Perillyl alcohol inhibits TCR-mediated [Ca(2+)](i) signaling, alters cell shape and motility, and induces apoptosis in T lymphocytes

A minimally invasive optical trapping system to understand cellular interactions at onset of an immune response

T-cells and antigen presenting cells are an essential part of the adaptive immune response system and how they interact is crucial in how the body effectively fights infection or responds to vaccines. Much of the experimental work studying interaction forces between cells has looked at the average properties of bulk samples of cells or applied microscopy to image the dynamic contact between these cells. In this paper we present a novel optical trapping technique for interrogating the force of this interaction and measuring relative interaction forces at the single-cell level. A triple-spot optical trap is used to directly manipulate the cells of interest without introducing foreign bodies such as beads to the system. The optical trap is used to directly control the initiation of cell-cell contact and, subsequently to terminate the interaction at a defined time point. The laser beam power required to separate immune cell pairs is determined and correlates with the force applied by the optical trap. As proof of concept, the antigen-specific increase in interaction force between a dendritic cell and a specific T-cell is demonstrated. Furthermore, it is demonstrated that this interaction force is completely abrogated when T-cell signalling is blocked. As a result the potential of using optical trapping to interrogate cellular interactions at the single cell level without the need to introduce foreign bodies such as beads is clearly demonstrated.

Accurate position tracking of optically trapped live cells

Optical trapping is a powerful tool in Life Science research and is becoming common place in many microscopy laboratories and facilities. There is a growing need to directly trap the cells of interest rather than introduce beads to the sample that can affect the fundamental biological functions of the sample and impact on the very properties the user wishes to observe and measure. However, instabilities while tracking large inhomogeneous objects, such as cells, can make tracking position, calibrating trap strength and making reliable measurements challenging. These instabilities often manifest themselves as cell roll or re-orientation and can occur as a result of viscous drag forces and thermal convection, as well as spontaneously due to Brownian forces. In this paper we discuss and mathematically model the cause of this roll and present several experimental approaches for tackling these issues, including using a novel beam profile consisting of three closely spaced traps and tracking a trapped object by analysing fluorescence images. The approaches presented here trap T cells which form part of the adaptive immune response system, but in principle can be applied to a wide range of samples where the size and inhomogeneous nature of the trapped object can hinder particle tracking experiments.

Perillyl alcohol suppresses antigen-induced immune responses in the lung

Perillyl alcohol (POH) is an isoprenoid which inhibits farnesyl transferase and geranylgeranyl transferase, key enzymes that induce conformational and functional changes in small G proteins to conduct signal production for cell proliferation. Thus, it has been tried for the treatment of cancers. However, although it affects the proliferation of immunocytes, its influence on immune responses has been examined in only a few studies. Notably, its effect on antigen-induced immune responses has not been studied. In this study, we examined whether POH suppresses Ag-induced immune responses with a mouse model of allergic airway inflammation. POH treatment of sensitized mice suppressed proliferation and cytokine production in Ag-stimulated spleen cells or CD4(+) T cells. Further, sensitized mice received aerosolized OVA to induce allergic airway inflammation, and some mice received POH treatment. POH significantly suppressed indicators of allergic airway inflammation such as airway eosinophilia. Cytokine production in thoracic lymph nodes was also significantly suppressed. These results demonstrate that POH suppresses antigen-induced immune responses in the lung. Considering that it exists naturally, POH could be a novel preventive or therapeutic option for immunologic lung disorders such as asthma with minimal side effects.

A review on anti-inflammatory activity of monoterpenes

Faced with the need to find new anti-inflammatory agents, great effort has been expended on the development of drugs for the treatment of inflammation. This disorder reduces the quality of life and overall average productivity, causing huge financial losses. In this review the anti-inflammatory activity of 32 bioactive monoterpenes found in essential oils is discussed. The data demonstrate the pharmacological potential of this group of natural chemicals to act as anti-inflammatory drugs.

Tipifarnib-induced apoptosis in acute myeloid leukemia and multiple myeloma cells depends on Ca2+ influx through plasma membrane Ca2+ channels

A major contributing factor to the high mortality rate associated with acute myeloid leukemia and multiple myeloma is the development of resistance to chemotherapy. We have shown that the combination of tipifarnib, a nonpeptidomimetic farnesyltransferase inhibitor (FTI), with bortezomib, a proteosome inhibitor, promotes synergistic death and overcomes de novo drug resistance in acute myeloid leukemia cell lines. Experiments were undertaken to identify the molecular mechanisms by which tipifarnib produces cell death in acute myeloid leukemia and multiple myeloma cell lines (U937 and 8226, respectively). Tipifarnib, but not other FTIs tested [N-[4-[2(R)-amino-3-mercaptopropyl]amino-2-phenylbenzoyl]methionine methyl ester trifluoroacetate salt (FTI-277) and 2'-methyl-5-((((1-trityl-1H-imidazol-4-yl)methyl)amino)methyl)-[1,1'-biphenyl]-2-carboxylic acid (FTI-2153), promotes elevations in intracellular free-calcium concentrations ([Ca(2+)](i)) in both cell lines. These elevations in [Ca(2+)](i) were accompanied by highly dynamic plasmalemmal blebbing and frequently resulted in membrane lysis. The tipifarnib-induced elevations in [Ca(2+)](i) were not blocked by thapsigargin or ruthenium red, but were inhibited by application of Ca(2+)-free extracellular solution and by the Ca(2+) channel blockers Gd(3+) and La(3+). Conversely, 2-aminoethoxydiphenyl borate (2-APB) potentiated the tipifarnib-evoked [Ca(2+)](i) overload. Preventing Ca(2+) influx diminished tipifarnib-evoked cell death, whereas 2-APB potentiated this effect, demonstrating a link between tipifarnib-induced Ca(2+) influx and apoptosis. These data suggest that tipifarnib exerts its effects by acting on a membrane channel with pharmacological properties consistent with store-operated channels containing the Orai3 subunit. It is noteworthy that Orai3 transcripts were found to be expressed at lower levels in tipifarnib-resistant 8226/R5 cells. Our results indicate tipifarnib causes cell death via a novel mechanism involving activation of a plasma membrane Ca(2+) channel and intracellular Ca(2+) overload.

Potent farnesyltransferase inhibitor ABT-100 abrogates acute allograft rejection

BACKGROUND

Farnesyltransferase inhibitors (FTIs) inhibit the function of Ras, a GTPase involved in carcinogenesis and T cell activation. We evaluated the in vitro and in vivo immunomodulatory properties of a rationally designed FTI, ABT-100.

METHODS

The effects of ABT-100 on human peripheral blood mononuclear cell (PBMC) proliferation and the expression of the T cell activation markers CD25 and CD69 were studied. In a Wistar to Lewis rat heterotopic cardiac transplant model, ABT-100 was orally dosed alone or with a subtherapeutic course of cyclosporine (CsA). The degree of graft immune cell infiltrate was determined.

RESULTS

ABT-100 potently inhibited PBMC proliferation, but did not decrease expression of CD25 and CD69 during activation. Treatment with 25, 50 and 100 mg/kg ABT-100 BID increased allograft mean survival time (MST) to 12.8+/-3 days, 13.5+/-5 days and 13.8+/-3 days, respectively (vs 6.5+/-3 days for controls, p<0.001 by log rank). A subtherapeutic course of CsA increased MST to 12.7+/-3 days (p<0.001 vs control). Combination with ABT-100 at 25 and 100 mg/kg BID improved MST to 18.7+/-5 days and 19.5+/-4 days (both p<0.001 vs control and respective monotherapy groups). ABT-100 treatment at 100 mg/kg BID significant decreased the amount of graft infiltrate (2.5+/-4 mononuclear cells/high power field (hpf) vs 29+/-11 cells/hpf, p<0.001).

CONCLUSIONS

This is the first report that a specific FTI delays the development of acute rejection and supports the strategy of inhibiting Ras to impart immunomodulation. The antirejection and anticarcinogenic effects make FTIs a potentially useful adjunct in the antirejection regimens of malignancy-prone organ transplant recipients.

Immunosuppression for heart transplantation: where are we now?

The success of cardiac transplantation is largely attributable to the development of effective immunosuppressive regimens. The introduction of calcineurin inhibitors was pivotal in reducing the frequency of acute rejection and improving early survival. Newer agents, including mycophenolate mofetil (MMF) and proliferation-signal inhibitors, have shown promise in further reducing acute-rejection rates and, notably, reducing the frequency of cardiac allograft vasculopathy, which limits long-term graft survival. The introduction of first-year intravascular ultrasonography results as a surrogate marker for outcome after cardiac transplantation has helped assessment of the efficacy of immunosuppressive medications. Proliferation-signal inhibitors and MMF were shown by this imaging method to reduce cardiac allograft vasculopathy. The combination of these drugs, in tandem with the weaning of patients off calcineurin inhibitors, has been shown to reverse calcineurin-inhibitor-related nephrotoxic effects. A randomized trial that compared three of the more common immunosuppressive regimens suggested that tacrolimus and MMF are associated with a reduction in the frequency of rejection episodes that require treatment and have the fewest adverse effects. Finally, the use of statins has brought added benefit to immunosuppressive regimens by improving outcomes after cardiac transplantation, reportedly because of an immunomodulatory property. Promising newer immunosuppressive agents await clinical trials. This review presents an overview of the emerging data on immunosuppressive therapy for cardiac transplantation.

Ten-Year Follow-Up of a Randomized Trial of Pravastatin in Heart Transplant Patients

BACKGROUND

Outcomes from this trial's first year data demonstrated significant benefit in heart transplant patients treated with pravastatin in cholesterol levels, survival, rejection with hemodynamic compromise, the development of cardiac allograft vasculopathy, and decreased natural killer cell cytotoxicity. Other heart transplant studies have shown similar benefit. We now report the 10-year follow-up of this study.

METHODS

Ninety-seven heart transplant recipients were randomized to pravastatin (n = 47) or no pravastatin (n = 50) within 2 weeks after surgery both in combination with cyclosporine and corticosteroids. Ten-year outcomes include survival, cholesterol levels, and development of cardiac allograft vasculopathy documented by coronary angiography.

RESULTS

Forty-two percent of the control patients crossed over to pravastatin treatment during the second year of the study, and 81% of the control patients were eventually placed on statin therapy by the 10-year follow-up. The control group had subsequent low and comparable cholesterol levels in Years 2 to 10 of the study compared with the patients originally randomized to pravastatin. Intent-to-treat analysis demonstrated that the pravastatin group compared with control had increased 10-year survival (68% vs 48%, p = 0.026). The 10-year freedom from angiographic cardiac allograft vasculopathy and/or death in the pravastatin group was significantly greater compared with the control group (43% vs 20%, p = 0.009).

CONCLUSION

The 10-year follow-up of this study suggests that the use of pravastatin in heart transplant patients maintains survival benefit and appears to reduce the development of cardiac allograft vasculopathy.

The effect of HMG-CoA reductase inhibitors on chronic allograft rejection

Hydroxy-methyl-glutaryl coenzyme A (HMG-CoA) reductase inhibitors have pleiotropic actions that affect many systems other than lowering blood cholesterol concentrations. Hypercholesterolaemia is an adverse effect of immunosuppressive drug therapy and hence it is a common finding after organ transplantation. HMG-CoA reductase inhibitors lower cholesterol concentrations in transplant recipients but they also offer additional benefits. Since they impair the production of mevalonate, they reduce the concentrations of downstream products including farnesyl and geranyl phosphate. These isoprenoid moieties are required for protein prenylation and HMG-CoA reductase inhibitors impair this function in some cells. This action affects the immune system, especially in patients taking cyclosporin, and has been proposed as the mechanism whereby these drugs increase the half-life of transplanted organs. Other mechanisms have also been proposed including an increase in the free fraction of cyclosporin and a reduction in the time that low density lipoprotein (LDL) spends in blood. The latter effect reduces the extent of oxidation of LDL and hence reduces the damage caused by oxidised LDL. Chronic rejection is poorly understood but appears to involve both immune and non-immune processes. HMG-CoA reductase inhibitors affect both processes. At present, the evidence of benefit from statin prescription is confined to heart and kidney transplant recipients but it is likely that recipients of other organ transplants would also benefit. Drug interactions between cyclosporin and HMG-CoA reductase inhibitors are a limiting factor to their use. Pravastatin appears to be the best HMG-CoA reductase inhibitor for organ transplant recipients because of its lesser potential to interact with cyclosporin and hence cause myositis, which may thus allow higher doses to be used. Other, non-immunosuppressive drugs (including diltiazem and ketoconazole) have been shown to reduce transplant organ damage by unknown mechanisms and are widely prescribed in some transplant centres. More specific inhibitors of protein prenylation may afford useful immunosuppression, thereby prolonging transplant organ half-lives and also reducing the risk of cancer.

Statins in solid organ transplantation: is there an immunosuppressive effect?

Cardiac allograft vasculopathy is one of the major causes of mortality late after heart transplantation. This disease process occurs to a lesser extent in patients with other donor organs; however, a long-term graft dysfunction is similarly described in kidney, liver and lung transplant recipients. There are multiple immune and nonimmune risk factors associated with this vasculopathic disease process, one of which includes hyperlipidemia. Use of lipid lowering agents, specifically HMG-CoA reductase inhibitors (statins) was initially reported to have possible immunosuppressive effects in a single center study of heart transplant recipients. This has not been observed in kidney transplant recipients; however, a large randomized trial demonstrated a significant cardiovascular risk reduction in fluvastatin-treated kidney transplant patients, outcome similar to the numerous nontransplant clinical trials of statins in atherosclerosis. In two recent in vitro studies, statins have been reported to repress induction of MHC-II by interferon-gamma and selectively block leukocyte function antigen-1, both of which decrease T-lymphocyte activation. In conclusion, statins appear to have outcome benefits in heart and kidney transplant patients; however, firm evidence for a clinical immunosuppressive effect is lacking. Further studies in humans will be needed to demonstrate this potential effect of statins. Overall, the outcome benefits of statins from the heart and kidney clinical studies provide a firm rationale to support the use of statins in organ transplantation.

Perillyl alcohol-mediated inhibition of lung cancer cell line proliferation: potential mechanisms for its chemotherapeutic effects

Perillyl alcohol (POH) is currently being tested in clinical trials as an anticancer agent, though its mechanism of action has not been definitively established. We treated two human lung cancer cell lines, H322 and H838, with POH to determine its antitumor properties. A sulforhodamine B (SRB) cell proliferation assay was used to determine the effects of POH after 1 and 5 days of treatment with 0.25, 0.5, 0.75, 1.0, and 1.5 mM POH. After 1 day of treatment, little difference could be seen between the lowest and highest concentrations of POH. However, after 5 days, both cell lines showed a dose-dependent decrease in cell proliferation that ranged from 15% to 83%. A clonogenic assay confirmed these results-while there was no significant effect of POH after 1 day of exposure, a dose-dependent decrease in colony formation, ranging from 15% to 100%, was seen after 5 days of treatment. Time-lapse video microscopy revealed that apoptotic cells were evident within 24-48 h of treatment with 1.5 mM POH. The appearance of apoptotic cells was preceded by increased caspase-3 activity and cleavage of poly (ADP-ribose) polymerase (PARP) as POH activated caspase-3 activity 3-6-fold. Nuclear staining with 4',6-diamidino-2-phenylindole (DAPI) confirmed the classical characteristics of apoptosis in POH-treated cells. DNA microarray expression analysis was performed following 8 and 24 (H322) or 8 and 48 (H838) h of treatment with 1.5 mM POH. While a large number of genes were up- or downregulated in the two cell lines at various times after POH treatment, the levels of expression of only eight genes were up- or down-related in both cell lines at both of the time points examined. The significance of these genes as potential mediators of POH action is still uncertain, but the limited number of commonly up- or downregulated genes detected by microarray expression analysis suggests that POH may mediate its effects via posttranscriptional mechanisms. Our results suggest that POH may have potential use as an anticancer drug that stimulates or sensitizes lung tumor cells to apoptosis, and this effect may depend on genetic lesions present in tumor cells.

Studies with cytotoxic agents suggest that apoptosis is not a major determinant of clonogenic death in neuroblastoma cells

We have previously reported the selection of a radioresistant human neuroblastoma cell line, Clone F, from IMR32 cells. We have shown that clonogenic radioresistance in these cells is accompanied by a reduced level of radiation-induced apoptosis [Cancer Res 55 (1995) 4915]. Here, we measured the response of these lines to several cytotoxic agents, in terms of clonogenicity and apoptosis. In the clonogenic assay, the radioresistant line was also resistant to cisplatin, melphalan and doxorubicin, but not to perillyl alcohol. However, all these agents produced less apoptosis in the Clone F cells, except cisplatin, which failed to induce any apoptosis in either cell line. Reduced apoptosis cannot be the cause of the Clone F cells' resistance to cisplatin. By extension, the Clone F cells' resistance to radiation and other agents cannot be due to diminished apoptosis either. Based on these results, apoptosis may not be a useful surrogate for clonogenic outcome.

Cytotoxicity of perillyl alcohol against cancer cells is potentiated by hyperthermia

PURPOSE

Perillyl alcohol (POH) (4-isopropenyl-cyclohexenecarbinol) is a member of the monoterpenes, which are present in various fruits and vegetables. POH has been demonstrated to be cytotoxic against a variety of experimental cancer cells in vitro and in vivo. Phase I clinical trials have indicated that POH may be useful for human tumor treatment. The purpose of our study was to reveal whether the anticancer effect of POH could be enhanced by hyperthermia.

METHODS AND MATERIALS

SCK mammary carcinoma cells of A/J mice were used. The effects of POH or hyperthermia alone were studied by incubating the cells during exponential growth phase in culture with 0.25-1.0 mM of POH at 37 degrees C for varying lengths of time or heating cells at 41-43 degrees C for varying lengths of time. The combined effect of POH and hyperthermia was investigated by heating the cells with 1 mM of POH at 41-43 degrees C for varying lengths of time. The effects of the treatments were evaluated using the clonogenic cell survival assay and three types of apoptosis assays.

RESULTS

An incubation of SCK cells with 1 mM of POH at 37 degrees C for 60 min or hyperthermia at 43 degrees C for 1 h decreased clonogenic cell survival to 40% and 60%, respectively. When the cells were heated at 43 degrees C for 1 h in the presence of 1 mM of POH, clonogenic cell survival decreased to 0.2%, indicating that hyperthermia potentiated the effect of POH to cause clonogenic cell death. Hyperthermia also markedly increased the degree of POH-induced apoptosis.

CONCLUSION

Hyperthermia synergistically potentiates the cytotoxicity of naturally occurring POH against cancer cells.

Statin use is associated with improved function and survival of lung allografts

3-Hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) are widely used antilipidemic agents that are also immunomodulatory. We evaluated possible effects of these agents after lung transplantation by comparing outcomes of 39 allograft recipients, who were prescribed statins for hyperlipidemia, with those of 161 contemporaneous control recipients who did not receive these drugs. Acute rejection (>or= Grade II) was less frequently found in the statin group (15.1 versus 25.6% of biopsies, p < 0.01). None of 15 recipients started on statins during postoperative Year 1 developed obliterative bronchiolitis, whereas the cumulative incidence of this complication among control subjects was 37% (p < 0.01). Total cellularity, as well as proportions of inflammatory neutrophils and lymphocytes, were significantly lower in bronchoalveolar lavages of statin recipients. Among double lung recipients, those taking statins had significantly better spirometry: FVC (80 +/- 2 versus 70 +/- 1%) and FEV1 (87 +/- 2 versus 70 +/- 1%), as percentages of predicted values, and absolute FEV1/FVC (83.4 +/- 1.2 versus 78.6 +/- 0.5) (all p < 0.01). The 6-year survival of recipients taking statins (91%) was much greater than that of control subjects (54%) (p < 0.01). These data suggest statin use may have substantial clinical benefits after pulmonary transplantation.

Farnesyltransferase inhibition: a novel method of immunomodulation

Farnesyltransferase inhibitors (FTIs) are anticancer compounds that inhibit Ras GTPases. Since Ras GTPases play key roles in T cell activation and function, we hypothesized that FTIs have immunomodulatory properties and are potential antirejection agents. An investigation was performed on a potent FTI to evaluate this hypothesis in the in vitro setting. The in vitro effects of the FTI A-228839 were evaluated. Lectin- or antigen presenting cell (APC)-induced lymphocyte proliferation in the presence of A-228839 was measured. The effects of A-228839 on 1E5 T cell polarity were assessed by microscopy. Intracellular calcium ([Ca(2+)](i)) kinetics of lectin-activated lymphocytes was monitored by flow cytometry. The effects of A-228839 on peripheral blood mononuclear cell (PBMC) cytokine production was assessed by a cytometric bead array method. Activation-induced apoptosis was measured with an annexin V staining assay.A-228839 inhibited lectin-induced proliferation (IC(50)=0.24+/-0.11 microM). The inhibitory effects of A-228839 on lectin induced lymphocyte proliferation were additive to those of CsA. A-228839 was more effective in inhibiting APC-induced T cell proliferation (IC(50)=0.10+/-0.09 microM). A-228839 significantly disrupted the polarized shape of 1E5 T cells at physiologic concentrations. A-228839 altered PBMC baseline [Ca(2+)](i) but did not affect [Ca(2+)](i) kinetics during lectin-induced lymphocyte activation. A-228839 inhibited lymphocyte Th1 cytokine production at submicromolar levels and promoted apoptosis in lectin-activated lymphocytes.A-228839 potently inhibits lymphocyte activation and function. Our results suggest that FTIs may represent a new class of clinically useful immunomodulatory agents. A-228839 has potent in vitro immunomodulatory properties that warrant in vivo evaluation as an antirejection agent.

Statins as immunosuppressive agents

BACKGROUND

Coronary artery disease in the transplanted heart, also known as cardiac allograft vasculopathy, is one of the major causes of mortality late after heart transplantation. This accelerated form of atherosclerosis also affects the donor organs of other transplant recipients including that of liver, kidney and lung. There are multiple immune and non-immune risk factors associated with this disease process, one of which is hyperlipidemia. Use of lipid lowering agents, specifically HMG-CoA reductase inhibitors (statins) was initially reported to have outcomes benefit and possibly immunosuppressive effects in a single center study of heart transplant recipients. Other subsequent studies have supported this beneficial effect.

METHOD AND RESULTS

In a recent paper by Kwak and colleagues, the specific mechanism for this immunosuppressive effect has been elucidated through the use of experiments monitoring cell surface expression assayed by fluorescence-activated cell sorting and by immunofluorescence as well as mRNA levels of major histocompatibility complex class II (MHC-II). They report that statins repress induction of MHC-II by interferon-gamma and that this in turn represses activation of T-lymphocytes and other cell types including primary human smooth muscle cells and fibroblasts, as well as in established cell lines such as ThP1, melanomas, and HeLa cells.

CONCLUSION

In addition to previous clinical and laboratory publications this work by Kwak and colleagues has provided a firm scientific rationale to support the use of statins as adjunct immunosuppressive agents in organ transplantation.