Table 1.

Summary of the main findings from key original articles investigating non-cardiac applications of digoxin and other cardiac glycosides

Manuscript title	Publication year	Main biomedical/molecular findings	Main histological findings	Ref.
Cardiac glycosides inhibit p53 synthesis by a mechanism relieved by Src or MAPK inhibition	2009	Activation of Src/MAPK signaling pathways, resulting in reduction of p53 protein synthesis	NA	[72]
Human cytomegalovirus inhibition by cardiac glycosides: Evidence for involvement of the HERG gene	2012	CG reduced expression of the potassium channel gene, hERG, and reduced NF-κB levels	NA	[85]
Digoxin Suppresses HIV-1 Replication by Altering Viral RNA Processing	2013	Reduction in HIV-1 viral mRNAs encoding structural proteins, with reduced synthesis of HIV-1 structural protein; altered viral RNA splice site use leading to loss of essential viral factor Rev; changed activity of CLK family of SR protein kinases and modification of SR proteins	NA	[91]
A novel cell-based high-throughput screen for inhibitors of HIV-1 gene expression and budding identifies the cardiac glycosides	2014	Na-K ATPase- dependent but intracellular Ca2+-independent inhibition of HIV-1 gene expression at the post-integration stage of the viral life cycle	NA	[90]
Digoxin Suppresses Tumor Malignancy through Inhibiting Multiple Src-Related Signaling Pathways in Non-Small Cell Lung Cancer	2015	Inhibition of proliferation, invasion, migration, and colony formation of A549 lung cancer cells; suppression of Src and related protein activity; reduced EGFR and STAT3 activity	NA	[75]
Synergistic effects of ion transporter and MAP kinase pathway inhibitors in melanoma	2016	Inhibition of the ATP1A1 Na+/K+ pump, which is highly expressed in melanoma, resulting in selective toxicity to melanoma cells. Digoxin was also additive or synergistic with MEK inhibitor and/or BRAF inhibitor to induce cell death in melanoma cells; increased intracellular acidification, mitochondrial calcium dysregulation, and ATP depletion in melanoma cells	NA	[79]
Small-molecule TFEB pathway agonists that ameliorate metabolic syndrome in mice and extend C. elegans lifespan	2017	Activated TFEB, conferred hepatoprotection against diet-induced steatosis in mice, and extended lifespan of Caenorhabditis elegans	Amelioration of high-fat diet-induced steatosis, reversal of hepatocyte p62/SQSTM1 accumulation, suggesting enhanced autophagic flux	[62]
Targeting Intracellular Ion Homeostasis for the Control of Respiratory Syncytial Virus	2018	Findings suggested digoxin-mediated inhibition of RSV transcription and/or replication, likely dependent on changes in intracellular Na+ and K+	NA	[82]
Digoxin Suppresses PKM2 Promoted HIF-1α Transactivation in Steatohepatitis	2018	Binding of PKM2 by digoxin downregulated HIF-1α transactivation to decrease sterile inflammation in the liver. Digoxin suppressed ROS production both in vivo and in vitro from hepatocytes and immune cells	Reduction in hepatic damage, steatosis, and inflammation induced by endotoxin, high fat diet, or alcohol	[27]
Digoxin improves steatohepatitis with differential involvement of liver cell subsets in mice through inhibition of PKM2 transactivation	2019	Digoxin downregulated PKM2-PKM2-HIF-1α axis and attenuated inflammasome activity in macrophages and hepatic oxidative stress response	Reduction of high fat diet-induced hepatic damage, steatosis, and liver inflammation	[28]
Antiviral activity of digoxin and ouabain against SARS-CoV-2 infection and its implication for COVID-19	2020	Inhibition of viral mRNA expression, copy number, and viral protein expression at the post entry stage of the viral life cycle	NA	[81]
Classical Drug Digitoxin Inhibits Influenza Cytokine Storm, With Implications for COVID-19 therapy	2020	Suppression of levels of the cytokines TNF-α, GRO/KC, MIP2, MCP1, and IFN-γ during cytokine storm	No difference in density of immune cells in rat lung sections, comparing digitoxin-treated and control lungs	[84]
Inhibition of the IL-17A axis in adipocytes suppresses diet-induced obesity and metabolic disorders in mice	2021	Digoxin inhibition of RORγT activity suppressed the IL-17A axis, thus preventing diet-induced obesity, metabolic alterations, and liver injury	Prevention of high fat diet-induced hepatic lipid accumulation, reduced fibrosis, increased browning of adipose tissue	[59]

TFEB: Transcription factor EB; PKM2: Pyruvate kinase M2; IL-17A: Interleukin-17A; MAPK: Mitogen-activated protein kinase; CG: Cardiac glycoside; NF-κB: Nuclear factor-kappaB; CLK: Cdc2-like kinases; SR: Serine-arginine; EGFR: Epidermal growth factor receptor; MEK: MAP kinase kinase; RSV: Respiratory syncytial virus; HIF-1α: Hypoxia-inducible factor 1-alpha; SARS-CoV-2: Severe acute respiratory syndrome coronavirus 2; COVID-19: Coronavirus disease 2019; TNF-α: Tumor necrosis factor-alpha; GRO/KC: Growth-regulated oncogene/keratinocyte chemoattractant; MIP2: Macrophage inflammatory protein 2; MCP1: Monocyte chemoattractant protein-1; IFNγ: Interferon-gamma; RORγT: Retinoid-related orphan receptor-gamma; NA: No application; ROS: Reactive oxygen species; STAT3: Signal transducer and activator of transcription 3.