic extracellular vesicles and improves Alzheimer’s disease pathology in the 5xFAD mouse

In Alzheimer’s disease (AD), reactive astrocytes produce extracellular vesicles (EVs) that affect mitochondria in neurons. Here, we show that Aβ-induced generation of the sphingolipid ceramide by acid sphingomyelinase (A-SMase) triggered proinflammatory cytokine (C1q, TNF-α, IL-1α) release by microglia, which induced the reactive astrocytes phenotype and secretion of EVs enriched with ceramide. These EVs impeded the capacity of neurons to respond to energy demand. Inhibition of A-SMase with Arc39 and Imipramine reduced the secretion of cytokines from microglia, prompting us to test the effect of Imipramine on EV secretion and AD pathology in the 5xFAD mouse model. Brain derived-EVs from 5xFAD mice treated with Imipramine contained reduced levels of the astrocytic marker GFAP, ceramide, and Aβ and did not impair mitochondrial respiration when compared to EVs derived from untreated 5xFAD brain. Consistently, Imipramine-treated 5xFAD mice showed reduced AD pathology. Our study identifies A-SMase inhibitors as potential AD therapy by preventing cyotokine-elicited secretion of mitotoxic EVs from astrocytes.

1638-P: Oxidized Lipids Cause Ceramide Accumulation and Insulin Resistance in Skeletal Muscle

Accumulation of muscle lipids promotes insulin resistance and type 2 diabetes (T2D). Ceramides are important muscle lipids that decrease insulin sensitivity and it was previously shown that accumulation of ceramides in the sarcolemma negatively impacts insulin sensitivity in humans. The mechanisms explaining accumulation of lipids in specific compartments in skeletal muscle are unknown, but one possibility is through circulating oxidized lipids. POVPC, a major circulating oxidized phospholipid, was exposed to rat myotubes (1-50 μM) for 4h and the total cellular ceramide levels in myotubes measured by LC-MS/MS. Total ceramide content increased dose dependently at POVPC doses in the physiological range (5 μM, p <0.05). To determine the mechanism of POVPC induced ceramide accumulation, ceramide was measured in myotubes after treatment with POVPC (25 μM) in the presence of inhibitors of neutral and acid sphingomyelinase (GW4869 and ARC39), ceramide synthase (fumonisin B1) and serine palmitoyltransferase (myriocin). The individually administered inhibitors in the presence of POVPC each showed a decrease (41-55%) in ceramide accumulation. When all of inhibitors were administered together along with POVPC, an almost complete inhibition of ceramide accumulation (95%) was observed indicating that the sphingomyelinase, de novo, and salvage pathways of ceramide synthesis are activated by POVPC. The role of oxidized lipids on insulin sensitivity was examined after treatment of rat myotubes with 1-25 μM POVPC. Increasing doses of POVPC at doses as low as 1 μM significantly decreased insulin sensitivity in vitro (p <0.05). These results reveal circulating oxidized lipids promote ceramide accumulation and insulin resistance in muscle cells and may help explain variability in total and localized muscle ceramide levels between individuals. These data also suggest that therapies designed to lower circulating oxidized lipids could be beneficial for the treatment and prevention of T2D. Disclosure K.Zemski berry: None. B.C.Bergman: Research Support; Eli Lilly and Company. Funding National Institutes of Health (P30DK048520); University of Colorado (25N0350)

Novel Isolation Method Reveals Sex-Specific Composition and Neurotoxicity of Small Extracellular Vesicles in a Mouse Model of Alzheimer's Disease.

We developed a new method to isolate small extracellular vesicles (sEVs) from male and female wild-type and 5xFAD mouse brains to investigate the sex-specific functions of sEVs in Alzheimer's disease (AD). A mass spectrometric analysis revealed that sEVs contained proteins critical for EV formation and Aβ. ExoView analysis showed that female mice contained more GFAP and Aβ-labeled sEVs, suggesting that a larger proportion of sEVs from the female brain is derived from astrocytes and/or more likely to bind to Aβ. Moreover, sEVs from female brains had more acid sphingomyelinase (ASM) and ceramide, an enzyme and its sphingolipid product important for EV formation and Aβ binding to EVs, respectively. We confirmed the function of ASM in EV formation and Aβ binding using co-labeling and proximity ligation assays, showing that ASM inhibitors prevented complex formation between Aβ and ceramide in primary cultured astrocytes. Finally, our study demonstrated that sEVs from female 5xFAD mice were more neurotoxic than those from males, as determined by impaired mitochondrial function (Seahorse assays) and LDH cytotoxicity assays. Our study suggests that sex-specific sEVs are functionally distinct markers for AD and that ASM is a potential target for AD therapy.

Acid sphingomyelinase expression is associated with survival in resectable pancreatic ductal adenocarcinoma

Pancreatic adenocarcinoma (PDAC) is one of the most common cancers worldwide. Unfortunately, the prognosis of PDAC is rather poor, and for instance, in the USA, over 47,000 people die because of pancreatic cancer annually. Here, we demonstrate that high expression of acid sphingomyelinase in PDAC strongly correlates with long-term survival of patients, as revealed by the analysis of two independent data sources. The positive effects of acid sphingomyelinase expression on long-term survival of PDAC patients were independent of patient demographics as well as tumor grade, lymph node involvement, perineural invasion, tumor stage, lymphovascular invasion, and adjuvant therapy. We also demonstrate that genetic deficiency or pharmacological inhibition of the acid sphingomyelinase promotes tumor growth in an orthotopic mouse model of PDAC. This is mirrored by a poorer pathologic response, as defined by the College of American Pathologists (CAP) score for pancreatic cancer, to neoadjuvant therapy of patients co-treated with functional inhibitors of the acid sphingomyelinase, in particular tricyclic antidepressants and selective serotonin reuptake inhibitors, in a retrospective analysis. Our data indicate expression of the acid sphingomyelinase in PDAC as a prognostic marker for tumor progression. They further suggest that the use of functional inhibitors of the acid sphingomyelinase, at least of tricyclic antidepressants and selective serotonin reuptake inhibitors in patients with PDAC, is contra-indicated. Finally, our data also suggest a potential novel treatment of PDAC patients with recombinant acid sphingomyelinase.Key messagesPancreatic ductal adenocarcinoma (PDAC) is a common tumor with poor prognosis.Expression of acid sphingomyelinase (ASM) determines outcome of PDAC.Genetic deficiency or pharmacologic inhibition of ASM promotes tumor growth in a mouse model.Inhibition of ASM during neoadjuvant treatment for PDAC correlates with worse pathology.ASM expression is a prognostic marker and potential target in PDAC.

The Presence of Periodontitis Exacerbates Non-Alcoholic Fatty Liver Disease via Sphingolipid Metabolism-Associated Insulin Resistance and Hepatic Inflammation in Mice with Metabolic Syndrome.

Clinical studies have shown that periodontitis is associated with non-alcoholic fatty liver disease (NAFLD). However, it remains unclear if periodontitis contributes to the progression of NAFLD. In this study, we generated a mouse model with high-fat diet (HFD)-induced metabolic syndrome (MetS) and NAFLD and oral P. gingivalis inoculation-induced periodontitis. Results showed that the presence of periodontitis increased insulin resistance and hepatic inflammation and exacerbated the progression of NAFLD. To determine the role of sphingolipid metabolism in the association between NAFLD and periodontitis, we also treated mice with imipramine, an inhibitor of acid sphingomyelinase (ASMase), and demonstrated that imipramine treatment significantly alleviated insulin resistance and hepatic inflammation, and improved NAFLD. Studies performed in vitro showed that lipopolysaccharide (LPS) and palmitic acid (PA), a major saturated fatty acid associated with MetS and NAFLD, synergistically increased the production of ceramide, a bioactive sphingolipid involved in NAFLD progression in macrophages but imipramine effectively reversed the ceramide production stimulated by LPS and PA. Taken together, this study showed for the first time that the presence of periodontitis contributed to the progression of NAFLD, likely due to alterations in sphingolipid metabolism that led to exacerbated insulin resistance and hepatic inflammation. This study also showed that targeting ASMase with imipramine improves NAFLD by reducing insulin resistance and hepatic inflammation.

Mechanisms of pulmonary microvascular endothelial cells barrier dysfunction induced by LPS: The roles of ceramides and the Txnip/NLRP3 inflammasome.

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) are characterized by pulmonary microvascular endothelial cells (PMVECs) barrier dysfunction and proinflammatory cytokine influx into lung tissue, resulting in pulmonary oedema. Ceramide overproduction is an important mediator of pulmonary hyperinflammation and pulmonary oedema in Acute lung injury (ALI). Ceramides induce NLRP3 inflammasome activation are essential for the hyperinflammatory response. However, the roles and specific mechanisms of ceramide-induced NLRP3 inflammasome activation, proinflammatory cytokine manufacturing and PMVECs barrier dysfunction in ALI are unclear. Herein, pretreatment with the acid sphingomyelinase (ASMase) inhibitor imipramine (but not a neutral sphingomyelinase (NSMase) inhibitor or de novo pathway inhibitor) significantly inhibited ceramide early production in rats with lipopolysaccharide (LPS)-induced ALI; Furthermore, the Txnip/NLRP3 inflammasome activation, proinflammatory cytokine release, increased PMVECs permeability and lung injury were significantly decreased. Verapamil, a Txnip inhibitor, substantially inhibited Txnip/NLRP3 inflammasome activation, proinflammatory cytokine release, increased PMVECs permeability and lung injury in rats with C8-ceramide-induced ALI. In vitro, short hairpin RNA-mediated Txnip silencing significantly inhibited C8-ceramide-induced Txnip/NLRP3 inflammasome activation in NR8383 alveolar macrophages (AMs) and early secretion of the proinflammatory cytokines IL-1β (4-12h) as well as IL-6 and TNF-α at subsequent times (later than 12h). However, C8-ceramide significantly increased the early secretion (within 8h) of the proinflammatory cytokines IL-1β, IL-6 and TNF-α in a co-culture model of NR8383 AMs and PMVECs, and Txnip silencing of NR8383 AMs inhibited the secretion of pro-inflammatory cytokines and reduced cytoskeletal rearrangements, intercellular connection breakage and hyperpermeability in PMVECs. Overall, our results suggest that in LPS-induced ALI, ceramide-mediated Txnip/NLRP3 inflammasome activation in NR8383 AMs leads to early IL-1β release, subsequently inducing PMVECs injury and release of the proinflammatory cytokines IL-6 and TNF-α, ultimately leading to PMVECs barrier dysfunction and ALI.

Desipramine enhances the stability of atherosclerotic plaque in rabbits monitored with molecular imaging.

Acid sphingomyelinase (ASM) promotes atherogenesis and acute cardiovascular events. We previously demonstrated ASM inhibitor desipramine attenuated oxidized-LDL-induced macrophage apoptosis in vitro. Here, we aim to determine whether ASM-mediated apoptosis in plaque improves stability in vivo. In this study, rabbits with abdominal aorta balloon injury and a 12-week high-cholesterol diet (HCD) were used to simulate an atherosclerotic plaque model. Atherosclerotic rabbits received oral administration of saline (Control group), atorvastatin (Ator group), or desipramine (DES group). ASM activity and ceramide level were measured by ultra-performance liquid chromatography (UPLC). Plaque morphology was assessed by histochemistry and immunohistochemistry. Apoptosis was evaluated by SPECT/CT imaging of 99mTc-duramycin uptake and TUNEL. We found that increasing ASM activity and ceramide level in atherosclerotic rabbits was abated by additional atorvastatin and desipramine treatment. Meanwhile, the DES and Ator groups were similar in plaque stability, with smaller plaque size, areas of macrophages, higher smooth muscle cell content, and decreased apoptosis and matrix metalloproteinase (MMP) activities relative to the Control group. 99mTc-duramycin uptake of rabbit aorta was significantly higher in Control than in the Normal group, while it was reduced by desipramine and atorvastatin administration. Moreover, the uptake of 99mTc-duramycin positively correlated with apoptotic cell number, macrophage infiltration, and plaque instability. The present study demonstrated that desipramine exerted plaque-stabilizing effects partially by suppressing apoptosis and MMP activity in a rabbit model. And 99mTc-duramycin SPECT/CT imaging allowed noninvasively monitoring of atherosclerotic disease and evaluation of anti-atherosclerotic therapy.

Acid sphingomyelinase (ASM) and COVID‐19: A review of the potential use of ASM inhibitors against SARS‐CoV‐2

In the last 2 years, different pharmacological agents have been indicated as potential inhibitors of SARS-CoV-2 in vitro. Specifically, drugs termed as functional inhibitors of acid sphingomyelinase (FIASMAs) have proved to inhibit the SARS-CoV-2 replication using different types of cells. Those therapeutic agents share several chemical structure characteristics and some well-known representatives are fluoxetine, escitalopram, fluvoxamine, and others. Most of theFIASMAs are primarily used as effective therapeutic agents to treat different pathologies, therefore, they are natural drug candidates for repositioning strategy. In this review, we summarize the two main proposed mechanisms mediating acid sphingomyelinase(ASM) inhibition and how they can explain the inhibition of SARS-CoV-2 replication by FIASMAs. The first mechanism implies a disruption in the lysosomal pH fall as the endosome-lysosome moves toward the interior of the cell. In fact, changes in cholesterol levels in endosome-lysosome membranes, which are associated with ASM inhibition is thought to be mediated by lysosomal proton pump (ATP-ase) inactivation. The second mechanism involves the formation of an extracellular ceramide-rich domain, which is blocked by FIASMAs. The ceramide-rich domains are believed to facilitate the SARS-CoV-2entrance into the host cells.

Macrophage-derived exosomes mediate glomerular endothelial cell dysfunction in sepsis-associated acute kidney injury

BackgroundSepsis-associated AKI has been shown to be related to sepsis mortality. Macrophage activation and endothelial cell damage are involved in the progression of sepsis-associated AKI, but the specific mechanisms are still unclear.MethodsIn vitro experiments, exosomes extracted from lipopolysaccharide (LPS) -stimulated macrophages were co-incubated with rat glomerular endothelial cells (RGECs) and then detected the injury markers of RGECs. Acid sphingomyelinase (ASM) inhibitor amitriptyline were used to investigate the role of ASM. In vivo experiment, exosomes produced by LPS-stimulated macrophages were injected into mice through tail vein to further explore the role of macrophage-derived exosomes. Moreover, ASM knockout mice were used to verify the mechanism.ResultIn vitro, the secretion of macrophage exosomes increased upon the stimulation with LPS. Notably, macrophage-derived exosomes can cause glomerular endothelial cell dysfunction. In vivo, macrophage infiltration and exosome secretion in glomeruli of the LPS-induced AKI group increased. The exosomes produced by LPS-stimulated macrophages were injected into mice, which also led to the injury of renal endothelial cells. In addition, in the LPS-induced AKI mouse model, compared with wild-type mice, the secretion of exosomes in glomeruli of ASM gene knockout mice and the injury of endothelial cells were reduced.ConclusionOur study shows that ASM regulates the secretion of macrophage exosomes, leading to endothelial cell injury, which may be a therapeutic target in sepsis-associated AKI.

Antidepressant Use and Its Association with 28-Day Mortality in Inpatients with SARS-CoV-2: Support for the FIASMA Model against COVID-19

Introduction To reduce Coronavirus Disease 2019 (COVID-19)-related mortality and morbidity, widely available oral COVID-19 treatments are urgently needed. Certain antidepressants, such as fluvoxamine or fluoxetine, may be beneficial against COVID-19. Objectives The main objective was two-fold: (i) to test the hypothesis that the prevalence of antidepressant use in patients hospitalized with COVID-19 would be lower than in patients with similar characteristics hospitalized without COVID-19, and (ii) to examine, among patients hospitalized with COVID-19, whether antidepressant use is associated with reduced 28-day mortality. Our secondary aim was to examine whether this potential association could only concern specific antidepressant classes or molecules, is dose-dependent, and/or only observed beyond a certain dose threshold. Methods We included 388,945 adult inpatients who tested positive for SARS-CoV-2 at 36 AP–HP (Assistance Publique–Hôpitaux de Paris) hospitals from 2 May 2020 to 2 November 2021. We compared the prevalence of antidepressant use at admission in a 1:1 ratio matched analytic sample with and without COVID-19 (N = 82,586), and assessed its association with 28-day all-cause mortality in a 1:1 ratio matched analytic sample of COVID-19 inpatients with and without antidepressant use at admission (N = 1482) (Figure 1). Results Antidepressant use was significantly less prevalent in inpatients with COVID-19 than in a matched control group of inpatients without COVID-19 (1.9% versus 4.8%; Odds Ratio (OR) = 0.38; 95%CI = 0.35–0.41, p < 0.001) (Figure 2). Antidepressant use was significantly associated with reduced 28-day mortality among COVID-19 inpatients (12.8% versus 21.2%; OR = 0.55; 95%CI = 0.41–0.72, p < 0.001), particularly at daily doses of at least 40 mg fluoxetine equivalents (Figure 3). Antidepressants with high FIASMA (Functional Inhibitors of Acid Sphingomyelinase) activity seem to drive both associations. Image: Image 2: Image 3: Conclusions Antidepressant use is associated with a reduced likelihood of hospitalization in patients infected with SARS-CoV-2 and with a reduced risk of death in patients hospitalized with COVID-19. These associations were stronger for molecules with high FIASMA activity. These findings posit that prospective interventional studies of antidepressants with the highest FIASMA activity may be appropriate to help identify variant-agnostic, affordable, and scalable interventions for outpatient and inpatient therapy of COVID-19. Disclosure of Interest None Declared

Discovery of Novel N-Hydroxy-1,2,4-oxadiazole-5-formamides as ASM Direct Inhibitors for the Treatment of Atherosclerosis.

Acid sphingomyelinase (ASM), which regulates sphingolipid metabolism and lipid signaling, has been considered as a new potential target for the treatment of atherosclerosis. In this study, a series of benzene-heterocyclic-based ASM inhibitors were rationally designed, synthesized, and screened for the first time. As a result, some compounds showed favorable inhibitory activity against recombinant human ASM. The detailed SARs are also discussed. Compound 4i revealed good pharmacokinetic data and in vivo inhibitory activity against ASM by reducing the level of ceramide in mice plasma and liver. Pharmacodynamic studies confirmed that 4i could lessen lipid plaques in the aortic arch and aorta and reduce plasma ceramide concentration and Ox-LDL levels. Moreover, 4i was found to significantly decrease LPS-induced and Ox-LDL-induced cell inflammation by regulating the levels of ceramide and sphingomyelin. Overall, this study preliminarily demonstrates that ASM may be an effective target against atherosclerosis for the first time.

Sphingomyelin metabolism underlies Ras excitability for efficient cell migration and chemotaxis.

In eukaryotic motile cells, the active Ras (Ras-GTP)-enriched domain is generated in an asymmetric manner on the cell membrane through the excitable dynamics of an intracellular signaling network. This asymmetric Ras signaling regulates pseudopod formation for both spontaneous random migration and chemoattractant-induced directional migration. While membrane lipids, such as sphingomyelin and phosphatidylserine, contribute to Ras signaling in various cell types, whether they are involved in the Ras excitability for cell motility is unknown. Here we report that functional Ras excitability requires the normal metabolism of sphingomyelin for efficient cell motility and chemotaxis. The pharmacological blockade of sphingomyelin metabolism by an acid-sphingomyelinase inhibitor, fendiline, and other inhibitors suppressed the excitable generation of the stable Ras-GTP-enriched domain. The suppressed excitability failed to invoke enough basal motility to achieve directed migration under shallow chemoattractant gradients. The fendiline-induced defects in Ras excitability, motility and stimulation-elicited directionality were due to an accumulation of sphingomyelin on the membrane, which could be recovered by exogenous sphingomyelinase or phosphatidylserine without changing the expression of Ras. These results indicate a novel regulatory mechanism of the excitable system by membrane lipids, in which sphingomyelin metabolism provides a membrane environment to ensure Ras excitation for efficient cellular motility and chemotaxis.Key words: cell polarity, cell migration, Ras, excitability, sphingomyelin.

Acid sphingomyelinase inhibition improves motor behavioral deficits and neuronal loss in an amyotrophic lateral sclerosis mouse model

Amyotrophic lateral sclerosis (ALS) is an incurable neurodegenerative disease characterized by the degeneration of motor neurons in the spinal cord. Main symptoms are manifested as weakness, muscle loss, and muscle atrophy. Some studies have reported that alterations in sphingolipid metabolism may be intimately related to neurodegenerative diseases, including ALS. Acid sphingomyelinase (ASM), a sphingolipid-metabolizing enzyme, is considered an important mediator of neurodegenerative diseases. Herein, we show that ASM activity increases in samples from patients with ALS and in a mouse model. Moreover, genetic inhibition of ASM improves motor function impairment and spinal neuronal loss in an ALS mouse model. Therefore, these results suggest the role of ASM as a potentially effective target and ASM inhibition may be a possible therapeutic approach for ALS. [BMB Reports 2022; 55(12): 621-626].

Acid Sphingomyelinase Inhibitor, Imipramine, Reduces Hippocampal Neuronal Death after Traumatic Brain Injury

Traumatic brain injury (TBI) broadly degrades the normal function of the brain after a bump, blow, or jolt to the head. TBI leads to the aggravation of pre-existing brain dysfunction and promotes neurotoxic cascades that involve processes such as oxidative stress, loss of dendritic arborization, and zinc accumulation. Acid sphingomyelinase (ASMase) is an enzyme that hydrolyzes sphingomyelin to ceramide in cells. Under normal conditions, ceramide plays an important role in various physiological functions, such as differentiation and apoptosis. However, under pathological conditions, excessive ceramide production is toxic and activates the neuronal-death pathway. Therefore, we hypothesized that the inhibition of ASMase activity by imipramine would reduce ceramide formation and thus prevent TBI-induced neuronal death. To test our hypothesis, an ASMase inhibitor, imipramine (10 mg/kg, i.p.), was administrated to rats immediately after TBI. Based on the results of this study, we confirmed that imipramine significantly reduced ceramide formation, dendritic loss, oxidative stress, and neuronal death in the TBI-imipramine group compared with the TBI-vehicle group. Additionally, we validated that imipramine prevented TBI-induced cognitive dysfunction and the modified neurological severity score. Consequently, we suggest that ASMase inhibition may be a promising therapeutic strategy to reduce hippocampal neuronal death after TBI.

In silico analysis of the antidepressant fluoxetine and similar drugs as inhibitors of the human protein acid sphingomyelinase: a related SARS-CoV-2 inhibition pathway

Acid Sphingomyelinase (ASM) is a human phosphodiesterase that catalyzes the metabolism of sphingomyelin (SM) to ceramide and phosphocholine. ASM is involved in the plasma membrane cell repair and is associated with the lysosomal inner lipid membrane by nonbonding interactions. The disruption of those interaction would result in ASM release into the lysosomal lumen and consequent degradation of its structure. Furthermore, SARS-CoV-2 infection has been linked with ASM activation and with a ceramide domain formation in the outer leaflet of the plasma membrane that is thought to be crucial for the viral particles recognition by the host cells. In this study, we have explored in silico the behavior of fluoxetine and related drugs as potential inhibitors of ASM. Theoretically, these drugs would be able to overpass lysosomal membrane and reach the interactions that sustain ASM structure, breaking them and inhibiting the ASM. The analyses of docking data indicated that fluoxetine allocated mainly in the N-terminal saposin domain via nonbonding interactions, mostly of hydrophobic nature. Similar results were obtained for venlafaxine, citalopram, atomoxetine, nisoxetine and fluoxetine’s main metabolite norfluoxetine. In conclusion, it was observed that the saposin allocation may be a good indicative of the drugs inhibition mechanism, once this domain is responsible for the binding of ASM to lysosomal membrane and some of those drugs have previously been reported to inhibit the phosphodiesterase by releasing its structure in the lysosomal lumen. Our MD data also provides some insight about natural ligand C18 sphingomyelin conformations on saposin. Communicated by Ramaswamy H. Sarma