Effect of verapamil on T-lymphocyte activation in vitro

The Ca2+ Channel Blocker Verapamil Inhibits the In Vitro Activation and Function of T Lymphocytes: A 2022 Reappraisal

Ca²⁺ channel blockers (CCBs) are commonly used to treat different cardiovascular conditions. These drugs disrupt the intracellular Ca²⁺ signaling network, inhibiting numerous cellular functions in different cells, including T lymphocytes. We explored the effect of the CCB verapamil on normal human peripheral blood T cell activation, proliferation, and cytokine production. Cells were activated by ligating CD3 or CD3/CD28 in the presence or absence of verapamil, and the expression of activation-induced cell surface molecules (CD25, CD40L, CD69, PD-1, and OX40), cell proliferation, and cytokine release were assessed by flow cytometry. Verapamil exerted a dose-dependent inhibitory effect on the expression of all the activation-induced cell surface molecules tested. In addition, verapamil diminished T cell proliferation induced in response to CD3/CD28 stimulation. Likewise, the production of Th1/Th17 and Th2 cytokines was also reduced by verapamil. Our data substantiate a potent in vitro suppressive effect of verapamil on T lymphocytes, a fact that might be relevant in patients receiving CCBs.

In vitro analysis of verapamil-induced immunosuppression: potent inhibition of T cell motility and lymphocytic transmigration through allogeneic endothelial cells

BACKGROUND

Cyclosporine A (CsA) and tacrolimus prevent proliferation but not transendothelial migration of alloreactive lymphocytes into donor organs. As a result, serious adverse effects, such as nephrotoxicity and neurotoxicity, have been observed under CsA/tacrolimus therapy. The incorporation of new drugs with infiltration blocking properties might enhance the efficacy of the current immunosuppressive protocol, allowing lower CsA/tacrolimus dosage. Because Ca2+ plays a critical role in cell-cell interaction, the Ca2+-channel blocker verapamil might be a good cany. didate for supporting CsA/tacrolimus-based therapy.

METHODS

A T-cell endothelial cell coculture model or immobilized immunoglobulin G globulin chimeras were employed to investigate how S- and R- verapamil interfere with the lymphocytic infiltration process. The expression and arrangement of membranous adhesion receptors and cytoskeletal F-actin filaments were analyzed by fluorometric method in the presence of. verapamil.

RESULTS

Both verapamil enantiomers strongly inhibited lymphocyte infiltration. CD4+ and CD8+ T-cells were influenced to a similar extent with regard to horizontal locomotion (CD4+=CD8+), but to a different extent with regard to adhesion and penetration (CD4+ > CD8+). Moreover, penetration was blocked to a higher extent than was adhesion. ID50-values were 31 microM (CD4+-adhesion) and 11 microM (CD4+-penetration). Verapamil reduced P-selectin expression on endothelial cells and effectively down-regulated binding of T-cells to immobilized P-selectin immunoglobulin G globulins (ID50=4.4 microM; CD4+). A verapamil-induced reduction of intracellular F-actin in T-lymphocytes was proven to be mainly responsible for diminished cell locomotion.

CONCLUSIONS

The prevention of CD4+ T-cell penetration by verapamil might argue for its use as an adjunct to CsA/tacrolimus-based immunosuppressive therapy.

CD4+ TCR alpha beta+ T-cell clones derived shortly after allogeneic bone marrow transplantation: theophyllamine and verapamil inhibit proliferation of functionally heterogeneous T-cells

CD4+ TCR alpha beta+ T-cell clones were prepared from three CML-patients 4-6 weeks after allogeneic bone marrow transplantation and the effects of theophyllamine and verapamil on clonal growth then assessed. Both drugs inhibited PHA-stimulated autocrine proliferation of clones as well as proliferation of clones dependent on exogenous growth factors. Inhibition was seen when using different accessory cells (PBM or BCL) during T-cell activation, and both for IL2- and IL4-dependent proliferation of previously activated T-cells. The isomer R-verapamil inhibited PHA-stimulated proliferation as well as IL2- and IL4-dependent T-cell proliferation. The drugs also inhibited proliferation of CD8+ T-cells. Although the T-cell clones were functionally heterogeneous and were derived from different patients and priming cultures, both drugs inhibited all clones investigated. However, the degree of inhibition varied between different clones.

The additive effect of certain drugs on the cyclosporine A inhibition of human T-cell proliferation. Studies using theophyllamine, warfarin, verapamil and dipyridamol

The inhibitory effect of Cyclosporine A (CsA) when combined with theophyllamine, warfarin, verapamil or dipyridamol on in vitro proliferation of human T lymphocyte was investigated. All drugs caused an additional inhibition of PHA activation compared with CsA alone, also when the CD8-negative and -positive subsets were tested separately. This effect was dose-dependent for all drugs. Theophyllamine, verapamil and warfarin had to be added early during PHA-stimulated T-cell activation to cause maximal inhibition. Also when testing the proliferative response in mixed lymphocyte cultures, the drugs showed a dose-dependent additional inhibition compared with CsA alone. CsA alone caused no inhibition of lymphokine-dependent growth of T-cell lines, whereas all four drugs caused a weak inhibition in this test system.

Decreased lymphocyte blastogenesis, IL2 production and NK activity following nifedipine administration to healthy humans

The effects of a single oral dose of nifedipine on part of the immune response in healthy humans has been investigated in terms of two different immune functions: T lymphocyte proliferation and NK activity. Both functions are known to require calcium ions. Ten healthy subjects were bled before and 30 min, and 4 and 24 h after receiving 10 mg nifedipine. Lymphocyte proliferation, both in mitogen-activated lymphocyte cultures, and in autologous and allogeneic mixed lymphocyte reactions, was significantly reduced (up to 48%) 30 min after drug administration and reverted to normal 4 h later. The inhibition could be attributed to reduction in IL2 production by the T cells isolated 30 min following the administration of nifedipine, since they normally express IL2-receptors. The addition of recombinant IL2 of 200 U.ml-1 to the cell cultures restored their responsiveness. NK activity was significantly reduced 30 min and 4 h after drug administration and returned to normal at the 24th h. This function was also restored by the addition of IL2. The data suggest that calcium channel blockers may inhibit, at least transiently, lymphocyte functions in vivo.

Modulation of murine in vitro immune response by verapamil (V)

Functionally distinct lymphocyte subsets differ with regard to necessary activation signals. In selected circumstances lymphocyte activation has been shown to be critically dependent upon transcellular calcium influx. Whether calcium plays a central role in the activation of all lymphocytes remains to be determined. The effect of the calcium channel blocker verapamil on the induction of murine cytotoxic T lymphocytes (CTL), suppressor cells, T helper cells, and B cells was investigated. Verapamil (V) was found to inhibit the induction of cytotoxic effector cells. V acted primarily on the afferent limb of this immune response, was synergistic with cyclosporin A (CsA), and its effects could be largely reversed by the addition of exogenous helper factors. V also inhibited B cell proliferation in response to anti-mouse IgM in the presence of 2-mercaptoethanol, but in the absence of cognate or non-cognate T cell help. In contrast to this, V did not inhibit the activation of cells capable of inducing B cell proliferation nor did it inhibit the induction of suppressor cells. The selective suppression of V is discussed in terms of activation requirements of CTL, suppressor cells and helper cell subsets.

Dipyridamol inhibits activation of human T lymphocytes in vitro

The effect of dipyridamol on T-lymphocyte activation was investigated. The drug did not have an irreversible toxic effect on T lymphocytes. Dipyridamol inhibited both PHA- and mumps-stimulated proliferation and the proliferative response in mixed lymphocyte cultures. The drug inhibited PHA-stimulated proliferation independent of the time when it was added during the culture period. The PHA-stimulated expression of interleukin-2 (IL-2) receptors and IL-2 production (at least for low concentrations) was not inhibited. Dipyridamol inhibited IL-2-dependent growth of T cell lines. The drug caused no inhibition when present only during antigenic pulsing.

T lymphocyte responses to Coxsackie B4 and mumps virus. I. Influence of HLA-DR restriction elements

The proliferative T lymphocyte responses to Coxsackie B4-, mumps- and varicella-zoster viral antigens were characterized. No significant difference in responsiveness was found between healthy individuals and patients with Type 1 (insulin-dependent) diabetes mellitus. Theophyllamine and verapamil decreased antigen-stimulated proliferation, whereas indomethacin in physiologic concentrations (1 microgram/ml) slightly increased proliferation. A major part of the response seemed to be restricted by HLA-DR molecules. Furthermore, for the mumps antigen the DR3- and DR4-determinants which are associated with Type 1 diabetes, seemed to have a different regulatory function on the T lymphocyte response in that an increased frequency of low responders was found among DR3 positive individuals and an increased frequency of high responders among DR4 positives.