1 Department of Biology, School of Health, Concordia University, Montréal, Québec, Canada.
2 Department of Chemical and Materials Engineering, Center for Applied Synthetic Biology, Concordia University, Montréal, Québec, Canada.
3 Department of Electrical and Computer Engineering, School of Health, Concordia University, Montréal, Québec, Canada.
4 Department of Health Kinesiology & Applied Physiology, School of Health, Concordia University, Montréal, Québec, Canada.

Introduction: Cancers often drive T cells toward an exhausted state characterized by impaired cytotoxicity and upregulation of inhibitory receptors (PD-1, TIM-3, CD38) and transcriptional regulators (TOX, NFATc1). Repeated stimulation in vitro is used to model this process, reflecting chronic antigen exposure in the tumor microenvironment. Stress-derived catecholamines further drive dysfunction through ß-adrenergic receptor (ß-AR) signaling. Here, we examined the impact of nebivolol, an atypical ß1-AR blocker with ß2-biased agonist activity, on T-cell exhaustion and cytotoxicity against breast cancer cells.

Methods: Human CD3+ T cells from healthy participants were activated once (early activation) or four times (repeated activation) using CD3/CD28/CD2 T cell activator. Cells were treated in vitro with nebivolol, terbutaline (ß2-agonist), isoproterenol (ß1/ß2-agonist), and metoprolol (ß1-blocker). Exhaustion markers, including PD-1, TIM-3, CD38, and TOX, were measured by flow cytometry and RT-qPCR; NFATc1 by western blot; TNF and IFN-? by ELISA, and cytotoxicity against MCF-7 breast carcinoma cells by co-culture assays. Disruption of the ß2-AR gene (ADRB2) was achieved using CRISPR/Cas9.

Results: Nebivolol reduced the proportion of TIM-3+CD38+PD-1+ T cells, downregulated TOX and nuclear NFATc1, and restored ADRB2 expression under repeated activation conditions. Nebivolol enhanced TNF secretion and improved cytotoxicity against MCF-7 cells. In contrast, terbutaline and isoproterenol had no significant effect on exhaustion markers or cytotoxicity. Metoprolol did not inhibit nebivolol's activity, indicating that its effects are not ß1-AR-dependent. Disruption of ADRB2 indicated that nebivolol's anti-exhaustion effects are mediated by ß2-AR.

Discussion: These findings show that nebivolol reinvigorates CD4+ and CD8+ T cells following repeated activation, restoring their cytotoxic function against breast cancer cells in vitro. The immunomodulatory activity of Nebivolol is independent of ß1-AR and mediated through ß2-AR, suggesting that biased ß2-AR signaling may represent a potential strategy for modulating T cell exhaustion in the tumor microenvironment.