Synthesis, Structure and Cytotoxic Properties of Copper(II) Complexes of 2-Iminocoumarins Bearing a 1,3,5-Triazine or Benzoxazole/Benzothiazole Moiety.

A series of copper(II) complexes of 2-imino-2H-chromen-3-yl-1,3,5-triazines 2a-h, 3-(benzoxazol-2-yl)-2H-chromen-2-imines 4a-b, and 3-(benzothiazol-2-yl)-2H-chromen-2-imines 6a-c were obtained by reacting of appropriate 2-iminocoumarin ligands L1a-h, L3a-b, and L5a-c with 3-fold molar excess of copper(II) chloride. The structure of these compounds was confirmed by IR spectroscopy, elemental analysis, and single-crystal X-ray diffraction data (2f, 2g, 2h, and 6c). All the synthesized complexes were screened for their activity against five human cancer cell lines: DAN-G, A-427, LCLC-103H, SISO, and RT-4 by using a crystal violet microtiter plate assay and relationships between structure and in vitro cytotoxic activity are discussed. The coordination of 2-iminocoumarins with copper(II) ions resulted in complexes 2a-h, 4a-b, and 6a-c with significant inhibitory properties toward tested tumor cell lines with IC50 values ranging from 0.04 µM to 15.66 µM. In comparison to the free ligands L1a-h, L3a-b, and L5a-c, the newly prepared Cu(II) complexes often displayed increased activity. In the series of copper(II) complexes of 2-imino-2H-chromen-3-yl-1,3,5-triazines 2a-h the most potent compound 2g contained a 4-phenylpiperazine moiety at position 6 of the 1,3,5-triazine ring and an electron-donating diethylamino group at position 7' of the 2-iminocoumarin scaffold. Among the Cu(II) complexes of 3-(benzoxazol-2-yl)-2H-chromen-2-imines 4a-b and 3-(benzothiazol-2-yl)-2H-chromen-2-imines 6a-c the most active was benzoxazole-2-iminocoumarin 4b that also possessed a diethylamino group at position 7' of the 2-iminocoumarin moiety. Moreover, compound 4b was found to be the most prominent agent and displayed the higher potency than cisplatin against tested cell lines.

Anti-PD-1 antibody increases NK cell cytotoxicity towards nasopharyngeal carcinoma cells in the context of chemotherapy-induced upregulation of PD-1 and PD-L1.

BACKGROUND: Nasopharyngeal carcinoma (NPC) is a highly malignant epithelial cancer linked to Epstein-Barr virus (EBV) infection. Tumors are characterized by a lymphomononuclear infiltrate and the number of natural killer (NK) cells in tumors appears to be of prognostic significance. Standard treatment for NPC in adolescents and young adults consists of induction chemotherapy followed by radiochemotherapy. Though survival rates are above 80%, the majority of patients suffer from long-term side-effects, mainly related to radiotherapy. The addition of immunotherapy to induction chemotherapy could improve tumor response. METHODS: We have investigated the killing of NPC cells by NK cells in the context of chemotherapy, using a panel of three nasopharyngeal carcinoma cell lines and a patient-derived xenograft. Cytotoxicity was measured using the calcein-release assay, while the contribution of different checkpoints and signaling pathways to killing was studied by siRNA-mediated gene silencing and chemical inhibitors. RESULTS: Chemotherapeutics cisplatin, 5-fluorouracil and gemcitabine sensitized NPC cells to killing by NK cells. Chemotherapeutics led to upregulation of PD-1 in NK cells and PD-L1 in NPC cells via NF-κB. Inhibition of the PD-L1/PD-1 checkpoint by an anti-PD-1 antibody or siRNA increased NK-cell cytotoxicity towards NPC cells. CONCLUSION: The addition of an anti-PD-1 antibody to chemotherapy in patients with NPC could increase the efficacy of induction chemotherapy. If confirmed in a clinical trial, more efficient induction therapy could allow the dose of radiotherapy to be reduced and thereby diminish severe late effects of such therapy.

Interferon beta increases NK cell cytotoxicity against tumor cells in patients with nasopharyngeal carcinoma via tumor necrosis factor apoptosis-inducing ligand.

BACKGROUND: Nasopharyngeal carcinoma (NPC) is an EBV-associated neoplasm occurring endemically in Southeast Asia and sporadically all over the world. In children and adolescents, high cure rates have been obtained using chemotherapy, radiochemotherapy and maintenance therapy with interferon beta (IFNß). The mechanism by which IFNß contributes to a low systemic relapse rate has not yet been fully revealed. PATIENTS AND METHODS: NK cells and serum samples from two patients with NPC were analyzed before and at different time points during IFNß therapy, for assessment of TRAIL expression and NK cell cytotoxicity. Cytotoxicity was measured using the calcein release assay and the contribution of different death effector pathways was analyzed using specific inhibitors. RESULTS: Treatment with IFNß induced TRAIL expression on patients' NK cells and increased their cytotoxicity against NPC targets in vitro. NK cell-mediated cytotoxicity was predominately mediated via TRAIL. IFNß also induced the production of soluble TRAIL (sTRAIL) by NK cells and its release upon contact with NPC cells. IFNß treatment increased serum levels of sTRAIL in patients. Moreover, sTRAIL concentrated from patients' serum samples induced apoptosis ex vivo in NPC cells from a patient-derived xenograft. CONCLUSION: Increased cytotoxicity of NK cells against NPC cells and increased serum levels of biologically active TRAIL in patients treated with IFNß could be a means to eliminate micrometastatic disease and explain the low systemic relapse rate in this patient group.

Hybrid Molecules Composed of 2,4-Diamino-1,3,5-triazines and 2-Imino-Coumarins and Coumarins. Synthesis and Cytotoxic Properties.

A series of 2-imino-2H-chromen-3-yl-1,3,5-triazine compounds 5⁻12, which are namely hybrids of 2,4-diamino-1,3,5-triazines and 2-imino-coumarins, was synthesized by reacting 2-(4,6-diamine-1,3,5-triazin-2-yl)acetonitriles 1⁻4 with 2-hydroxybenzaldehydes. After this, upon heating in aqueous DMF, 2-imino-2H-chromen-3-yl-1,3,5-triazines 10 and 12 were converted into the corresponding 2H-chromen-3-yl-1,3,5-triazines 13 and 14, which are essentially hybrids of 2,4-diamino-1,3,5-triazines and coumarins. The in vitro anticancer activity of the newly prepared compounds was evaluated against five human cancer cell lines: DAN-G, A-427, LCLC-103H, SISO and RT-4. The greatest cytotoxic activity displayed 4-[7-(diethylamino)-2-imino-2H-chromen-3-yl]-6-(4-phenylpiperazin-1-yl)-1,3,5-triazin-2-amine (11, IC50 in the range of 1.51⁻2.60 µM).

PDE4 inhibition reduces neointima formation and inhibits VCAM-1 expression and histone methylation in an Epac-dependent manner.

Phosphodiesterase 4 (PDE4) activity mediates cAMP-dependent smooth muscle cell (SMC) activation following vascular injury. In this study we have investigated the effects of specific PDE4 inhibition with roflumilast on SMC proliferation and inflammatory activation in vitro and neointima formation following guide wire-induced injury of the femoral artery in mice in vivo. In vitro, roflumilast did not affect SMC proliferation, but diminished TNF-α induced expression of the vascular cell adhesion molecule 1 (VCAM-1). Specific activation of the cAMP effector Epac, but not PKA activation mimicked the effects of roflumilast on VCAM-1 expression. Consistently, the reduction of VCAM-1 expression was rescued following inhibition of Epac. TNF-α induced NFκB p65 translocation and VCAM-1 promoter activity were not altered by roflumilast in SMCs. However, roflumilast treatment and Epac activation repressed the induction of the activating epigenetic histone mark H3K4me2 at the VCAM-1 promoter, while PKA activation showed no effect. Furthermore, HDAC inhibition blocked the inhibitory effect of roflumilast on VCAM-1 expression. Both, roflumilast and Epac activation reduced monocyte adhesion to SMCs in vitro. Finally, roflumilast treatment attenuated femoral artery intima-media ratio by more than 50% after 4weeks. In summary, PDE4 inhibition regulates VCAM-1 through a novel Epac-dependent mechanism, which involves regulatory epigenetic components and reduces neointima formation following vascular injury. PDE4 inhibition and Epac activation might represent novel approaches for the treatment of vascular diseases, including atherosclerosis and in-stent restenosis.

IL6 secreted by Ewing sarcoma tumor microenvironment confers anti-apoptotic and cell-disseminating paracrine responses in Ewing sarcoma cells.

BACKGROUND: The prognosis of patients with Ewing sarcoma (ES) has improved over the course of the last decades. However, those patients suffering from metastatic and recurrent ES still have only poor chances of survival and require new therapeutic approaches. Interleukin-6 (IL6) is a pleiotropic cytokine expressed by immune cells and a great variety of cancer cells. It induces inflammatory responses, enhances proliferation and inhibits apoptosis in cancer cells, thereby promoting chemoresistance. METHODS: We investigated expression of IL6, its receptors and the IL6 signal transduction pathway in ES tumor samples and cell lines applying reverse transcriptase PCR, immunoblot and immunohistochemistry. The impact of IL6 on cell viability and apoptosis in ES cell lines was analyzed by MTT and propidium iodide staining, migration assessed by chorioallantoic membrane (CAM) assay. RESULTS: Immunohistochemistry proved IL6 expression in the stroma of ES tumor samples. IL6 receptor subunits IL6R and IL6ST were expressed on the surface of ES cells. Treatment of ES cells with rhIL6 resulted in phosphorylation of STAT3. rhIL6 protected ES cells from serum starvation-induced apoptosis and promoted migration. IL6 blood serum levels were elevated in a subgroup of ES patients with poor prognosis. CONCLUSIONS: These data suggest that IL6 contributes to ES tumor progression by increasing resistance to apoptosis in conditions of cellular stress, such as serum starvation, and by promotion of metastasis.

Structural diversity of copper(II) complexes with N-(2-pyridyl)imidazolidin-2-ones(thiones) and their in vitro antitumor activity.

Six series of structurally different mono- and binuclear copper(II) complexes 5-10 were obtained by reacting N-(2-pyridyl)imidazolidin-2-ones (1a-l), N,N'-bis(2-pyridyl)imidazolidin-2-ones (2a,b), N-acyl-N'(2-pyridyl)imidazolodin-2-ones (3a-j) and N-(2-pyridyl)imidazolidine-2-thiones (4a-g) with copper(II) chloride at an ambient temperature. The coordination modes of the complexes obtained were established by elemental analysis, IR spectroscopic data and single crystal X-ray diffraction studies. The in vitro cytotoxic activities of both the free ligands and copper(II) complexes were evaluated using a crystal violet microtiter plate assay on five human tumor cell lines: LCLC-103H, A-427, SISO, RT-4 and DAN-G. The free ligands 1-4 at concentration attainable in cancer cells of 20 µM showed no meaningful cytotoxic effect with cell viability in the range of 88%-100%. The most potent copper(II) complex of 1-(6-ethoxy-2-pyridyl)imidazolidin-2-one (6b) exhibited selective cytotoxicity against A-427 lung cancer cell line, while the complexes of 1-(5-methyl-2-pyridyl)imidazolidine-2-thione (5h) and 1-(4-tert-butyl-2-pyridyl)imidazolidine-2-thione (5j) showed cytostatic effect against a whole panel of five human tumor cell lines. In conclusion, the only complexes that showed remarkably increased activity in comparison to the free ligands were those obtained from N-(2-pyridyl)imidazolidine-2-thiones 4c and 4e substituted with alkyl group at position 4 or 5 of pyridine ring.

Nasopharyngeal Carcinoma Cell Lines: Reliable Alternatives to Primary Nasopharyngeal Cells?

Nasopharyngeal carcinoma (NPC) is a type of cancer that originates from the mucosal lining of the nasopharynx and can invade and spread. Although contemporary chemoradiotherapy effectively manages the disease locally, there are still challenges with locoregional recurrence and distant failure. Therefore, it is crucial to have a deeper understanding of the molecular basis of NPC cell movement in order to develop a more effective treatment and to improve patient survival rates. Cancer cell line models are invaluable in studying health and disease and it is not surprising that they play a critical role in NPC research. Consequently, scientists have established around 80 immortalized human NPC lines that are commonly used as in vitro models. However, over the years, it has been observed that many cell lines are misidentified or contaminated by other cells. This cross-contamination leads to the creation of false cell lines that no longer match the original donor. In this commentary, we discuss the impact of misidentified NPC cell lines on the scientific literature. We found 1159 articles from 2000 to 2023 that used NPC cell lines contaminated with HeLa cells. Alarmingly, the number of publications and citations using these contaminated cell lines continued to increase, even after information about the contamination was officially published. These articles were most commonly published in the fields of oncology, pharmacology, and experimental medicine research. These findings highlight the importance of science policy and support the need for journals to require authentication testing before publication.

Multimodal Treatment of Nasopharyngeal Carcinoma in Children, Adolescents and Young Adults-Extended Follow-Up of the NPC-2003-GPOH Study Cohort and Patients of the Interim Cohort.

Nasopharyngeal carcinoma (NPC) in children and young adults has been treated within two consecutive prospective trials in Germany, the NPC-91 and the NPC-2003 study of the German Society of Pediatric Oncology and Hematology (GPOH). In these studies, multimodal treatment with induction chemotherapy, followed by radio (chemo)therapy and interferon-beta maintenance, yielded promising survival rates even after adapting total radiation doses to tumor response. The outcome of 45 patients in the NPC-2003 study was reassessed after a median follow-up of 85 months. In addition, we analyzed 21 further patients after closure of the NPC-2003 study, recruited between 2011 and 2017, and treated as per the NPC-2003 study protocol. The EFS and OS of 66 patients with locoregionally advanced NPC were 93.6% and 96.7%, respectively, after a median follow-up of 73 months. Seven patients with CR after induction therapy received a reduced radiation dose of 54 Gy; none relapsed. In young patients with advanced locoregional NPC, excellent long-term survival rates can be achieved by multimodal treatment, including interferon-beta. Radiation doses may be reduced in patients with complete remission after induction chemotherapy and may limit radiogenic late effects.

Radiotherapy Combined with PD-1 Inhibition Increases NK Cell Cytotoxicity towards Nasopharyngeal Carcinoma Cells.

BACKGROUND: Nasopharyngeal carcinoma (NPC) in endemic regions and younger patients is characterized by a prominent lymphomononuclear infiltration. Radiation is the principal therapeutic modality for patients with NPC. Recent data suggest that the efficacy of radiotherapy in various cancers can be augmented when combined with immune checkpoint blockade. Here, we investigate the effect of radiotherapy on the killing of NPC cells by Natural Killer (NK) cells. METHODS: NPC cell lines and a patient-derived xenograft were exposed to NK cells in the context of radiotherapy. Cytotoxicity was measured using the calcein-release assay. The contribution of the PD-L1/PD-1 checkpoint and signaling pathways to killing were analyzed using specific inhibitors. RESULTS: Radiotherapy sensitized NPC cells to NK cell killing and upregulated expression of PD-1 ligand (PD-L1) in NPC cells and PD-1 receptor (PD-1) in NK cells. Blocking of the PD-L1/PD-1 checkpoint further increased the killing of NPC cells by NK cells in the context of radiotherapy. CONCLUSION: Radiation boosts the killing of NPC cells by NK cells. Killing can be further augmented by blockade of the PD-L1/PD-1 checkpoint. The combination of radiotherapy with PD-L1/PD-1 checkpoint blockade could therefore increase the efficacy of radiotherapy in NPC tumors.

Inhibition of nitric oxide synthases prevents and reverses alpha,beta-meATP-induced neck muscle nociception in mice.

INTRODUCTION: Tension-type headache (TTH) is associated with noxious input from neck muscles. Intravenous administration of the unspecific nitric oxide synthase inhibitor L-NMMA in chronic TTH patients caused analgesia and reduction of neck muscle tenderness. METHODS: The unspecific nitric oxide synthase inhibitor L-NMMA was applied in an experimental model for neck muscle nociception in anesthetized mice (N = 25). RESULTS: Local injection of α,ß-meATP into semispinal neck muscles induced sustained facilitation of brainstem nociception as monitored by the jaw-opening reflex. Preceding intraperitoneal administration of L-NMMA (0.05, 0.1, 1 mg/kg) prevented reflex facilitation evoked by α,ß-meATP in a dose-dependent manner. Intraperitoneal injection of L-NMMA subsequent to intramuscular α,ß-meATP application reversed established brainstem reflex facilitation back to baseline values. DISCUSSION: Both experiments with preceding and subsequent L-NMMA indicate the involvement of nitric oxide synthases in the induction and maintenance of facilitation. However, future experiments will have to address the involvement of various isoenzymes in order to provide for new therapeutic concepts in TTH.

Insulinoma in a patient with MEN 1 syndrome--9-year follow-up: case report.

INTRODUCTION: Multiple endocrine neoplasia type 1 (MEN 1) is a rare autosomal dominant inherited endocrine disease characterized by pancreatic, parathyroid, and anterior pituitary tumours. Hypercalcaemia due to parathyroid tumours is usually the first manifestation of MEN 1. Pancreatic islet tumours occur less frequently, among them gastrinomas and insulinomas are the most prevalent. Prolactinomas are a relatively common pituitary presentation of the syndrome. The gene causing MEN 1 is localized in chromosome 11q13 and encodes a protein named menin, which interacts with various proteins involved in transcriptional regulation, cell division, and DNA repair. Various mutations in the menin gene have been described, but so far no strong correlation between genotype and phenotype has been found. CASE REPORT: We report a case of a 31-year-old man, a lawyer, who was diagnosed with MEN 1 syndrome in 1999 at the age of 21 when he was operated because of prolactinoma and hyperparathyroidism. In 2000 insulinoma was suspected and eventually multifocal lesions in the pancreas were revealed. However, the patient did not agree to be operated on. Since then he has been followed up and has been treated with diazoxid. We observed gradual progression of the disease, but the patient remains in relatively good condition. CONCLUSIONS: Careful screening for MEN 1 is important in young patients with pituitary tumours. Regular follow up is crucial even after surgical treatment. The presented patient developed gradual enlargement of insulinomas and reoccurrence of hyperparathyroidism as well.

Emerging therapeutic targets for nasopharyngeal carcinoma: opportunities and challenges.

Introduction: Nasopharyngeal carcinoma (NPC) is a major public health problem in several countries, especially those in Southeast Asia and North Africa. In its typical poorly differentiated form, the Epstein-Barr virus (EBV) genome is present in the nuclei of all malignant cells with restricted expression of a few viral genes. The malignant phenotype of NPC cells results from the influence of these viral products in combination with cellular genetic, epigenetic and functional alterations. With regard to host/tumor interactions, NPC is a remarkable example of immune escape in the context of a hot tumor.Areas covered: This article has an emphasis on emerging therapeutic targets that are considered upstream or at an early stage of clinical application. It examines targets related to cellular oncogenic alterations, latent EBV infection and tumor interactions with the immune system.Expert opinion: There is a remarkable emergence of new agents that target EBV products. The clinical application of these agents would benefit from a systematic and comprehensive molecular classification of NPCs and from easy access to pre-clinical models in public repositories. There is a strong rationale for more investigations on the potential of immune modulators, especially those related to NK cells.

Interferon ß and Anti-PD-1/PD-L1 Checkpoint Blockade Cooperate in NK Cell-Mediated Killing of Nasopharyngeal Carcinoma Cells.

Nasopharyngeal carcinoma (NPC) is a highly malignant epithelial cancer linked to EBV infection. Addition of interferon-ß (IFNß) to chemo- and radiochemotherapy has led to survival rates >90% in children and adolescents. As NPC cells are sensitive to apoptosis via tumor necrosis factor-related apoptosis inducing ligand (TRAIL), we explored the role of TRAIL and IFNß in the killing of NPC cells by natural killer (NK) cells. NPC cells, including cells of a patient-derived xenograft were exposed to NK cells in the presence or absence of IFNß. NK cells killed NPC- but not nasoepithelial cells and killing was predominately mediated via TRAIL. Incubation of NK cells with IFNß increased cytotoxicity against NPC cells. Concomitant incubation of NK- and NPC cells with IFNß before coculture reduced cytotoxicity and could be overcome by blocking the PD-1/PD-L1 axis leading to the release of intracellular TRAIL from NK cells. In conclusion, combination of IFNß and anti-PD-1, augmenting cytotoxicity of NK cells against NPC cells, could be a strategy to improve NPC-directed therapy and warrants further evaluation in vivo.

Interferon beta induces apoptosis in nasopharyngeal carcinoma cells via the TRAIL-signaling pathway.

The combination of neoadjuvant chemotherapy, radiochemotherapy, and maintenance therapy with interferon beta (IFNß) has led to superior results in the treatment of children and adolescents with nasopharyngeal carcinoma (NPC). However, nothing is known about the mechanism of the antitumor activity of IFNß in NPC. Here, we investigate the role of IFNß on apoptosis in NPC cells. Six NPC cell lines, one patient-derived NPC xenograft (PDX) and one SV40-transformed nasoepithelial cell line were used. Induction of apoptosis by IFNß was measured by flow cytometric analysis of subG1-DNA-content, Hoechst 33258 staining and activation of caspase-3. Dissection of death ligand signaling pathways included measuring surface expression of its components by flow cytometry, activation by death ligands and neutralization with specific antibodies and siRNA. IFNß induced apoptosis at concentrations achievable in humans in five of six NPC cell lines and in PDX cells but not in nasoepithelial cells. Inhibition of caspases-3 and -8 abrogated this effect suggesting IFNß promoted apoptosis through the extrinsic pathway. IFNß induced surface expression of TRAIL and TRAIL-R2 and the addition of an anti-TRAIL-antibody or transfection with TRAIL-siRNA blocked IFNß-induced apoptosis. No induction of TRAIL-expression was noted in the IFNß-resistant cell line. In conclusion, IFNß leads to apoptosis in NPC cells in an autocrine way via the induction of TRAIL expression and subsequent activation of the TRAIL-signaling pathway. The mechanism described could at least partly explain the clinical benefit of IFNß in the treatment of NPC. Further studies in a mouse-xenograft model are warranted to substantiate this effect in vivo.

Reduced circulating CD4+CD25+ cell populations in Guillain-Barré syndrome.

Guillain-Barré syndrome (GBS) is a monophasic inflammatory disease considered to be due to autoimmunity. In order to test the hypothesis that the disease is associated with a perturbation of the circulating lymphoid cell population, we tested the mononuclear cells from the venous blood of 21 patients with Guillain-Barré syndrome (GBS) and 20 healthy controls by flow cytometry. The proportions and numbers of B and T lymphocytes, and CD4, CD8, double negative and gammadelta T cell subsets and numbers of monocytes were not significantly different in the patients compared with the controls. However, the number and proportion of CD4+CD25+ cells were reduced in acute GBS (mean number 61.7 cells/microl, 95% CI 42.9-80.4 and mean percentage 4.6%, 95% CI 3.8-5.4) compared with controls (mean number 99.8 cells/microl, 95% CI 74.7-124.9, p=0.02, and mean percentage 6.0%, 95% CI 4.9-7.1%, p=0.037). In addition, in GBS patients, the number and proportion of CD4+ T cells expressing CD25+ and HLA-DP, DQ, DR (mean number 11.9 cells/microl, 95% CI 7.6-16.1 and mean percentage 0.8%, 95% CI 0.5-1.1%) was lower than in healthy controls (23.5 cells/microl, 95% CI 16.4-30.6, p=0.01, and mean percentage 1.4%, 95% CI 1.1-1.8%, p=0.005. Since CD4+CD25+ cells include cells with special immunoregulatory functions, further investigation of this phenomenon and its relation to possible loss of regulatory T cell function in GBS is warranted.

(18)O/(16)O isotope effect on miscibility of isobutyric acid with water.

The miscibility of isobutyric acid with water and the influence of the isotope substitution of oxygen (16O/18O) in water over a broad concentration range are reported. The system exhibits a phase diagram with an upper critical solution temperature (UCST) and a visible isotope effect thereon. The oxygen isotope substitution decreases the UCST, leading to better miscibility of isobutyric acid with water. The isotope shift, DeltaTc = Tc(18O) - Tc(16O), extrapolated to the 100% enrichment in 18O, is equal to -1.15 K; hence it is much smaller and opposite to that found for deuterium substitution. The origin of the observed miscibility isotope effect has been qualitatively discussed in terms of the condensed-phase isotope effect theory.

Isotope effects on miscibility of 1-butyl-3-methylimidazolium tetrafluoroborate with butanols.

The liquid-liquid miscibility temperatures as a function of composition and deuterium substitution have been experimentally determined for the binary mixtures of 1-butyl-3-methylimidazolium tetrafluroborate with 1-butanol, isobutyl alcohol, 2-butanol, and tert-butyl alcohol and their deuterated forms (OH/OD substitution). All systems exhibit upper critical solution temperatures (UCSTs) with a visible effect of branching in alcohols. Deuteration of alcohols in the hydroxyl group results in a decrease of the UCST of the given system and the largest shift is observed for tert-butyl alcohol. These solvent isotope effects nicely correlate with the polarity expressed by dielectric constants or E(T)(30) parameters of alcohols. The effect of the isotope substitution on the miscibility of ILs with butanols can be rationalized by using the statistical-mechanical theory of the isotope effects coupled with a phenomenological g(E) model. Following this procedure one finds that the isotope shift of UCST is associated mainly with the zero-point energy contribution.