Isobolographic analysis of interaction between drugs with nonparallel dose-response relationship curves: a practical application

Antiproliferative effects of LY-2183240 combined with various chemotherapeutic drugs in an isobolographic in vitro model of malignant melanoma

Despite a great progress in identifying treatment options for patients with malignant melanoma, novel therapies tend to be costly and, in some cases, produce adverse effects forcing the melanoma patients to withdraw drugs. There is a strong need for less expensive drugs with a more favorable spectrum of anticancer actions. This study was designed to assess whether LY-2183240 (a potent inhibitor of both, anandamide cellular reuptake and fatty acid amide hydrolase (FAAH), an enzyme that degrades anandamide) has antiproliferative and cytotoxic effects on various human malignant melanoma cell lines (primary A375 and FM55P, metastatic SK-MEL28 and FM55M2) when administered alone or in combination with docetaxel, paclitaxel, mitoxantrone and cisplatin via the MTT assay. The MTT, LDH and BrdU assays were used to evaluate the potency and safety of LY-2183240, whereas isobolographic analysis of interactions was applied to characterize the interactions of LY-2183240 with the studied chemotherapeutics (docetaxel, paclitaxel, mitoxantrone and cisplatin). The isobolography confirmed that the combinations of LY-2183240 with docetaxel, paclitaxel and mitoxantrone produced additive interactions in all the tested melanoma cell lines. Only two antagonistic interactions for LY-2183240 combined with cisplatin in the A375 and FM55P cell lines were observed by the MTT assay. In conclusion, LY-2183240 can be considered an add-on drug for the treatment of melanoma, when combined with docetaxel, paclitaxel, or mitoxantrone, but not with cisplatin.

AM1172 (a hydrolysis-resistant endocannabinoid analog that inhibits anandamide cellular uptake) reduces the viability of the various melanoma cells, but it exerts significant cytotoxic effects on healthy cells: an in vitro study based on isobolographic analysis

BACKGROUND

Despite great advances in our understanding of the impact of cannabinoids on human organism, many of their properties still remain undetermined, including their potential antineoplastic effects. This study was designed to assess the anti-proliferative and cytotoxic effects of AM1172 (a hydrolysis-resistant endocannabinoid analog that inhibits anandamide cellular uptake) administered alone and in combinations with docetaxel (DOCX), paclitaxel (PACX), mitoxantrone (MTX) and cisplatin (CDDP) on various human malignant melanoma A375, FM55P, SK-MEL 28 and FM55M2 cell lines.

MATERIALS

In the MTT, LDH, and BrdU assays, the potency and safety of AM1172 when administered alone and in combinations with DOCX, PACX, MTX, and CDDP were determined.

RESULTS

The isobolographic analysis revealed that combinations of AM1172 with PACX, DOCX, MTX, and CDDP exerted additive interactions, except for a combination of AM1172 with PACX in primary melanoma A375 cell line, for which synergy was observed (*p<0.05). Nevertheless, AM1172 when administered alone produced cytotoxic effects on healthy human melanocytes (HEMa-LP) and human keratinocytes (HaCaT), which unfortunately limits its potential therapeutic utility.

CONCLUSIONS

AM1172 cannot be used separately as a chemotherapeutic drug, but it can be combined with PACX, DOCX, MTX, and CDDP, offering additive interactions in terms of the anti-proliferative effects in various malignant melanoma cell lines.

Heterogeneous Cellular Response of Primary and Metastatic Human Gastric Adenocarcinoma Cell Lines to Magnoflorine and Its Additive Interaction with Docetaxel

Gastric cancer is the most common cancer and remains the leading cause of cancer death worldwide. In this study, the anticancer action of magnoflorine isolated via counter-current chromatography from the methanolic extract of Berberis vulgaris root against gastric cancer in models of primary ACC-201 and AGS and metastatic MKN-74 and NCI-N87 cell lines was analyzed. Cell viability and proliferation were tested through the use of MTT and BrdU tests, respectively. Cell cycle progression and apoptosis were evaluated using flow cytometry. The interaction of magnoflorine and docetaxel has been examined through isobolographic analysis. Moreover, potential toxicity was verified in zebrafish in an in vivo model. Gastric cancer cell lines revealed different responses to magnoflorine treatment with regard to viability/proliferation, apoptosis induction and cell cycle inhibition without any undesirable changes in the development of larval zebrafish at the tested concentrations. What is more, magnoflorine in combination with docetaxel produced an additive pharmacological interaction in all studied gastric cancer cell lines, which may suggest a complementary mechanism of action of both compounds. Taken together, these findings provide a foundation for the possibility of magnoflorine as a potential therapeutic approach for gastric cancer and merits further investigation, which may pave the way for clinical uses of magnoflorine.

Daphnetin, a Coumarin with Anticancer Potential against Human Melanoma: In Vitro Study of Its Effective Combination with Selected Cytostatic Drugs

(1) The treatment of metastatic or drug-resistant melanoma is still a significant therapeutic problem. The aim of this study was to evaluate the anticancer potential of daphnetin (7,8-dihydroxycoumarin) and its combinations with five different cytostatic drugs (mitoxantrone, docetaxel, vemurafenib, epirubicin and cisplatin). (2) The viability, proliferation and cytotoxicity of daphnetin against four human malignant melanoma cell lines were evaluated. The interactions were assessed using isobolographic analysis for the combinations of daphnetin with each of the five cytostatic drugs. (3) Daphnetin showed anticancer activity against malignant melanoma, with IC₅₀ values ranging from 40.48 ± 10.90 µM to 183.97 ± 18.82 µM, depending on the cell line. The combination of daphnetin with either vemurafenib or epirubicin showed an antagonistic interaction. Moreover, additive interactions were observed for the combinations of daphnetin with cisplatin and docetaxel. The most desirable synergistic interactions for human melanoma metastatic cell lines were observed for the combination of daphnetin with mitoxantrone. (4) The obtained results suggest that daphnetin should not be combined with vemurafenib or epirubicin in the treatment of malignant melanoma due to the abolition of their anticancer effects. The combination of daphnetin with mitoxantrone is beneficial in the treatment of metastatic melanoma due to their synergistic interaction.

Synergy, Additivity and Antagonism between Esculetin and Six Commonly Used Chemotherapeutics in Various Malignant Melanoma Cell Lines-An Isobolographic Analysis

(1) Malignant melanomas are dangerous skin cancers, and the treatment of melanomas with various cytostatic drugs often causes side effects and after their prolonged use resistance to these drugs appears. The aim of this study was to evaluate the anticancer effects of esculetin (a simple coumarin) and to assess pharmacodynamic interactions between esculetin and six commonly used cytostatic drugs (cisplatin, epirubicin, docetaxel, paclitaxel, mitoxantrone and vemurafenib) using an isobolographic analysis. (2) The experiments were carried out on four human malignant melanoma cell lines (FM55P, A375, FM55M2 and SK-MEL28). The effects of esculetin on viability, cell proliferation and cytotoxicity were verified in the range of concentrations of 2-200 μM. (3) Esculetin inhibited, in a dose-dependent manner, malignant melanoma cell viability and proliferation. The IC₅₀ for esculetin ranged from 18.20 ± 2.93 to 120.64 ± 30.39 μM depending on the melanoma cell lines used. The combinations of esculetin with epirubicin and vemurafenib showed antagonistic interactions, the combinations of esculetin with cisplatin, docetaxel and paclitaxel showed additive interactions. For the combinations of esculetin with mitoxantrone, the isobolographic analysis displayed synergy. (4) In the treatment of malignant melanoma, esculetin should not be combined with epirubicin or vemurafenib, due to the reduction of their anticancer effects, while the synergistic interactions (esculetin + mitoxantrone) deserve a preclinical recommendation as a beneficial combination during anticancer therapy.

Fraxetin Interacts Additively with Cisplatin and Mitoxantrone, Antagonistically with Docetaxel in Various Human Melanoma Cell Lines-An Isobolographic Analysis

Malignant melanoma is a skin cancer characterized by rapid development, poor prognosis and high mortality. Due to the frequent drug resistance and/or early metastases in melanoma, new therapeutic methods are urgently needed. The study aimed at assessing the cytotoxic and antiproliferative effects of scoparone and fraxetin in vitro, when used alone and in combination with three cytostatics: cisplatin, mitoxantrone, and docetaxel in four human melanoma cell lines. Our experiments showed that scoparone in the concentration range tested up to 200 µM had no significant effect on the viability of human malignant melanoma (therefore, it was not possible to evaluate it in combination with other cytostatics), while fraxetin inhibited cell proliferation with IC₅₀ doses in the range of 32.42-73.16 µM, depending on the cell line. Isobolographic analysis allowed for the assessment of the interactions between the studied compounds. Importantly, fraxetin was not cytotoxic to normal keratinocytes (HaCaT) and melanocytes (HEMa-LP), although it slightly inhibited their viability at high concentrations. The combination of fraxetin with cisplatin and mitoxantrone showed the additive interaction, which seems to be a promising direction in melanoma therapy. Unfortunately, the combination of fraxetin with docetaxel may not be beneficial due to the antagonistic antiproliferative effect of both drugs used in the mixture.

Comparison of the Anticancer Effects of Arvanil and Olvanil When Combined with Cisplatin and Mitoxantrone in Various Melanoma Cell Lines-An Isobolographic Analysis

Due to the unique structures of arvanil and olvanil, the drugs combine certain properties of both cannabinoids and vanilloids, which makes them able to stimulate both TPRV1 and CB1 receptors and causes them to be interesting agents in the setting of carcinoma treatment. The aim of this study was to investigate the cytotoxic and anti-proliferative effects of arvanil and olvanil when administered alone and in combination with cisplatin (CDDP) and mitoxantrone (MTX), using various primary (A375, FM55P) and metastatic (SK-MEL 28, FM55M2) human malignant melanoma cell lines. The results indicate that both arvanil and olvanil inhibited (dose-dependently) the viability and proliferation of various malignant melanoma cells, as demonstrated by MTT and BrdU assays. The safety profile of both arvanil and olvanil tested in human keratinocytes (HaCaT) and normal human melanocytes (HEMa-LP) revealed that neither arvanil nor olvanil caused significant cytotoxicity in HaCaT and HEMa-LP cell lines in LDH and MTT assays. Isobolographically, it was found that both arvanil and olvanil exerted additive interactions with MTX and antagonistic interactions with CDDP in the studied malignant melanoma cell lines. In conclusion, the combinations of arvanil or olvanil with MTX may be considered as a part of melanoma multi-drug therapy; however, the combination of these compounds with CDDP should be carefully considered due to the antagonistic interactions observed in the studied malignant melanoma cell lines.

Isoquinoline Alkaloids from Coptis chinensis Franch: Focus on Coptisine as a Potential Therapeutic Candidate against Gastric Cancer Cells

Gastric cancer (GC) has high incidence rates and constitutes a common cause of cancer mortality. Despite advances in treatment, GC remains a challenge in cancer therapy which is why novel treatment strategies are needed. The interest in natural compounds has increased significantly in recent years because of their numerous biological activities, including anti-cancer action. The isolation of the bioactive compounds from Coptis chinensis Franch was carried out with the Centrifugal Partition Chromatography (CPC) technique, using a biphasic solvent system composed of chloroform (CHCl₃)—methanol (MeOH)—water (H₂O) (4:3:3, v/v) with an addition of hydrochloric acid and trietylamine. The identity of the isolated alkaloids was confirmed using a high resolution HPLC-MS chromatograph. The phytochemical constituents of Coptis chinensis such as berberine, jatrorrhizine, palmatine and coptisine significantly inhibited the viability and growth of gastric cancer cell lines ACC-201 and NCI-N87 in a dose-dependent manner, with coptisine showing the highest efficacy as revealed using MTT and BrdU assays, respectively. Flow cytometry analysis confirmed the coptisine-induced population of gastric cancer cells in sub-G1 phase and apoptosis. The combination of coptisine with cisplatin at the fixed-ratio of 1:1 exerted synergistic and additive interactions in ACC-201 and NCI-N87, respectively, as determined by means of isobolographic analysis. In in vivo assay, coptisine was safe for developing zebrafish at the dose equivalent to the highest dose active in vitro, but higher doses (greater than 10 times) caused morphological abnormalities in larvae. Our findings provide a theoretical foundation to further studies on more detailed mechanisms of the bioactive compounds from Coptis chinensis Franch anti-cancer action that inhibit GC cell survival in in vitro settings.

Additive Interactions between Betulinic Acid and Two Taxanes in In Vitro Tests against Four Human Malignant Melanoma Cell Lines

The incidence of melanoma is steadily increasing worldwide. Melanoma is the most lethal skin cancer, and new therapeutic methods are being sought. Our research aimed to investigate the cytotoxic and antiproliferative effects of betulinic acid in vitro, used alone and in combination with taxanes (paclitaxel, docetaxel) in four melanoma cell lines. Isobolographic analysis allowed us to assess the interactions between these compounds. Betulinic acid had no cytotoxic effect on normal human keratinocyte HaCaT cells; the amount of LDH released by them was significantly lower compared to melanoma cell lines. The present study shows that betulinic acid significantly inhibits the growth of melanoma cell lines in vitro. The IC50 values of betulinic acid ranged from 2.21 µM to 15.94 µM against the four melanoma lines. Co-treatment of betulinic acid with paclitaxel or docetaxel generated desirable drug–drug interactions, such as an additive and additive with a tendency to synergy interactions.

Additive pharmacological interaction between sirtuin inhibitor cambinol and paclitaxel in MCF7 luminal and MDA-MB-231 triple-negative breast cancer cells

Background

Breast cancer (BC) is the most common malignancy and the leading cause of cancer-related death in women worldwide. Sirtuin inhibitors (SIRTi), belonging to the histone deacetylase inhibitors group (HDIs), are potent epigenetic drugs that have been investigated for therapeutic use in different clinical disorders, including hematological malignancies and solid tumors.

Methods

The influence of cambinol (CAM; SIRTi) used individually or in combination with standard chemotherapeutic paclitaxel (PAX) on viability (MTT assay), proliferation (BrdU assay), induction of apoptosis and cell cycle arrest (FACS analysis) was determined in MCF7 luminal and MDA-MB-231 triple-negative breast cancer (TNBC) cells. The types of pharmacological drug–drug interaction between CAM and PAX were determined by an exact and rigorous pharmacodynamic method—an isobolography, to determine the presence of synergism, addition or antagonism between analyzed drugs using a variety of fixed-dose ratios.

Results

The combination of CAM and PAX at a fixed ratio of 1:1 exerted additive interaction in the viability of MCF7 and MDA-MB-231 BC cells. Both active agents used separately reduced viability and proliferation of BC cells as well as induced apoptosis and cell cycle arrest. These effects were much more evident in MCF7 than in MDA-MB-231 BC cells. Additionally, CAM combined with PAX increased anti-cancer activity compared to PAX used alone.

Conclusion

CAM might be considered a potential therapeutic agent individually or in combined therapy with PAX against luminal or TNBC.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s43440-022-00393-w.

Anticancer Activity of Amantadine and Evaluation of Its Interactions with Selected Cytostatics in Relation to Human Melanoma Cells

Patients with Parkinson’s disease are prone to a higher incidence of melanoma. Amantadine (an anti-Parkinson drug) possesses the antiproliferative potential that can be favorable when combined with other chemotherapeutics. Cisplatin (CDDP) and mitoxantrone (MTO) are drugs used in melanoma chemotherapy, but they have many side effects. (1) Clinical observations revealed a high incidence of malignant melanoma in patients with Parkinson’s disease. Amantadine as an anti-Parkinson drug alleviates symptoms of Parkinson’s disease and theoretically, it should have anti-melanoma properties. (2) To characterize the interaction profile for combinations of amantadine with CDDP and MTO in four human melanoma cell lines (A375, SK-MEL 28, FM55P and FM55M2), type I isobolographic analysis was used in the MTT test. (3) Amantadine produces the anti-proliferative effects in various melanoma cell lines. Flow cytometry analysis indicated that amantadine induced apoptosis and G1/S phase cell cycle arrest. Western blotting analysis showed that amantadine markedly decreased cyclin-D1 protein levels and increased p21 levels. Additionally, amantadine significantly increased the Bax/Bcl-2 ratio. The combined application of amantadine with CDDP at the fixed-ratio of 1:1 exerted an additive interaction in the four studied cell lines in the MTT test. In contrast, the combination of amantadine with MTO (ratio of 1:1) produced synergistic interaction in the FM55M2 cell line in the MTT (* p < 0.05). The combination of amantadine with MTO was also additive in the remaining tested cell lines (A375, FM55P and SK-MEL28) in the MTT test. (4) Amantadine combined with MTO exerted the most desirable synergistic interaction, as assessed isobolographically. Additionally, the exposure of melanoma cell lines to amantadine in combination with CDDP or MTO augmented the induction of apoptosis mediated by amantadine alone.

Cannabidiol Interacts Antagonistically with Cisplatin and Additively with Mitoxantrone in Various Melanoma Cell Lines-An Isobolographic Analysis

The medical application of cannabidiol (CBD) has been gathering increasing attention in recent years. This non-psychotropic cannabis-derived compound possesses antiepileptic, antipsychotic, anti-inflammatory and anxiolytic properties. Recent studies report that it also exerts antineoplastic effects in multiple types of cancers, including melanoma. In this in vitro study we tried to reveal the anticancer properties of CBD in malignant melanoma cell lines (SK-MEL 28, A375, FM55P and FM55M2) administered alone, as well as in combination with mitoxantrone (MTX) or cisplatin (CDDP). The effects of CBD on the viability of melanoma cells were measured by the MTT assay; cytotoxicity was determined in the LDH test and proliferation in the BrdU test. Moreover, the safety of CBD was tested in human keratinocytes (HaCaT) in LDH and MTT tests. Results indicate that CBD reduces the viability and proliferation of melanoma-malignant cells and exerts additive interactions with MTX. Unfortunately, CBD produced antagonistic interaction when combined with CDDP. CBD does not cause significant cytotoxicity in HaCaT cell line. In conclusion, CBD may be considered as a part of melanoma multi-drug therapy when combined with MTX. A special attention should be paid to the combination of CBD with CDDP due to the antagonistic interaction observed in the studied malignant melanoma cell lines.

Antagonistic Pharmacological Interaction between Sirtuin Inhibitor Cambinol and Paclitaxel in Triple-Negative Breast Cancer Cell Lines: An Isobolographic Analysis

Breast cancer (BC) is a heterogeneous disease with different intrinsic subtypes. The most aggressive subtype of BC–triple-negative breast cancer (TNBC) is characterized by high heterogeneity and metastasis rate, poor prognosis and lack of therapeutic targets due to the absence of estrogen receptor, progesterone receptor and human epidermal growth factor receptor 2. Targeted therapies have been approved for many other cancers and even other subtypes of BC, but treatment options for TNBC are still mainly limited to chemotherapy. Therefore, new, more effective treatment regimens are needed. Combined chemotherapy with two or more active agents is considered a promising anti-neoplasm tool in order to achieve better therapeutic response and reduce therapy-related adverse effects. The study demonstrated an antagonistic effect commonly used in TNBC therapy cytostatic drug-paclitaxel (PAX) and sirtuin inhibitor: cambinol (CAM) in BT-549, MDA-MB-468 and HCC1937 TNBC cell lines. The type of pharmacological interaction was determined by a precise and rigorous pharmacodynamic method-isobolographic analysis. The cytotoxic and anti-proliferative effects of CAM used alone or combined with PAX were determined utilizing 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and 5-bromo-2′-deoxyuridine (BrdU) assays, respectively. Induction of apoptosis in TNBC cell lines after PAX and CAM treatment applied individually or in combination was determined by flow cytometry (FACS) as a number of cells with active caspase-3. It has been observed that both agents used separately inhibit cell proliferation and induce apoptosis; however, applying them in combination ameliorated antiproliferative and pro-apoptotic effects in all analyzed TNBC cell lines. Our results demonstrate that CAM and PAX used in combination act antagonistically, limiting anti-cancer efficacy and showing the importance of preclinical testing.

Ice crystal recrystallization inhibition of type I antifreeze protein, type III antifreeze protein, and antifreeze glycoprotein: effects of AF(G)Ps concentration and heat treatment

This study compared ice recrystallization behaviors of frozen dessert model systems containing type I antifreeze protein (AFP I), type III antifreeze protein (AFP III), and antifreeze glycoprotein (AFGP) at -10 °C. Specifically, effects of AF(G)P concentration and heat treatment (95 °C for 10 min) were examined. The concentration dependence of the ice recrystallization rate constant reasonably well fit a sigmoidal function: the fitting procedure was proposed, along with cooperative coefficient α, and a new index of AF(G)P ice recrystallization inhibition (IRI) activity (C50). After 95 °C heat treatment for 10 min, AFP III lost its ice crystal recrystallization inhibitory activity the most: AFP I was less affected; AFGP was almost entirely unaffected. These different thermal treatment effects might reflect a lower degree of protein aggregation because of hydrophobic interaction after heat treatment or might reflect the simplicity and flexibility of the higher order structures of AFP I and AFGP.

Assessment of Pharmacological Interactions between SIRT2 Inhibitor AGK2 and Paclitaxel in Different Molecular Subtypes of Breast Cancer Cells

Breast carcinoma (BC) is the most commonly diagnosed type of cancer in women in the world. Although the advances in the treatment of BC patients are significant, numerous side effects, severe toxicity towards normal cells as well as the multidrug resistance (MDR) phenomenon restrict the effectiveness of the therapies used. Therefore, new active compounds which decrease the MDR, extend disease-free survival, thereby ameliorating the effectiveness of the current treatment regimens, are greatly needed. Histone deacetylase inhibitors (HDIs), including sirtuin inhibitors (SIRTi), are the epigenetic antitumor agents which induce a cytotoxic effect in different types of cancer cells, including BC cells. Currently, combined forms of therapy with two or even more chemotherapeutics are promising antineoplastic tools to obtain a better response to therapy and limit adverse effects. Thus, on the one hand, much more effective chemotherapeutics, e.g., sirtuin inhibitors (SIRTi), are in demand; on the other hand, combinations of accepted cytostatics are trialed. Thus, the aim of our research was to examine the combination effects of a renowned cytotoxic drug paclitaxel (PAX) and SIRT2 inhibitor AGK2 on the proliferation and viability of the T47D, MCF7, MDA-MB-231, MDA-MB-468, BT-549 and HCC1937 BC cells. Moreover, cell cycle arrest and apoptosis induction were explored. The type of pharmacological interactions between AGK2 and PAX in different molecular subtypes of BC cells was assessed using the advanced isobolographic method. Our findings demonstrated that the tested active agents singly inhibited viability and proliferation of BC cells as well as induced cell cycle arrest and apoptosis in the cell-dependent context. Additionally, AGK2 increased the antitumor effect of PAX in most BC cell lines. We observed that, depending on the BC cell lines, the combinations of tested drugs showed synergistic, additive or antagonistic pharmacological interaction. In conclusion, our studies demonstrated that the consolidated therapy with the use of AGK2 and PAX can be considered as a potential therapeutic regimen in the personalized cure of BC patients in the future.

Palmatine, a Bioactive Protoberberine Alkaloid Isolated from Berberis cretica, Inhibits the Growth of Human Estrogen Receptor-Positive Breast Cancer Cells and Acts Synergistically and Additively with Doxorubicin

Palmatine (PLT) is a natural isoquinoline alkaloid that belongs to the class of protoberberines and exhibits a wide spectrum of pharmacological and biological properties, including anti-cancer activity. The aim of our study was to isolate PLT from the roots of Berberis cretica and investigate its cytotoxic and anti-proliferative effects in vitro alone and in combination with doxorubicine (DOX) using human ER⁺/HER2⁻ breast cancer cell lines. The alkaloid was purified by column chromatography filled with silica gel NP and Sephadex LH-20 resin developed in the mixture of methanol: water (50:50 v/v) that provided high-purity alkaloid for bioactivity studies. The purity of the alkaloid was confirmed by high resolution mass measurement and MS/MS fragmentation analysis in the HPLC-ESI-QTOF-MS/MS-based analysis. It was found that PLT treatment inhibited the viability and proliferation of breast cancer cells in a dose-dependent manner as demonstrated by MTT and BrdU assays. PLT showed a quite similar growth inhibition on breast cancer cells with IC₅₀ values ranging from 5.126 to 5.805 µg/mL. In contrast, growth of normal human breast epithelial cells was not affected by PLT. The growth inhibitory activity of PLT was related to the induction of apoptosis, as determined by Annexin V/PI staining. Moreover, PLT sensitized breast cancer cells to DOX. Isobolographic analysis revealed synergistic and additive interactions between studied agents. Our studies suggest that PLT can be a potential candidate agent for preventing and treating breast cancer.

Antagonistic Interaction between Histone Deacetylase Inhibitor: Cambinol and Cisplatin-An Isobolographic Analysis in Breast Cancer In Vitro Models

Breast cancer (BC) is the leading cause of death in women all over the world. Currently, combined chemotherapy with two or more agents is considered a promising anti-cancer tool to achieve better therapeutic response and to reduce therapy-related side effects. In our study, we demonstrated an antagonistic effect of cytostatic agent-cisplatin (CDDP) and histone deacetylase inhibitor: cambinol (CAM) for breast cancer cell lines with different phenotypes: estrogen receptor positive (MCF7, T47D) and triple negative (MDA-MB-231, MDA-MB-468). The type of pharmacological interaction was assessed by an isobolographic analysis. Our results showed that both agents used separately induced cell apoptosis; however, applying them in combination ameliorated antiproliferative effect for all BC cell lines indicating antagonistic interaction. Cell cycle analysis showed that CAM abolished cell cycle arrest in S phase, which was induced by CDDP. Additionally, CAM increased cell proliferation compared to CDDP used alone. Our data indicate that CAM and CDDP used in combination produce antagonistic interaction, which could inhibit anti-cancer treatment efficacy, showing importance of preclinical testing.

Which treatment strategy in patients with epilepsy with focal seizures uncontrolled by the first anti-seizure medication?

There is no definite proven or accepted strategy in the management of patients with focal epilepsy uncontrolled by the first anti-seizure medication (ASM). Clinical studies failed to find a significant difference in efficacy or tolerability between alternative monotherapy and/or adjunctive therapy in these patients. A second ASM is often added, the efficacy of the combination is assessed, and the dose of the first drug can be gradually reduced and withdrawn. If seizures recur, the effective combination therapy can be reinstated. In this review, we discussed experimental and clinical data about the efficacy and tolerability of the most frequently used combinations of ASMs. Animal studies suggested that the most favorable combinations are those between ASMs with different or multiple mechanisms of action, whereas combining drugs with similar pharmacodynamic properties is often associated with additive or infra-additive efficacy and additive or synergistic toxicity. Clinical studies have shown that levetiracetam (LEV) can be favorably combined with the sodium channel blockers (SCBs) lacosamide (LCM) and lamotrigine (LTG). Lamotrigine is particularly effective when associated with valproate (VPA) and possibly with LEV and topiramate (TPM). Carbamazepine (CBZ) has negative pharmacokinetic interactions with several ASMs and should not be combined with other SCBs; it could be effectively and safely combined with gabapentin (GBP) and LEV. Valproic acid has enzyme inhibiting properties and can be cautiously used with SCBs; its combination with TPM or zonisamide (ZNS) may be associated with higher toxicity.

Synergy, Additivity, and Antagonism between Cisplatin and Selected Coumarins in Human Melanoma Cells

(1) Cisplatin (CDDP) is used in melanoma chemotherapy, but it has many side effects. Hence, the search for natural substances that can reduce the dose of CDDP, and CDDP-related toxicity, is highly desired. Coumarins have many biological properties, including anticancer and antiproliferative effects. (2) An in vitro 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay on two human melanoma cell lines (FM55P and FM55M2) examined the antitumor properties of CDDP and five naturally occurring coumarins (osthole, xanthotoxin, xanthotoxol, isopimpinellin, and imperatorin). The antiproliferative effects produced by combinations of CDDP with the coumarins were assessed using type I isobolographic analysis. (3) The most potent anticancer properties of coumarins were presented by osthole and xanthotoxol. These compounds were characterized by the lowest median inhibitory concentration (IC₅₀) values relative to the FM55P and FM55M2 melanoma cells. Isobolographic analysis showed that for both melanoma cell lines, the combination of CDDP and osthole exerted synergistic and additive interactions, while the combination of CDDP and xanthotoxol exerted additive interactions. Combinations of CDDP with xanthotoxin, isopimpinellin, and imperatorin showed antagonistic and additive interactions in two melanoma cell lines. (4) The combination of CDDP and osthole was characterized by the most desirable synergistic interaction. Isobolographic analysis allows the selection of potential candidates for cancer drugs among natural substances.

Gemcitabine and Selected mTOR Inhibitors in Uterine Sarcomas and Carcinosarcoma Cells- an Isobolographic Analysis

Introduction: mTOR inhibitors are anticancer agents affecting mTOR/AKT/PI3K pathway that is one of the most important in human cancer cells. Hyperactivation of mTOR/AKT/PI3K and overexpression of this pathway members are frequently reported in uterine sarcoma and carcinosarcoma. Present study is aimed to assess the activity of the two mTOR inhibitors (rapamycin - RAP and sapanisertib - MLN) as a single agent and combined with gemcitabine (GEM, one of substances commonly used in systemic anticancer treatment) in uterine sarcoma and carcinosarcoma in vitro models. Material and methods: SK-UT-1 and SK-UT1-B (uterine carcinosarcoma), MES-SA (leiomyosarcoma) and ESS-1 (endometrial stromal sarcoma) cell lines were used. An MTT assay was performed to examine the cytotoxicity of RAP, MLN and mixtures: RAP+MLN, RAP+GEM, MLN+GEM against these cells. The interactions between tested compounds were assessed in isobolographic analysis. Results and conclusions: Carcinosarcoma cell lines (both SK-UT-1 and SK-UT-1B) do not respond to RAP and respond relatively weakly to MLN treatment. Additive and supraadditive effects were noted for combined treatment with GEM and MLN. Endometrial stromal sarcoma cell line (ESS-1) occured to be sensitive to both RAP and MLN, but the response was stronger for MLN. Additive effect of all tested drug combinations was observed for ESS-1. Leiomyosarcoma cell line (MES-SA) was found sensitive to both mTOR inhibitors. Additive effects in combinations of GEM, RAP and MLN were observed, what makes them promising for future preclinical and clinical trials. Additivity with slight tendency towards antagonism between GEM and MLN observed in MES-SA cell line is unexpected finding and might prompt the mechanistic research aimed to explain this phenomenon.

Polygonogram with isobolographic synergy for three-drug combinations of phenobarbital with second-generation antiepileptic drugs in the tonic-clonic seizure model in mice

Background

Combination therapy consisting of two or more antiepileptic drugs (AEDs) is usually prescribed for patients with refractory epilepsy. The drug–drug interactions, which may occur among currently available AEDs, are the principal criterion taken by physicians when prescribing the AED combination to the patients. Unfortunately, the number of possible three-drug combinations tremendously increases along with the clinical approval of novel AEDs.

Aim

To isobolographically characterize three-drug interactions of phenobarbital (PB) with lamotrigine (LTG), oxcarbazepine (OXC), pregabalin (PGB) and topiramate (TPM), the maximal electroshock-induced (MES) seizure model was used in male albino Swiss mice.

Materials and method

The MES-induced seizures in mice were generated by alternating current delivered via auricular electrodes. To classify interactions for 6 various three-drug combinations of AEDs (i.e., PB + TPM + PGB, PB + OXC + TPM, PB + LTG + TPM, PB + OXC + PGB, PB + LTG + PGB and PB + LTG + OXC), the type I isobolographic analysis was used. Total brain concentrations of PB were measured by fluorescent polarization immunoassay technique.

Results

The three-drug mixtures of PB + TPM + PGB, PB + OXC + TPM, PB + LTG + TPM, PB + OXC + PGB, PB + LTG + PGB and PB + LTG + OXC protected the male albino Swiss mice from MES-induced seizures. All the observed interactions in this seizure model were supra-additive (synergistic) (p < 0.001), except for the combination of PB + LTG + OXC, which was additive. It was unable to show the impact of the studied second-generation AEDs on total brain content of PB in mice.

Conclusions

The synergistic interactions among PB and LTG, OXC, PGB and TPM in the mouse MES model are worthy of being transferred to clinical trials, especially for the patients with drug resistant epilepsy, who would benefit these treatment options.

Sub-additive (antagonistic) interaction of lacosamide with lamotrigine and valproate in the maximal electroshock-induced seizure model in mice: an isobolographic analysis

BACKGROUND

Launching polytherapy with two or three antiseizure drugs (ASDs) in patients with epilepsy is still problematic. The choice of ASDs to combine them together is usually based on clinicians' experience and it requires knowledge about mechanisms of action of the studied ASDs and their drug-drug interactions, whose nature may be favorable, neutral or unfavorable. To characterize three-drug interaction among lacosamide (LCM), lamotrigine (LTG) and valproate (VPA), the type I isobolographic analysis was used. The antiseizure effects of three-drug combination were analyzed in a model of maximal electroshock-induced seizures (MES) in albino Swiss mice.

MATERIALS AND METHODS

The seizure activity in mice was evoked by alternating current stimulation (25 mA, 500 V, 50 Hz, 0.2 s). Both, the type I isobolographic analysis and the test of parallelism of dose-response effects of the ASDs were used so as to properly classify interaction among three ASDs, administered in a fixed ratio combination of 1:1:1.

RESULTS

The three-drug mixture of LCM, LTG and VPA at the fixed ratio of 1:1:1 protected the experimental mice from MES-induced seizures; however, the reported interaction was sub-additive (antagonistic; p < 0.01) with isobolography.

CONCLUSION

The antagonistic pharmacodynamic interaction among LCM, LTG and VPA in the MES test in mice cannot be transferred to clinical settings and this unfavorable combination should not be recommended for patients with epilepsy.

Polygonogram and isobolographic analysis of interactions between various novel antiepileptic drugs in the 6-Hz corneal stimulation-induced seizure model in mice

Pharmacotherapy with two antiepileptic drugs in combination is usually prescribed to epilepsy patients with refractory seizures. The choice of antiepileptic drugs in combination should be based on synergistic cooperation of the drugs with respect to suppression of seizures. The selection of synergistic interactions between antiepileptic drugs is challenging issue for physicians, especially, if 25 antiepileptic drugs are currently available and approved to treat epilepsy patients. The aim of this study was to determine all possible interactions among 5 second-generation antiepileptic drugs (gabapentin (GBP), lacosamide (LCM), levetiracetam (LEV), pregabalin (PGB) and retigabine (RTG)) in the 6-Hz corneal stimulation-induced seizure model in adult male albino Swiss mice. The anticonvulsant effects of 10 various two-drug combinations of antiepileptic drugs were evaluated with type I isobolographic analysis associated with graphical presentation of polygonogram to visualize the types of interactions. Isobolographic analysis revealed that 7 two-drug combinations of LEV+RTG, LEV+LCM, GBP+RTG, PGB+LEV, GBP+LEV, PGB+RTG, PGB+LCM were synergistic in the 6-Hz corneal stimulation-induced seizure model in mice. The additive interaction was observed for the combinations of GBP+LCM, GBP+PGB, and RTG+LCM in this seizure model in mice. The most beneficial combination, offering the highest level of synergistic suppression of seizures in mice was that of LEV+RTG, whereas the most additive combination that protected the animals from seizures was that reporting additivity for RTG+LCM. The strength of interaction for two-drug combinations can be arranged from the synergistic to the additive, as follows: LEV+RTG > LEV+LCM > GBP+RTG > PGB+LEV > GBP+LEV > PGB+RTG > PGB+LCM > GBP+LCM > GBP+PGB > RTG+LCM.

Synergistic or Additive Pharmacological Interactions between Magnoflorine and Cisplatin in Human Cancer Cells of Different Histological Origin

Magnoflorine is an aporphine alkaloid present in plant species belonging to the Berberidaceae, Magnoliaceae, Menispermaceae, or Papaveraceae botanical families. The interest of magnoflorine has increased recently due to its multiplicity of pharmacological properties. The aim of this study was the analysis of combined anti-proliferative effect of magnoflorine and cisplatin and the assessment of drug–drug pharmacological interaction between these agents using isobolographic method in MDA-MB-468 human breast, NCIH1299 lung, TE671 rhabdomyosarcoma, or T98G glioblastoma cancer cell lines. Magnoflorine in combination with cisplatin at a fixed ratio of 1:1 augmented their anticancer action and yielded synergistic or additive pharmacological interactions by means of isobolographic method, therefore combined therapy using these two active agents can be a promising chemotherapy regimen in the treatment of some types of breast, lung, rhabdomyosarcoma, and glioblastoma cancers.

Pharmacodynamic interactions of antiepileptic drugs: From bench to clinical practice

BACKGROUND

Approximately 50% of patients do not achieve seizure control with antiepileptic drug (AED) monotherapy, and polytherapy, with more than one AED, is often required. To date, no evidence-based criteria on how to combine AEDs exist.

OBJECTIVE

This narrative review aimed to provide critical findings of the available literature about the role of pharmacodynamic AEDs' interactions in patients whose epilepsies were treated with polytherapy.

METHODS

Electronic databases, Medical Literature Analysis and Retrieval System Online (MEDLINE) and Excerpta Medica dataBASE (EMBASE), were systematically searched to identify relevant studies on pharmacodynamic AEDs' interactions in patients with epilepsy.

RESULTS AND CONCLUSION

Most data on AED combinations are coming from animal models and preclinical studies. Combining AEDs with different mechanisms of actions seems to have greater effectiveness and lower risk of adverse event development. Conversely, the combination of AEDs may cause pharmacodynamic synergistic effects that may result in not only increased efficacy but also more adverse effects. Despite some AED associations that have been proven to be effective in specific epilepsy/seizure type (e.g., phenobarbital+/phenytoin for tonic seizures and ethosiximide + valproate for absences; lamotrigine + valproate for various epilepsy/seizure types), no clear and definitive evidence exists about AED combinations in humans. Examples of pharmacodynamic interactions that possibly explain the synergistic effects on efficacy or adverse effects include the combination between vigabatrin or pregabalin and sodium channel blockers (supra-additive antiseizure effect) and lacosamide combined with other sodium channel blockers (infra-additive antiseizure effect and neurotoxicity synergistic). The pharmacodynamic lamotrigine-valproate interaction is also supported by synergistic adverse events. Therefore, well-designed double-blind prospective studies recruiting a sufficient number of patients possibly with a crossover design and carefully ascertain the role of pharmacokinetic interactions and variations of AEDs' levels in the blood are needed.

N-Benzyl-(2,5-dioxopyrrolidin-1-yl)propanamide (AS-1) with Hybrid Structure as a Candidate for a Broad-Spectrum Antiepileptic Drug

In our recent studies, we identified compound N-benzyl-2-(2,5-dioxopyrrolidin-1-yl)propanamide (AS-1) as a broad-spectrum hybrid anticonvulsant which showed potent protection across the most important animal acute seizure models such as the maximal electroshock (MES) test, the subcutaneous pentylenetetrazole (s.c. PTZ) test, and the 6-Hz (32 mA) test in mice. Therefore, AS-1 may be recognized as a candidate for new anticonvulsant effective in different types of human epilepsy with a favorable safety margin profile determined in the rotarod test in mice. In the aim of further pharmacological evaluation of AS-1, in the current study, we examined its activity in the 6-Hz (44 mA) test, which is known as the model of drug-resistant epilepsy. Furthermore, we determined also the antiseizure activity in the kindling model of epilepsy induced by repeated injection of pentylenetetrazole (PTZ) in mice. As a result, AS-1 revealed relatively potent protection in the 6-Hz (44 mA) test, as well as delayed the progression of kindling induced by repeated injection of PTZ in mice at doses of 15 mg/kg, 30 mg/kg, and 60 mg/kg. Importantly, the isobolographic analysis showed that a combination of AS-1 and valproic acid (VPA) at the fixed ratio of 1:1 displayed a supra-additive (synergistic) interaction against PTZ-induced seizures in mice. Thus, AS-1 may be potentially used in an add-on therapy with VPA. Moreover, incubation of zebrafish larvae with AS-1 substantially decreased the number, cumulative but not the mean duration of epileptiform-like events in electroencephalographic assay. Finally, the in vitro ADME-Tox studies revealed that AS-1 is characterized by a very good permeability in the parallel artificial membrane permeability assay test, excellent metabolic stability on human liver microsomes (HLMs), no significant influence on CYP3A4/CYP2D6 activity, and moderate inhibition of CYP2C9 in a concentration of 10 μM, as well as no hepatotoxic properties in HepG2 cells (concentration of 10 μM).

Isobolographic Analysis Demonstrates the Additive and Synergistic Effects of Gemcitabine Combined with Fucoidan in Uterine Sarcomas and Carcinosarcoma Cells

Background: Uterine sarcomas and carcinosarcoma are associated with unfavorable prognosis. The regimens that are used in chemotherapy are associated with high incidence of side effects and usually do not significantly increase patients’ survival rates. In this study we investigated the activity and interactions between gemcitabine and fucoidan, the natural compound known for its anti-tumor properties, in human sarcomas and carcinosarcoma cell models. Methods: SK-UT-1, SK-UT1-B (carcinosarcoma), MES-SA (leiomyosarcoma), and ESS-1 (endometrial stromal sarcoma) cell lines were used for the experiments. Cells were incubated in the presence of gemcitabine, fucoidan, and mixtures, after the incubation the MTT tests were performed. In order to assess the interactions between tested compounds isobolographic analysis was performed. Additional assessments of apoptosis and cell cycle were done. Results: Additive effect of combined treatment with gemcitabine and fucoidan was observed in ESS-1 and SK-UT-1 cell line. Although the supra-additive (synergistic) effect noticed in SK-UT-1B cell line. It was not possible to determine the interactions of fucoidan and gemcitabine in MES-SA cell line due to insufficient response to treatment. Addition of fucoidan to gemcitabine enhances its proapoptotic activity, what was observed especially in ESS-1 and SK-UT-1B cell lines. The arrest of cell cycle induced by mixture of gemcitabine and fucoidan, superior comparing gemcitabine alone was observed in SK-UT-1B. Conclusions: Obtained data showed that a combination of fucoidan and gemcitabine in uterine endometrial stromal sarcoma and carcinosarcoma cell lines has additive or even synergistic effect in decreasing cell viability. Furthermore, this drug combination induces apoptosis and arrest of cell cycle. The resistance of uterine leiomyosarcoma cell line, justifies searching for other drugs combinations to improve therapy efficacy.

Anticonvulsant and neurotoxic effects of a novel 1,2,4-triazole-3-thione derivative (TPF-34) and its isobolographic interaction profile with classical antiepileptic drugs in mice

BACKGROUND

Anticonvulsant and acute toxic effects of 5-[(3-fluorophenyl)ethyl]-4-(n-hexyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione (TPF-34)-a candidate for novel antiepileptic drug-were examined in the maximal electroshock-induced seizure (MES) model and rotarod test in mice. The interaction profile of TPF-34 with four classical antiepileptic drugs (carbamazepine, phenobarbital, phenytoin and valproate) was also studied in the mouse MES model.

METHODS

Both ED₅₀ and TD₅₀ values for TPF-34 were determined at four treatment times (15, 30, 60 and 120 min after i.p. administration) in the MES model and rotarod test in adult male albino Swiss mice, respectively. The influence of TPF-34 on the protective anticonvulsant action of carbamazepine, phenobarbital, phenytoin and valproate in the mouse MES model was assessed with isobolographic analysis of interaction. Total brain antiepileptic drug concentrations were measured with fluorescence polarization immunoassay.

RESULTS

TPF-34, when administered alone at four pretreatment times (15, 30, 60 and 120 min before experiments), possessed a favorable preclinical profile with the protective index (a ratio of TD₅₀ and ED₅₀ values) ranging from 2.89 to 3.53. Moreover, TPF-34, when combined with carbamazepine, phenobarbital, phenytoin and valproate, exerted an additive interaction in the MES model in mice. TPF-34 had no impact on total brain antiepileptic drug concentrations in mice.

CONCLUSIONS

A protective index value higher than 3 allows recommending TPF-34 as a promising antiepileptic drug candidate for further preclinical testing using other experimental seizure models. The additive interaction of TPF-34 with carbamazepine, phenobarbital, phenytoin and valproate in the mouse MES model is worthy of recommendation to further clinical studies.

A viewpoint on rational and irrational fixed-drug combinations

INTRODUCTION

Considering that there are around 30% of patients with epilepsy resistant to monotherapy, the use of synergistic combinations of antiepileptic drugs is of particular importance. This review shows most beneficial as well as irrational combined treatments both from an experimental and clinical point of view. Areas covered: Preferably, experimental data derived from studies evaluating synergy, additivity, or antagonism by relevant methods, in terms of anticonvulsant or neurotoxic effects and pharmacokinetic data have been considered. Although there have been no randomized clinical trials on this issue, the clinical data have been analyzed from studies on considerable numbers of patients. Case-report studies have been not considered. Expert commentary: The experimental data provide a strong support that co-administration of lamotrigine with carbamazepine is negative, considering the anticonvulsant and neurotoxic effects. Clinical reports do not entirely support this conclusion. Other experimentally documented negative combinations comprise lamotrigine+ oxcarbazepine and oxcarbazepine+ phenytoin. From the experimental and clinical point of view, a combination of lamotrigine+ valproate may deserve recommendation. Other most positive experimental and clinical combinations include carbamazepine+valproate, phenytoin+phenobarbital, carbamazepine+gabapentin, carbamazepine+topiramate, levetiracetam+valproate, levetiracetam+carbamazepine. Certainly, experimental data have some limitations (non-epileptic animals, acute administration of antiepileptic drugs) so all experimental recommendations need a careful clinical evaluation.

Superior anticancer activity is demonstrated by total extract of Curcuma longa L. as opposed to individual curcuminoids separated by centrifugal partition chromatography

Three curcuminoids: bisdemethoxycurcumin, demethoxycurcumin, and curcumin from turmeric were successfully separated by a high capacity solvent system composed of heptane: chloroform: methanol: water mixture (5: 6: 3: 2 v/v/v/v) tailored for centrifugal partition chromatographs at K-values of 0.504, 1.057, 1.644, respectively. These three ferulic acid derivatives obtained at a purity rate exceeding 95% were analysed by an HPLC-MS spectrometer. Turmeric extract inhibited the proliferation/viability of A549 human lung cancer, HT29 colon cancer, and T98G glioblastoma cell lines in (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) tetrazolium reduction assay (MTT). Single curcuminoids significantly decreased the viability/proliferation of lung cancer cells in a dose-dependent manner. However, total extract displayed the superior anticancer activity in the investigated cell lines. Crude extract in combination with cisplatin augmented the decrease in the viability of cancer cells compared with single compound treatment in A549 lung cancer cells. Total extract of Curcuma longa could be regarded as being more effective against lung cancer cells in vitro than its separated compounds.

Beneficial Combination of Lacosamide with Retigabine in Experimental Animals: An Isobolographic Analysis

BACKGROUND/AIM

To isobolographically determine the types of interactions that occur between retigabine and lacosamide (LCM; two third-generation antiepileptic drugs) with respect to their anticonvulsant activity and acute adverse effects (sedation) in the maximal electroshock-induced seizures (MES) and chimney test (motor performance) in adult male Swiss mice.

METHODS

Type I isobolographic analysis for nonparallel dose-response effects for the combination of retigabine with LCM (at the fixed-ratio of 1:1) in both the MES and chimney test in mice was performed. Brain concentrations of retigabine and LCM were measured by high-pressure liquid chromatography (HPLC) to characterize any pharmacokinetic interactions occurring when combining these drugs.

RESULTS

Linear regression analysis revealed that retigabine had its dose-response effect line nonparallel to that of LCM in both the MES and chimney tests. The type I isobolographic analysis illustrated that retigabine combined with LCM (fixed-ratio of 1:1) exerted an additive interaction in the mouse MES model and sub-additivity (antagonism) in the chimney test. With HPLC, retigabine and LCM did not mutually change their total brain concentrations, thereby confirming the pharmacodynamic nature of the interaction.

CONCLUSION

LCM combined with retigabine possesses a beneficial preclinical profile (benefit index ranged from 2.07 to 2.50) and this 2-drug combination is worth recommending as treatment plan to patients with pharmacoresistant epilepsy.

Review about gabapentin misuse, interactions, contraindications and side effects

The current work is targeted to review the risks of gabapentin misuse, its potential interactions with other drugs, side effects and use contraindications. This review consists of a total of 99 biographical references (from the year 1983 to 2016). A publication search of PubMed was performed from January 1983 to December 2016. It included animal studies, clinical studies, case studies and reviews related to gabapentin misuse, potential interactions, side effects and use contraindications. The search terms were gabapentin, anticonvulsant and antiepileptic. In general, it seems that gabapentin has risks of being misused based on the increased level of prescriptions, related fatalities, recreational misuse and higher doses of self-administration. The main reasons for gabapentin misuse are as follows: getting high, alleviating opioid withdrawal symptoms and potentiating methadone effects. Some of the main substances that interact with gabapentin are morphine, caffeine, losartan, ethacrynic acid, phenytoin, mefloquine and magnesium oxide. Some of the side effects caused by gabapentin are teratogenicity, hypoventilation, respiratory failure and myopathy. Finally, reports in general contraindicate the use of gabapentin in conditions such as myasthenia gravis and myoclonus.

Histone Deacetylase Inhibitor SAHA as Potential Targeted Therapy Agent for Larynx Cancer Cells

Objective: Laryngeal squamous cell carcinoma is one of the most common malignant tumors in the head and neck region. Due to the poor response to chemotherapeutics in patients and low survival rate, successful treatment of larynx cancer still remains a challenge. Therefore, the identification of novel treatment options is needed. We investigated the anticancer effects of suberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor, on two different laryngeal cancer cell lines RK33 and RK45. We also studied the antiproliferative action of SAHA in combination with cisplatin and defined the type of pharmacological interaction between these drugs. Materials and Methods: Viability and proliferation of larynx cancer cell lines were studied by methylthiazolyldiphenyl-tetrazolium bromide method and 5-bromo-2-deoxyuridine incorporation assay, respectively. The type of interaction between SAHA and cisplatin was determined by an isobolographic analysis. Western blotting, flow cytometry and quantitative polymerase chain reaction method were used to determine acetylation of histone H3, cell cycle progression and genes expression, respectively. Apoptosis was assessed by means of nucleosomes released to cytosol. Results: SAHA alone or in combination with cisplatin inhibited larynx cancer cells proliferation, whereas displayed relatively low toxicity against normal cells - primary cultures of human skin fibroblasts. The mixture of SAHA with cisplatin exerted additive and synergistic interaction in RK33 and RK45 cells, respectively. We showed that SAHA induced hyperacetylation of histone H3 K9, K14 and K23 and triggered apoptosis. SAHA also caused cell cycle arrest by upregulation of CDKN1A and downregulation of CCND1 encoding p21WAF1/CIP1 and cyclin D1 proteins, respectively. Conclusion: Our studies demonstrated that SAHA may be considered as a potential therapeutic agent against larynx tumors.

Assessment of Interactions between Cisplatin and Two Histone Deacetylase Inhibitors in MCF7, T47D and MDA-MB-231 Human Breast Cancer Cell Lines - An Isobolographic Analysis

Histone deacetylase inhibitors (HDIs) are promising anticancer drugs, which inhibit proliferation of a wide variety of cancer cells including breast carcinoma cells. In the present study, we investigated the influence of valproic acid (VPA) and suberoylanilide hydroxamic acid (SAHA, vorinostat), alone or in combination with cisplatin (CDDP) on proliferation, induction of apoptosis and cell cycle progression in MCF7, T47D and MDA-MB-231 human breast carcinoma cell lines. The type of interaction between HDIs and CDDP was determined by an isobolographic analysis. The isobolographic analysis is a very precise and rigorous pharmacodynamic method, to determine the presence of synergism, addition or antagonism between different drugs with using variety of fixed dose ratios. Our experiments show that the combinations of CDDP with SAHA or VPA at a fixed-ratio of 1:1 exerted additive interaction in the viability of MCF7 cells, while in T47D cells there was a tendency to synergy. In contrast, sub-additive (antagonistic) interaction was observed for the combination of CDDP with VPA in MDA-MB-231 “triple-negative” (i.e. estrogen receptor negative, progesterone receptor negative, and HER-2 negative) human breast cancer cells, whereas combination of CDDP with SAHA in the same MDA-MB-231 cell line yielded additive interaction. Additionally, combined HDIs/CDDP treatment resulted in increase in apoptosis and cell cycle arrest in all tested breast cancer cell lines in comparison with a single therapy. In conclusion, the additive interaction of CDDP with SAHA or VPA suggests that HDIs could be combined with CDDP in order to optimize treatment regimen in some human breast cancers.

Effects of WIN 55,212-2 (a synthetic cannabinoid CB1 and CB2 receptor agonist) on the anticonvulsant activity of various novel antiepileptic drugs against 6 Hz-induced psychomotor seizures in mice

The purpose of this study was to determine the influence of WIN 55,212-2 mesylate (WIN-a non-selective cannabinoid CB1 and CB2 receptor agonist) on the anticonvulsant activity of various second- and third-generation antiepileptic drugs (i.e., gabapentin, lacosamide, levetiracetam, oxcarbazepine, pregabalin and tiagabine) in the mouse 6 Hz-induced psychomotor seizure model. Psychomotor seizures were evoked in albino Swiss mice by a current (32 mA, 6 Hz, 3s stimulus duration) delivered via ocular electrodes. Additionally, total brain antiepileptic drug concentrations were measured. Results indicate that WIN (5 mg/kg, administered i.p.) significantly potentiated the anticonvulsant action of gabapentin (P < 0.05) and levetiracetam (P < 0.01), but not that of lacosamide, oxcarbazepine, pregabalin or tiagabine in the mouse psychomotor seizure model. Moreover, WIN (2.5 mg/kg) had no significant effect on the anticonvulsant activity of all tested antiepileptic drugs in the 6 Hz test in mice. Measurement of total brain antiepileptic drug concentrations revealed that WIN (5 mg/kg) had no impact on gabapentin or levetiracetam total brain concentrations, indicating the pharmacodynamic nature of interaction between these antiepileptic drugs in the mouse 6Hz model. In conclusion, WIN in combination with gabapentin and levetiracetam exerts beneficial anticonvulsant pharmacodynamic interactions in the mouse psychomotor seizure model.

Isobolographic analysis of the mechanisms of action of anticonvulsants from a combination effect

The nature of the pharmacodynamic interactions of drugs is influenced by the drugs׳ mechanisms of action. It has been hypothesized that drugs with different mechanisms are likely to interact synergistically, whereas those with similar mechanisms seem to produce additive interactions. In this review, we describe an extensive investigation of the published literature on drug combinations of anticonvulsants, the nature of the interaction of which has been evaluated by type I and II isobolographic analyses and the subthreshold method. The molecular targets of antiepileptic drugs (AEDs) include Na(+) and Ca(2+) channels, GABA type-A receptor, and glutamate receptors such as NMDA and AMPA/kainate receptors. The results of this review indicate that the nature of interactions evaluated by type I isobolographic analyses but not by the two other methods seems to be consistent with the above hypothesis. Type I isobolographic analyses may be used not only for evaluating drug combinations but also for predicting the targets of new drugs.

Understanding synergy

Analysis of the interactive effects of combinations of hormones or other manipulations with qualitatively similar individual effects is an important topic in basic and clinical endocrinology as well as other branches of basic and clinical research related to integrative physiology. Functional, as opposed to mechanistic, analyses of interactions rely on the concept of synergy, which can be defined qualitatively as a cooperative action or quantitatively as a supra-additive effect according to some metric for the addition of different dose-effect curves. Unfortunately, dose-effect curve addition is far from straightforward; rather, it requires the development of an axiomatic mathematical theory. I review the mathematical soundness, face validity, and utility of the most frequently used approaches to supra-additive synergy. These criteria highlight serious problems in the two most common synergy approaches, response additivity and Loewe additivity, which is the basis of the isobole and related response surface approaches. I conclude that there is no adequate, generally applicable, supra-additive synergy metric appropriate for endocrinology or any other field of basic and clinical integrative physiology. I recommend that these metrics be abandoned in favor of the simpler definition of synergy as a cooperative, i.e., nonantagonistic, effect. This simple definition avoids mathematical difficulties, is easily applicable, meets regulatory requirements for combination therapy development, and suffices to advance phenomenological basic research to mechanistic studies of interactions and clinical combination therapy research.

Synergistic interaction of pregabalin with the synthetic cannabinoid WIN 55,212-2 mesylate in the hot-plate test in mice: an isobolographic analysis

BACKGROUND

The aim of the study was to determine the type of interaction between pregabalin (a 3(rd)-generation antiepileptic drug) and WIN 55,212-2 mesylate (WIN - a highly potent non-selective cannabinoid CB1 and CB2 receptor agonist) administered in combination at a fixed ratio of 1:1, in the acute thermal pain model (hot-plate test) in mice.

METHODS

Linear regression analysis was used to evaluate the dose-response relationships between logarithms of drug doses and their resultant maximum possible antinociceptive effects in the mouse hot-plate test. From linear equations, doses were calculated that increased the antinociceptive effect by 30% (ED(30) values) for pregabalin, WIN, and their combination. The type of interaction between pregabalin and WIN was assessed using the isobolographic analysis.

RESULTS

Results indicated that both compounds produced a definite antinociceptive effect, and the experimentally-derived ED(30) values for pregabalin and WIN, when applied alone, were 29.4 mg/kg and 10.5 mg/kg, respectively. With isobolography, the experimentally derived ED(30 mix) value for the fixed ratio combination of 1:1 was 5.7 mg/kg, and differed significantly from the theoretically calculated ED(30 add) value of 19.95 mg/kg (p < 0.01), indicating synergistic interaction between pregabalin and WIN in the hot-plate test in mice.

CONCLUSIONS

Isobolographic analysis demonstrated that the combination of WIN with pregabalin at a fixed ratio of 1:1 exerted synergistic interaction in the mouse model of acute thermal pain. If the results from this study could be adapted to clinical settings, the combination of WIN with pregabalin might be beneficial for pain relief in humans.

Anticonvulsant action of indazole

Here we report that indazole is characterized as a potential anticonvulsant, inhibiting pentylenetetrazole-, electroshock- and strychnine-induced convulsions in mice (ED50's: 39.9, 43.2 and 82.4 mg/kg, respectively) but not bicuculline- and picrotoxin-induced convulsions. The median toxic dose (TD(50)) of indazole was 52.3 mg/kg by the minimal motor impairment test. Therefore, nontoxic doses produced anticonvulsant activity against pentylenetetrazole- and electroshock-induced seizures. Indazole (50 mg/kg) had no effect on spontaneous activity but induced hypothermia. It also inhibited the metabolism of dopamine and 5-hydroxytryptamine in the brain in vivo and the activities of monoamine oxidase A and B in vitro, with IC(50) values of 20.6 μM and 16.3 μM, respectively. However, these inhibitory effects do not account for the anticonvulsant activity because treatment with typical monoamine oxidase inhibitors such as pargyline or tranylcypromine did not completely reproduce the anticonvulsant activity of indazole. In the animal seizure models tested, the anticonvulsant profile of indazole most resembled that of gabapentin and somewhat resembled those of the AMPA/kainate antagonist NBQX and the sodium channel inhibitor phenytoin, but differed from that of benzodiazepine. The isobolographic analyses showed that the interactive mode of indazole with gabapentin, NBQX or phenytoin is additive. These results suggest that indazole has anticonvulsant activity and multiple mechanisms.

Additive interactions of pregabalin with lamotrigine, oxcarbazepine and topiramate in the mouse maximal electroshock-induced seizure model: a type I isobolographic analysis for non-parallel dose-response relationship curves

The aim of this study was to characterize the anticonvulsant effects of pregabalin (PGB-a third-generation antiepileptic drug) in combination with three second-generation antiepileptic drugs (i.e., lamotrigine [LTG], oxcarbazepine [OXC] and topiramate [TPM]) in the mouse maximal electroshock (MES)-induced seizure model by using the type I isobolographic analysis for non-parallel dose-response relationship curves (DRRCs). Tonic hind limb extension (seizure activity) was evoked in adult male albino Swiss mice by a current (sine-wave, 25mA, 500V, 50Hz, 0.2s stimulus duration) delivered via auricular electrodes. Potential adverse-effect profiles of interactions of PGB with LTG, OXC and TPM at the fixed-ratio of 1:1 in the MES test with respect to motor performance, long-term memory and skeletal muscular strength were measured. In the mouse MES model, PGB administered singly had its DRRC non-parallel to that for LTG, OXC and TPM. With type I isobolography for non-parallel DRRCs, the combinations of PGB with LTG, OXC and TPM at the fixed-ratio of 1:1 exerted additive interaction. In all combinations, neither motor coordination, long-term memory nor muscular strength were affected. In conclusion, the additive interactions between PGB and LTG, OXC and TPM are worthy of consideration while extrapolating the results from this study to clinical settings.

Interactions of stiripentol with clobazam and valproate in the mouse maximal electroshock-induced seizure model

The aim of this study was to characterize the anticonvulsant effects of stiripentol (STP) in combination with clobazam [CLB], and valproate [VPA]) in the mouse maximal electroshock (MES)-induced seizure model using the type I isobolographic analysis for parallel and non-parallel dose-response relationship curves (DRRCs). Potential adverse-effect profiles of interactions of STP with CLB and VPA at the fixed-ratio of 1:1 in the MES test with respect to motor performance, long-term memory and skeletal muscular strength were measured along with total brain antiepileptic drug concentrations. In the mouse MES model, STP administered singly had its DRRC non-parallel to that for CLB and, simultaneously, parallel to that for VPA. With type I isobolography for parallel DRRCs, the combinations of STP with VPA at three fixed-ratios of 1:3, 1:1 and 3:1 exerted sub-additive (antagonistic) interaction. Isobolography for non-parallel DRRCs revealed that the combination of STP with CLB at the fixed-ratio of 1:1 produced additive interaction. For all combinations, neither motor coordination, long-term memory nor muscular strength was affected. Total brain antiepileptic drug concentrations revealed bi-direction changes with the most profound being an 18.6-fold increase in CLB by STP and a 2.3-fold increase in STP by VPA. In conclusion, the additive interaction between STP and CLB was associated with a concurrent pharmacokinetic interaction and these data may explain the clinical efficacy seen with this combination. In contrast, the antagonism between STP and VPA was surprising since synergism is observed clinically.

Pharmacodynamic interactions between antiepileptic drugs: preclinical data based on isobolography

BACKGROUND

At least 20 - 30% of epileptic patients do not sufficiently respond to monotherapy. Some of them can benefit from drug combinations; hence, animal data may provide some useful novel clues for rational polytherapy.

OBJECTIVE

To review combinations of antiepileptic drugs, evaluated with the help of isobolographic analysis, in terms of their efficacy and adverse effects.

METHODS

A literature search, on the basis of experimental studies, with no time limit was carried out.

RESULTS/CONCLUSION

Preclinical data indicate that a synergy occurred for the combinations of valproate + phenytoin, valproate + ethosuximide, lamotrigine + valproate, gabapentin + valproate, gabapentin + carbamazepine, topiramate + carbamazepine, topiramate + valproate, topiramate + oxcarbazepine, levetiracetam + topiramate, levetiracetam + oxcarbazepine, oxcarbazepine + gabapentin, tiagabine + gabapentin and lamotrigine + topiramate. On the other hand, lamotrigine combined with carbamazepine or oxcarbazepine resulted in a clear-cut antagonism. Interestingly, a combination of oxcarbazepine + clonazepam produced variable responses, including synergy, additivity or antagonism, depending on the dose ratio of these drugs. In no case did pharmacokinetic factors contribute to the final analysis of the effects of drug combinations. Pharmacokinetic factors can contribute to the final effect of drug combinations,such as when stiripentol is added to valproate, or clobazam is added to valproate. It may be concluded that the rational treatment of drug-resistant epilepsy needs to consider the results of preclinical studies.

Interactions of 1-methyl-1,2,3,4-tetrahydroisoquinoline with lamotrigine, oxcarbazepine, pregabalin, and topiramate in the mouse maximal electroshock-induced seizure model: a type I isobolographic analysis

The aim of this study was to characterize the anticonvulsant effects of 1-methyl-1,2,3,4-tetrahydroisoquinoline (MeTHIQ--an endogenous parkinsonism-preventing substance) in combination with four second-generation antiepileptic drugs (AEDs: lamotrigine [LTG], oxcarbazepine [OXC], pregabalin [PGB], and topiramate [TPM]) in the mouse maximal electroshock (MES)-induced seizure model by using the type I isobolographic analysis for parallel and non-parallel dose-response relationship curves (DRRCs). Potential adverse-effect profiles of interactions of MeTHIQ with LTG, OXC, PGB and TPM at the fixed-ratio of 1:1 from the MES test with respect to motor performance, long-term memory and skeletal muscular strength were measured along with total brain concentrations of MeTHIQ and TPM. In the mouse MES model, MeTHIQ administered singly had its DRRC parallel to those for OXC and TPM, and simultaneously, non-parallel to those for LTG and PGB. With type I isobolography for parallel DRRCs, the combination of MeTHIQ with TPM at three fixed-ratios of 1:3, 1:1 and 3:1 exerted supra-additive (synergistic) interaction, whereas the combination of MeTHIQ with OXC at the fixed-ratios of 1:3, 1:1 and 3:1 produced additive interaction. Similarly, the type I isobolography for non-parallel DRRCs revealed that the combination of MeTHIQ with LTG and PGB at the fixed-ratio of 1:1 produced additive interaction. For all combinations, neither motor coordination, long-term memory nor muscular strength were affected. Total brain concentrations of MeTHIQ and TPM revealed no significant changes in their concentrations when the drugs were combined at the fixed-ratios of 1:3, 1:1 and 3:1. In conclusion, the synergistic interaction of MeTHIQ with TPM at the fixed-ratios of 1:3, 1:1 and 3:1 against MES-induced seizures was pharmacodynamic in nature and thus, it is worthy of consideration in further clinical settings. The combinations of MeTHIQ with LTG, OXC and PGB were neutral in the mouse MES model.

Interaction of tiagabine with valproate in the mouse pentylenetetrazole-induced seizure model: an isobolographic analysis for non-parallel dose-response relationship curves

PURPOSE

To characterize the interaction between tiagabine (TGB) and valproate (VPA)--two antiepileptic drugs in the mouse pentylenetetrazole (PTZ)-induced clonic seizure model, type I isobolographic analysis for non-parallel dose-response relationship curves (DRRCs) was used.

MATERIAL AND METHODS

Clonic seizures were evoked in albino Swiss mice by subcutaneous injection of PTZ at its CD97 (100 mg/ kg). To ascertain the nature of interaction between TGB and VPA administered in combination, total brain concentrations of TGB and VPA were estimated by using high-performance liquid chromatography (HPLC) and fluorescence polarization immunoassay (FPIA).

RESULTS

TGB and VPA produced clear-cut anticonvulsant effects against PTZ-induced clonic seizures in mice and their DRRCs were not parallel to one another. The type I isobolographic analysis for non-parallel DRRCs revealed that the combination of TGB with VPA at the fixed-ratio of 1:1 exerted additive interaction against PTZ-induced clonic seizures in mice. With FPIA, it was found that TGB did not affect total brain VPA concentrations in experimental animals. Moreover, VPA had no significant impact on total brain concentrations of TGB in mice, as measured with HPLC.

CONCLUSION

The additive interaction between TGB and VPA at the fixed-ratio of 1:1 in the mouse PTZ model was pharmacodynamic in nature.

Interaction of pregabalin with carbamazepine in the mouse maximal electroshock-induced seizure model: a type I isobolographic analysis for non-parallel dose-response relationship curves

PURPOSE

To characterize the anticonvulsant effects of pregabalin (PGB - a third-generation antiepileptic drug) in combination with carbamazepine (CBZ - a classical antiepileptic drug) in the mouse maximal electroshock (MES)-induced seizure model by using the type I isobolographic analysis for non-parallel dose-response relationship curves (DRRCs).

MATERIAL/METHODS

Tonic hind limb extension (seizure activity) was evoked in adult male albino Swiss mice by a current (sine-wave, 25mA, 500V, 50Hz, 0.2s stimulus duration) delivered via auricular electrodes. Potential adverse-effect profiles of interaction of PGB with CBZ at the fixed-ratio of 1:1 in the MES test with respect to motor performance, long-term memory, skeletal muscular strength and antinociceptive activity were measured along with total brain CBZ concentrations.

RESULTS

In the mouse MES model, PGB administered singly had its DRRC non-parallel to that for CBZ. With type I isobolographic analysis for non-parallel DRRCs, the combination of PGB with CBZ at the fixed-ratio of 1:1 exerted additive interaction. In the combination, neither motor coordination, long-term memory nor muscular strength were affected. PGB administered alone and in combination with CBZ exerted antinociceptive effects, whereas CBZ administered alone produced no antinociceptive activity in mice subjected to the acute thermal pain model. Pharmacokinetic estimation of total brain antiepileptic drug concentrations revealed that PGB had no impact on total brain concentrations of CBZ in experimental animals.

CONCLUSIONS

In conclusion, the additive interaction between PGB and CBZ is worthy of consideration while extrapolating the results from this study to clinical settings.

Isobolographic characterization of interactions of levetiracetam with the various antiepileptic drugs in the mouse 6 Hz psychomotor seizure model

The aim of this study was to characterize the anticonvulsant effects of levetiracetam (LEV) in combination with the various antiepileptic drugs (clonazepam [CZP], oxcarbazepine [OXC], phenobarbital [PB], tiagabine [TGB], and valproate [VPA]), in the mouse 6 Hz psychomotor seizure model. Limbic (psychomotor) seizure activity was evoked in albino Swiss mice by a current (32 mA, 6 Hz, 3s stimulus duration) delivered via ocular electrodes and isobolographic analysis for parallel and non-parallel dose-response effects was used to characterize the consequent anticonvulsant interactions between the various drug combinations. Potential concurrent adverse-effect profiles of interactions between LEV and CZP, OXC, PB, TGB, and VPA at the fixed-ratio of 1:1 were evaluated in the chimney (motor performance), passive avoidance (long-term memory), and grip-strength (muscular strength) tests. LEV administered singly was associated with a dose-response relationship curve (DRRC) that was parallel to that for CZP and non-parallel to that for OXC, PB, TGB and VPA. With isobolography for parallel DRRCs, the combination of LEV with CZP at three fixed-ratios of 1:3, 1:1 and 3:1 was additive in nature. With isobolography for non-parallel DRRCs the combinations of LEV with OXC, TGB and VPA at the fixed-ratio of 1:1 were also additive. In contrast, the isobolography for non-parallel DRRCs revealed that the interaction for the combination of LEV with PB at the fixed-ratio of 1:1 was supra-additive (synergistic). None of the combinations were associated with any concurrent adverse effects with regards to motor coordination, long-term memory or muscular strength. LEV is associated with favorable anticonvulsant synergism with PB and is additive with regards to CZP, OXC, TGB and VPA in the mouse 6 Hz psychomotor seizure model.