In vitro inhibition of the replication of human immunodeficiency virus type 1 by beta-mercaptoethylamine (cysteamine)

Cysteamine-mediated blockade of the glycine cleavage system modulates epithelial cell inflammatory and innate immune responses to viral infection

Transient blockade of glycine decarboxylase (GLDC) can restrict de novo pyrimidine synthesis, which is a well-described strategy for enhancing the host interferon response to viral infection and a target pathway for some licenced anti-inflammatory therapies. The aminothiol, cysteamine, is produced endogenously during the metabolism of coenzyme A, and is currently being investigated in a clinical trial as an intervention in community acquired pneumonia resulting from viral (influenza and SARS-CoV-2) and bacterial respiratory infection. Cysteamine is known to inhibit both bacterial and the eukaryotic host glycine cleavage systems via competitive inhibition of GLDC at concentrations, lower than those required for direct antimicrobial or antiviral activity. Here, we demonstrate for the first time that therapeutically achievable concentrations of cysteamine can inhibit glycine utilisation by epithelial cells and improve cell-mediated responses to infection with respiratory viruses, including human coronavirus 229E and Influenza A. Cysteamine reduces interleukin-6 (IL-6) and increases the interferon-λ (IFN-λ) response to viral challenge and in response to liposomal polyinosinic:polycytidylic acid (poly I:C) simulant of RNA viral infection.

In vitro activity of cysteamine against SARS-CoV-2 variants

Global COVID-19 pandemic is caused by infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Continuous emergence of new variants and their rapid spread are jeopardizing vaccine countermeasures to a significant extent. While currently available vaccines are effective at preventing illness associated with SARS-CoV-2 infection, these have been shown to be less effective at preventing breakthrough infection and transmission from a vaccinated individual to others. Here we demonstrate broad antiviral activity of cysteamine HCl in vitro against major emergent infectious variants of SARS-CoV-2 in a highly permissible Vero cell line. Cysteamine HCl inhibited infection of wild type, alpha, beta, gamma, delta, lambda, and omicron variants effectively. Cysteamine is a very well-tolerated US FDA-approved drug used chronically as a topical ophthalmic solution to treat ocular cystinosis in patients who receive it hourly or QID lifelong at concentrations 6 times higher than that required to inhibit SARS CoV-2 in tissue culture. Application of cysteamine as a topical nasal treatment can potentially1) mitigate existing infection 2) prevent infection in exposed individuals, and 3) limit the contagion in vulnerable populations.

Cysteamine with In Vitro Antiviral Activity and Immunomodulatory Effects Has the Potential to Be a Repurposing Drug Candidate for COVID-19 Therapy

The ongoing pandemic of coronavirus disease-2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), needs better treatment options both at antiviral and anti-inflammatory levels. It has been demonstrated that the aminothiol cysteamine, an already human applied drug, and its disulfide product of oxidation, cystamine, have anti-infective properties targeting viruses, bacteria, and parasites. To determine whether these compounds exert antiviral effects against SARS-CoV-2, we used different in vitro viral infected cell-based assays. Moreover, since cysteamine has also immune-modulatory activity, we investigated its ability to modulate SARS-CoV-2-specific immune response in vitro in blood samples from COVID-19 patients. We found that cysteamine and cystamine decreased SARS-CoV-2-induced cytopathic effects (CPE) in Vero E6 cells. Interestingly, the antiviral action was independent of the treatment time respect to SARS-CoV-2 infection. Moreover, cysteamine and cystamine significantly decreased viral production in Vero E6 and Calu-3 cells. Finally, cysteamine and cystamine have an anti-inflammatory effect, as they significantly decrease the SARS-CoV-2 specific IFN-γ production in vitro in blood samples from COVID-19 patients. Overall, our findings suggest that cysteamine and cystamine exert direct antiviral actions against SARS-CoV-2 and have in vitro immunomodulatory effects, thus providing a rational to test these compounds as a novel therapy for COVID-19.

What role for cysteamine in the defence against infection?

The aminothiol cysteamine has many potential therapeutic applications and is also an endogenous molecule, produced in the body via the activity of pantetheinase enzymes such as vanin-1. This simple small molecule is highly reactive in biological settings and much is yet unknown about its endogenous role in innate immunity to infection, including the impact of cysteamine on bacterial pathogens. We discuss the literature surrounding its biochemistry and challenges to its development as well as the multiple beneficial properties which have been uncovered that support research into its development as novel antimicrobial therapy.

Cysteamine mitigates torsion/detorsion-induced reperfusion injury via inhibition of apoptosis, oxidative stress and inflammatory responses in experimental rat model

Oxidative stress, inflammation and apoptosis are major pathways in pathophysiology of testicular torsion/detorsion (TTDT) reperfusion injury. This study evaluated the antioxidant, anti-inflammatory and anti-apoptotic role of cysteamine in TTDT-induced injury. Male Wistar rats (n = 32) were grouped into four (n = 8): sham, ischaemia-reperfusion injury (IRI), cysteamine (100 mg/kg and 200 mg/kg) for in vivo study. Samples were taken for biomolecular and histological evaluation 48 hr after detorsion. Tissue SOD, GPx, GSH, GST activity, total thiol, H₂ O₂ and MDA were assessed. Serum levels of NO, MPO, TNF-alpha and IL-6 and sperm motility, count and viability were assessed. Caspase-3 and bax were evaluated by immunohistochemistry. Significant difference was set as p < .05. Significant increase in H₂ O_2, MDA and nitrite but reduction in SOD, GPx, GSH, GST and total thiol in the testicular tissue of IRI rats was reversed by cysteamine. Serum MPO and TNF-α were significantly elevated in RI, while treated-RI rats showed decrease (p < .05) in tissue level of the inflammation markers. Reduced sperm motility in RI was significantly reversed by cysteamine. Increased tissue expression of bax and caspase-3 was reversed by cysteamine. Cysteamine protected the testis against reperfusion injury through anti-inflammatory, antioxidant effects and inhibition of apoptosis in rats.

Intracellular Redox-Modulated Pathways as Targets for Effective Approaches in the Treatment of Viral Infection

Host-directed therapy using drugs that target cellular pathways required for virus lifecycle or its clearance might represent an effective approach for treating infectious diseases. Changes in redox homeostasis, including intracellular glutathione (GSH) depletion, are one of the key events that favor virus replication and contribute to the pathogenesis of virus-induced disease. Redox homeostasis has an important role in maintaining an appropriate Th1/Th2 balance, which is necessary to mount an effective immune response against viral infection and to avoid excessive inflammatory responses. It is known that excessive production of reactive oxygen species (ROS) induced by viral infection activates nuclear factor (NF)-kB, which orchestrates the expression of viral and host genes involved in the viral replication and inflammatory response. Moreover, redox-regulated protein disulfide isomerase (PDI) chaperones have an essential role in catalyzing formation of disulfide bonds in viral proteins. This review aims at describing the role of GSH in modulating redox sensitive pathways, in particular that mediated by NF-kB, and PDI activity. The second part of the review discusses the effectiveness of GSH-boosting molecules as broad-spectrum antivirals acting in a multifaceted way that includes the modulation of immune and inflammatory responses.

Oral cysteamine as an adjunct treatment in cystic fibrosis pulmonary exacerbations: An exploratory randomized clinical trial

BACKGROUND

Emerging data suggests a possible role for cysteamine as an adjunct treatment for pulmonary exacerbations of cystic fibrosis (CF) that continue to be a major clinical challenge. There are no studies investigating the use of cysteamine in pulmonary exacerbations of CF. This exploratory randomized clinical trial was conducted to answer the question: In future pivotal trials of cysteamine as an adjunct treatment in pulmonary exacerbations of CF, which candidate cysteamine dosing regimens should be tested and which are the most appropriate, clinically meaningful outcome measures to employ as endpoints?

METHODS AND FINDINGS

Multicentre double-blind randomized clinical trial. Adults experiencing a pulmonary exacerbation of CF being treated with standard care that included aminoglycoside therapy were randomized equally to a concomitant 14-day course of placebo, or one of 5 dosing regimens of cysteamine. Outcomes were recorded on days 0, 7, 14 and 21 and included sputum bacterial load and the patient reported outcome measures (PROMs): Chronic Respiratory Infection Symptom Score (CRISS), the Cystic Fibrosis Questionnaire-Revised (CFQ-R); FEV1, blood leukocyte count, and inflammatory markers. Eighty nine participants in fifteen US and EU centres were randomized, 78 completed the 14-day treatment period. Cysteamine had no significant effect on sputum bacterial load, however technical difficulties limited interpretation. The most consistent findings were for cysteamine 450mg twice daily that had effects additional to that observed with placebo, with improved symptoms, CRISS additional 9.85 points (95% CI 0.02, 19.7) p = 0.05, reduced blood leukocyte count by 2.46x109 /l (95% CI 0.11, 4.80), p = 0.041 and reduced CRP by geometric mean 2.57 nmol/l (95% CI 0.15, 0.99), p = 0.049.

CONCLUSION

In this exploratory study cysteamine appeared to be safe and well-tolerated. Future pivotal trials investigating the utility of cysteamine in pulmonary exacerbations of CF need to include the cysteamine 450mg doses and CRISS and blood leukocyte count as outcome measures.

CLINICAL TRIAL REGISTRATION

NCT03000348; www.clinicaltrials.gov.

Redox-Modulating Agents in the Treatment of Viral Infections

Viruses use cell machinery to replicate their genome and produce viral proteins. For this reason, several intracellular factors, including the redox state, might directly or indirectly affect the progression and outcome of viral infection. In physiological conditions, the redox balance between oxidant and antioxidant species is maintained by enzymatic and non-enzymatic systems, and it finely regulates several cell functions. Different viruses break this equilibrium and induce an oxidative stress that in turn facilitates specific steps of the virus lifecycle and activates an inflammatory response. In this context, many studies highlighted the importance of redox-sensitive pathways as novel cell-based targets for therapies aimed at blocking both viral replication and virus-induced inflammation. In the review, we discuss the most recent findings in this field. In particular, we describe the effects of natural or synthetic redox-modulating molecules in inhibiting DNA or RNA virus replication as well as inflammatory pathways. The importance of the antioxidant transcription factor Nrf2 is also discussed. Most of the data reported here are on influenza virus infection. We believe that this approach could be usefully applied to fight other acute respiratory viral infections characterized by a strong inflammatory response, like COVID-19.

Therapeutic Applications of Cysteamine and Cystamine in Neurodegenerative and Neuropsychiatric Diseases

Current medications for neurodegenerative and neuropsychiatric diseases such as Alzheimer's disease (AD), Huntington's disease (HD), Parkinson's disease (PD), and Schizophrenia mainly target disease symptoms. Thus, there is an urgent need to develop novel therapeutics that can delay, halt or reverse disease progression. AD, HD, PD, and schizophrenia are characterized by elevated oxidative and nitrosative stress, which play a central role in pathogenesis. Clinical trials utilizing antioxidants to counter disease progression have largely been unsuccessful. Most antioxidants are relatively non-specific and do not adequately target neuroprotective pathways. Accordingly, a search for agents that restore redox balance as well as halt or reverse neuronal loss is underway. The small molecules, cysteamine, the decarboxylated derivative of the amino acid cysteine, and cystamine, the oxidized form of cysteamine, respectively, mitigate oxidative stress and inflammation and upregulate neuroprotective pathways involving brain-derived neurotrophic factor (BDNF) and Nuclear factor erythroid 2-related factor 2 (Nrf2) signaling. Cysteamine can traverse the blood brain barrier, a desirable characteristic of drugs targeting neurodegeneration. This review addresses recent developments in the use of these aminothiols to counter neurodegeneration and neuropsychiatric deficits.

Metabolic pathway catalyzed by Vanin-1 pantetheinase plays a suppressive role in influenza virus replication in human alveolar epithelial A549 cells

Our previous analysis of gene expression profiles in the peripheral blood from patients with influenza A (H1N1) pdm09 pneumonia revealed elevated transcription levels of the vanin-1 (vascular non-inflammatory molecule 1, VNN1) gene, which encodes an epithelial ectoenzyme with pantetheinase activity involved in recycling coenzyme A. Here, to elucidate the role of VNN1 in influenza A virus (IAV) H1N1 infection, we investigated the change of VNN1 expression in the context of IAV infection and the effects of its related substances, i.e., its direct substrate pantetheine and its two metabolites pantothenic acid and cysteamine on the replication of IAV in the human alveolar epithelial carcinoma cell line A549. The messenger RNA expression of VNN1 in A549 cells was significantly increased (by 4.9-fold) after IAV infection under an elevated concentration of pantetheine. Moreover, VNN1 mRNA levels were elevated by > 100-fold in response to pro-inflammatory cytokines, especially TNF-α and IL-1β. Pantetheine significantly reduced the IAV replication and IAV Matrix 1 (M1) mRNA levels when it was administered prior to and during infection. In addition, cysteamine treatment during IAV infection significantly reduced the viral replication and IAV M1 mRNA levels, whereas pantothenic acid did not. These findings suggest that the metabolic pathway catalyzed by VNN1 pantetheinase plays a suppressive role in IAV infection in the respiratory tract, especially in severe conditions under hypercytokinemia.

WR1065 mitigates AZT-ddI-induced mutagenesis and inhibits viral replication

The success of nucleoside reverse transcriptase inhibitors (NRTIs) in treating HIV-1 infection and reducing mother-to-child transmission of the virus during pregnancy is accompanied by evidence that NRTIs cause long-term health risks for cancer and mitochondrial disease. Thus, agents that mitigate toxicities of the current combination drug therapies are needed. Previous work had shown that the NRTI-drug pair zidovudine (AZT)-didanosine (ddI) was highly cytotoxic and mutagenic; thus, we conducted preliminary studies to investigate the ability of the active moiety of amifostine, WR1065, to protect against the deleterious effects of this NRTI-drug pair. In TK6 cells exposed to 100 muM AZT-ddI (equimolar) for 3 days with or without 150 muM WR1065, WR1065 enhanced long-term cell survival and significantly reduced AZT-ddI-induced mutations. Follow-up studies were conducted to determine if coexposure to AZT and WR1065 abrogated the antiretroviral efficacy of AZT. In human T-cell blasts infected with HIV-1 in culture, inhibition of p24 protein production was observed in cells treated with 10 muM AZT in the absence or presence of 5-1,000 muM WR1065. Surprisingly, WR1065 alone exhibited dose-related inhibition of HIV-1 p24 protein production. WR1065 also had antiviral efficacy against three species of adenovirus and influenza A and B. Intracellular levels of unbound WR1065 were measured following in vitro/in vivo drug exposure. These pilot study results indicate that WR1065, at low intracellular levels, has cytoprotective and antimutagenic activities against the most mutagenic pair of NRTIs and has broad spectrum antiviral effects. These findings suggest that the activities have a possible common mode of action that merits further investigation.

Disulfide exchange in domain 2 of CD4 is required for entry of HIV-1

CD4, a member of the immunoglobulin superfamily of receptors that mediates cell-cell interactions in the immune system, is the primary receptor for HIV-1. The extracellular portion of CD4 is a concatenation of four immunoglobulin-like domains, D1 to D4. The D1, D2 and D4 domains each contain a disulfide bond. We show here that the D2 disulfide bond is redox-active. The redox state of the thiols (disulfide versus dithiol) appeared to be regulated by thioredoxin, which is secreted by CD4(+) T cells. Locking the CD4 and the thioredoxin active-site dithiols in the reduced state with a hydrophilic trivalent arsenical blocked entry of HIV-1 into susceptible cells. These findings indicate that redox changes in CD4 D2 are important for HIV-1 entry and represent a new target for HIV-1 entry inhibitors.

Synthesis and in vitro anti-HIV activity in human monocyte-derived macrophages of 2-oxothiazolidine-4(R)-carboxylic acid derivatives

Oxidative stress and glutathione (GSH) deficit may play an important role in HIV infection pathogenesis, and oral administration of GSH-replenishing drugs such as N-acetylcysteine (NAC) and 2-oxothiazolidine-4(R)-carboxylic acid (OTC) may be associated with an increased survival rate of HIV-infected patients. Nevertheless, beneficial effects of these molecules are restricted in vivo by the high concentrations that are necessary to obtain biological effects, rapid extracellular metabolization, and low availability and plasma concentrations. We synthesized OTC derivatives that are more lipophilic than OTC and theoretically able to overcome these limitations and to generate, in addition to cysteine, other substrates of the gamma-glutamyl cycle. Their antiviral effects were investigated in human HIV-1/Ba-L-infected monocyte-derived macrophages. In our experimental conditions, OTC exhibited anti-HIV-1 effects and little cytotoxicity at high doses. None of the nine tested derivatives showed higher cytotoxicity than OTC, nor anti-HIV-1/Ba-L activity.

Zinc ejection as a new rationale for the use of cystamine and related disulfide-containing antiviral agents in the treatment of AIDS

The highly conserved and mutationally intolerant retroviral zinc finger motif of the HIV-1 nucleocapsid protein (NC) is an attractive target for drug therapy due to its participation in multiple stages of the viral replication cycle. A literature search identified cystamine, thiamine disulfide, and disulfiram as compounds that have been shown to inhibit HIV-1 replication by poorly defined mechanisms and that have electrophilic functional groups that might react with the metal-coordinating sulfur atoms of the retroviral zinc fingers and cause zinc ejection. 1H NMR studies reveal that these compounds readily eject zinc from synthetic peptides with sequences corresponding to the HIV-1 NC zinc fingers, as well as from the intact HIV-1 NC protein. In contrast, the reduced forms of disulfiram and cystamine, diethyl dithiocarbamate and cysteamine, respectively, were found to be ineffective at zinc ejection, although cysteamine formed a transient complex with the zinc fingers. Studies with HIV-1-infected human T-cells and monocyte/macrophage cultures revealed that cystamine and cysteamine possess significant antiviral properties at nontoxic concentrations, which warrant their consideration as therapeutically useful anti-HIV agents.