Can roscovitine and trichostatin A be alternatives to standard protocols for cell cycle synchronization of ovine adult and foetal fibroblast cells?

Synchronization of donor cells is an important step for the success of somatic cell nuclear transfer application and facilitates the development of embryos. Contact inhibition, serum starvation and different chemical agents are used in synchronizing different types of somatic cells. In this study, to synchronize the primary ovine adult (POF) and foetal (POFF) fibroblast cells to G0/G1 phases, the contact inhibition, the serum starvation, roscovitine and trichostatin A (TSA) methods were used. In the first part of the study, roscovitine (10, 15, 20 and 30 μM) and TSA (25, 50, 75 and 100 nM) were applied for 24 h to determine the optimal concentration for POF and POFF cells. In the second part, optimal concentrations of roscovitine and TSA for these cells were compared with contact inhibition and serum starvation methods. Cell cycle distribution and apoptotic activity analysis were performed by flow cytometry to compare this synchronization methods. Serum starvation method resulted in higher cell synchronization rate in both cells compared to other groups. Although contact inhibition and TSA also achieved high success rates of synchronized cell value, it was observed that the difference between serum starvation and these groups was significant (p < .05). When the apoptosis rates of the two cell types were examined, it was observed that the early apoptotic cells in contact inhibition and late apoptotic cells in the serum starvation were higher than the other groups (p < .05). Although the 10 and 15 μM concentrations of roscovitine gave the lowest apoptosis rates, it was observed that it failed to synchronize both the ovine fibroblast cells to G0/G1 phase. As a result, it was concluded that while roscovitine was not successful to synchronize both the POFF and POF cell lines, TSA (50 nM for POF cells and 100 nM for POFF cells) can be used efficiently as an alternative to the contact inhibition and the serum starvation methods.

Effects of activation with a Ca ionophore and roscovitine on the development of human oocytes that failed to fertilize after ICSI

OBJECTIVE

The effects of oocyte activation with a Ca ionophore and roscovitine (Ca+R), a selective inhibitor of M-phase promoting factor, on unfertilized oocytes after intracytoplasmic sperm injection (ICSI) or testicular sperm extraction (TESE)-ICSI were evaluated.

METHOD

Oocytes without pronuclei at 18 hours after ICSI were judged to be unfertilized and were exposed to the Ca ionophore A23187 (5 ?M) with or without roscovitine (50 ?M). The activation rate was measured 3, 7, and 18 hours later. Oocytes with two polar bodies and two pronuclei with a sperm tail were judged to have been activated.

RESULTS

At 18 hours, the activation rates in the control, Ca ionophore, and Ca+R groups were 3.5% (4/112), 26.9% (7/26), and 32.1% (17/53), respectively. The activation rate of the Ca+R group was significantly higher than that of the control and similar to that of the Ca ionophore group. Among the oocytes that remained unfertilized after TESE-ICSI, the activation rates of the Ca ionophore and Ca+R groups were 22.2% (2/9) and 43.8% (7/16), respectively.

CONCLUSIONS

Sequential treatment with an Ca ionophore and roscovitine activates oocytes that remain unfertilized after ICSI. In TESE-ICSI, the activation rate tended to be increased by the co-administration of roscovitine with a Ca ionophore. J. Med. Invest. 70 : 321-324, August, 2023.

The Expression of Cell Cycle-Related Genes in USP8-Mutated Corticotroph Neuroendocrine Pituitary Tumors and Their Possible Role in Cell Cycle-Targeting Treatment

Protein deubiquitinases USP8 and USP48 are known driver genes in corticotroph pituitary neuroendocrine tumors (PitNETs). USP8 mutations have pleiotropic effects that include notable changes in genes' expression. Genes involved in cell cycle regulation were found differentially expressed in mutated and wild-type tumors. This study aimed to verify difference in the expression level of selected cell cycle-related genes and investigate their potential role in response to cell cycle inhibitors. Analysis of 70 corticotroph PitNETs showed that USP8-mutated tumors have lower CDKN1B, CDK6, CCND2 and higher CDC25A expression. USP48-mutated tumors have lower CDKN1B and CCND1 expression. A lower p27 protein level in mutated than in wild-type tumors was confirmed that may potentially influence the response to small molecule inhibitors targeting the cell cycle. We looked for the role of USP8 mutations or a changed p27 level in the response to palbociclib, flavopiridol and roscovitine in vitro using murine corticotroph AtT-20/D16v-F2 cells. The cells were sensitive to each agent and treatment influenced the expression of genes involved in cell cycle regulation. Overexpression of mutated Usp8 in the cells did not affect the expression of p27 nor the response to the inhibitors. Downregulating or upregulating p27 expression in AtT-20/D16v-F2 cells also did not affect treatment response.

Roscovitine Worsens Mycobacterium abscessus Infection by Reducing DUOX2-mediated Neutrophil Response

Persistent neutrophilic inflammation associated with chronic pulmonary infection causes progressive lung injury and, eventually, death in individuals with cystic fibrosis (CF), a genetic disease caused by biallelic mutations in the CF transmembrane conductance regulator (CFTR) gene. Therefore, we examined whether roscovitine, a cyclin-dependent kinase inhibitor that (in other conditions) reduces inflammation while promoting host defense, might provide a beneficial effect in the context of CF. Herein, using CFTR-depleted zebrafish larvae as an innovative vertebrate model of CF immunopathophysiology, combined with murine and human approaches, we sought to determine the effects of roscovitine on innate immune responses to tissue injury and pathogens in the CF condition. We show that roscovitine exerts antiinflammatory and proresolution effects in neutrophilic inflammation induced by infection or tail amputation in zebrafish. Roscovitine reduces overactive epithelial reactive oxygen species (ROS)-mediated neutrophil trafficking by reducing DUOX2/NADPH-oxidase activity and accelerates inflammation resolution by inducing neutrophil apoptosis and reverse migration. It is important to note that, although roscovitine efficiently enhances intracellular bacterial killing of Mycobacterium abscessus in human CF macrophages ex vivo, we found that treatment with roscovitine results in worse infection in mouse and zebrafish models. By interfering with DUOX2/NADPH oxidase-dependent ROS production, roscovitine reduces the number of neutrophils at infection sites and, consequently, compromises granuloma formation and maintenance, favoring extracellular multiplication of M. abscessus and more severe infection. Our findings bring important new understanding of the immune-targeted action of roscovitine and have significant therapeutic implications for safely targeting inflammation in CF.

Dibutyryl-cAMP and roscovitine differently affect premature meiotic resumption and embryo development of vitrified immature porcine oocytes

Vitrification and warming can trigger premature meiosis in immature porcine oocytes. Our aim was to compare the efficacies of two meiotic inhibitors, dibutyryl-cAMP and roscovitine for the meiosis synchronization during in vitro maturation (IVM) of porcine oocytes vitrified at the germinal vesicle (GV) stage. We first compared the efficacy of 1 mM dibutyryl-cAMP and 25 μM roscovitine on meiotic arrest during the first 22 h of IVM. Dibutyryl-cAMP could maintain the GV stage in 83.5% of oocytes; however, roscovitine was even more effective (96.6%), whereas only 17.4% of the oocytes remained at the GV stage without these additives. Temporal meiotic arrest for 22 h by roscovitine did not reduce the percentage of oocytes reaching the Metaphase II stage during subsequent IVM. However, after parthenogenetic stimulation or in vitro fertilization, subsequent embryo development to the blastocyst stage was compromised after roscovitine treatment, whereas dibutyryl-cAMP improved the percentage of blastocyst development. In conclusion, dibutyryl-cAMP could derogate but not completely prevent premature meiosis in vitrified oocytes, whereas roscovitine could more efficiently prevent it. However, for embryo production, the use of roscovitine was disadvantageous, whereas the use of dibutyryl-cAMP was beneficial.

CDK5 inhibition improves glucose uptake in insulin-resistant neuronal cells via ERK1/2 pathway

Role of CDK5 and its inhibition in various neuronal processes and functions are well established. However, role of CDK5 and its inhibition in neuronal insulin-signaling and-resistance is not yet explored. In the present study, we investigated the effect of CDK5 inhibition in neuronal insulin signaling, specifically insulin-stimulated glucose uptake. CDK5 expression in neuro-2a cells was increased under insulin-resistant state, developed by chronic treatment of insulin, confirming the crucial role of CDK5 in insulin resistance in neuronal cells. However, whether increased expression of CDK5 in hyperinsulinemia-mediated insulin-resistant conditions is a cause or a consequence, is still an unanswered question. We showed that CDK5 inhibition did not affect basal insulin signaling; however, insulin-stimulated glucose uptake enhanced in insulin-resistant cells. Moreover, CDK5 inhibition could improve glucose uptake, the ultimate outcome of insulin signaling, in insulin-resistant neuro-2a cells. We first time showed that CDK5 inhibition by roscovitine could ameliorate insulin resistance and increase glucose uptake in neuronal cells via ERK1/2 pathway. Our study provides intriguing insights about the effect of CDK5 inhibition on neuronal insulin resistance and opens up a new paradigm to develop new therapeutic strategies for neuronal insulin resistance and associated pathophysiological conditions.

Roscovitine, a Cyclin-Dependent Kinase-5 Inhibitor, Decreases Phosphorylated Tau Formation and Death of Retinal Ganglion Cells of Rats after Optic Nerve Crush

Tauopathies are neurodegenerative diseases characterized by abnormal metabolism of misfolded tau proteins and are progressive. Pathological phosphorylation of tau occurs in the retinal ganglion cells (RGCs) after optic nerve injuries. Cyclin-dependent kinase-5 (Cdk5) causes hyperphosphorylation of tau. To determine the roles played by Cdk5 in retinal degeneration, roscovitine, a Cdk5 inhibitor, was injected intravitreally after optic nerve crush (ONC). The neuroprotective effect of roscovitine was determined by the number of Tuj-1-stained RGCs on day 7. The change in the levels of phosphorylated tau, calpain-1, and cleaved α-fodrin was determined by immunoblots on day 3. The expression of P35/P25, a Cdk5 activator, in the RGCs was determined by immunohistochemistry. The results showed that roscovitine reduced the level of phosphorylated tau by 3.5- to 1.6-fold. Calpain-1 (2.1-fold) and cleaved α-fodrin (1.5-fold) were increased on day 3, suggesting that the calpain signaling pathway was activated. P35/P25 was accumulated in the RGCs that were poorly stained by Tuj-1. Calpain inhibition also reduced the increase in phosphorylated tau. The number of RGCs decreased from 2191 ± 178 (sham) to 1216 ± 122 cells/mm² on day 7, and roscovitine preserved the level at 1622 ± 130 cells/mm². We conclude that the calpain-mediated activation of Cdk5 is associated with the pathologic phosphorylation of tau.

Cyclin-dependent kinase inhibitor roscovitine attenuates liver inflammation and fibrosis by influencing initiating steps of liver injury

Liver diseases present a significant public health burden worldwide. Although the mechanisms of liver diseases are complex, it is generally accepted that inflammation is commonly involved in the pathogenesis. Ongoing inflammatory responses exacerbate liver injury, or even result in fibrosis and cirrhosis. Here we report that roscovitine, a cyclin-dependent kinase (CDK) inhibitor, exerts beneficial effects on acute and chronic liver inflammation as well as fibrosis. Animal models of lipopolysaccharide (LPS)/d-galactosamine- and acute or chronic CCl4-induced liver injury showed that roscovitine administration markedly attenuated liver injury, inflammation and histological damage in LPS/d-galactosamine- and CCl4-induced acute liver injury models, which is consistent with the results in vitro. RNA sequencing (RNA-seq) analysis showed that roscovitine treatment repressed the transcription of a broad set of pro-inflammatory genes involved in many aspects of inflammation, including cytokine production and immune cell proliferation and migration, and inhibited the TGF-β signaling pathway and the biological process of tissue remodeling. For further validation, the beneficial effect of roscovitine against inflammation was evaluated in chronic CCl4-challenged mice. The anti-inflammation effect of roscovitine was observed in this model, accompanied with reduced liver fibrosis. The anti-fibrotic mechanism involved inhibition of profibrotic genes and blocking of hepatic stellate cell (HSC) activation. Our data show that roscovitine administration protects against liver diseases through inhibition of macrophage inflammatory actions and HSC activation at the onset of liver injury.

Cellular and Molecular Mechanisms of R/S-Roscovitine and CDKs Related Inhibition under Both Focal and Global Cerebral Ischemia: A Focus on Neurovascular Unit and Immune Cells

Ischemic stroke is the second leading cause of death worldwide. Following ischemic stroke, Neurovascular Unit (NVU) inflammation and peripheral leucocytes infiltration are major contributors to the extension of brain lesions. For a long time restricted to neurons, the 10 past years have shown the emergence of an increasing number of studies focusing on the role of Cyclin-Dependent Kinases (CDKs) on the other cells of NVU, as well as on the leucocytes. The most widely used CDKs inhibitor, (R)-roscovitine, and its (S) isomer both decreased brain lesions in models of global and focal cerebral ischemia. We previously showed that (S)-roscovitine acted, at least, by modulating NVU response to ischemia. Interestingly, roscovitine was shown to decrease leucocytes-mediated inflammation in several inflammatory models. Specific inhibition of roscovitine majors target CDK 1, 2, 5, 7, and 9 showed that these CDKs played key roles in inflammatory processes of NVU cells and leucocytes after brain lesions, including ischemic stroke. The data summarized here support the investigation of roscovitine as a potential therapeutic agent for the treatment of ischemic stroke, and provide an overview of CDK 1, 2, 5, 7, and 9 functions in brain cells and leucocytes during cerebral ischemia.

Non-Linear Pharmacokinetics of Oral Roscovitine (Seliciclib) in Cystic Fibrosis Patients Chronically Infected with Pseudomonas aeruginosa: A Study on Population Pharmacokinetics with Monte Carlo Simulations

Roscovitine (Seliciclib), a new protein kinase inhibitor, was administered orally to adult patients with cystic fibrosis for the first time in the ROSCO-CF trial, a dose-escalation, phase IIa, randomized, controlled trial. Extensive pharmacokinetic sampling was performed up to 12 h after the first oral dose. Roscovitine and its main metabolite M3 were quantified by liquid chromatography coupled with tandem mass spectrometry. The pharmacokinetics analyses were performed by non-linear mixed effects modelling. Monte Carlo simulations were performed to assess the impact of dose on the pharmacokinetics of oral roscovitine. Twenty-three patients received oral doses ranging from 200 to 800 mg of roscovitine and 138 data points were available for both roscovitine and M3 concentrations. The pharmacokinetics was best described by a two-compartment parent-metabolite model, with a complex saturable absorption process modelled as the sum of Gaussian inverse density functions. The Monte Carlo simulations showed a dose-dependent and saturable first-pass effect leading to pre-systemic formation of M3. The treatment with proton-pump inhibitors reduced the rate of absorption of oral roscovitine. The pharmacokinetics of oral roscovitine in adult patients with cystic fibrosis was non-linear and showed significant inter-individual variability. A repeat-dose study will be required to assess the inter-occasional variability of its pharmacokinetics.

Long Noncoding RNA H19 Induces Neuropathic Pain by Upregulating Cyclin-Dependent Kinase 5-Mediated Phosphorylation of cAMP Response Element Binding Protein

Objective

Neuropathic pain (NP) is a debilitating condition caused by nervous system injury and chronic diseases. LncRNA H19 is upregulated in many human diseases, including NP. Cyclin-dependent kinase 5 (CDK5) aggressively worsens inflammatory action and nerve damage to cause severe NP. Phosphorylated cAMP response element binding protein (CREB) is detrimental to nerves and promotes NP progression. Herein, aim of our study was to assess the mechanism of lncRNA H19.

Methods

The NP rat model was established using chronic constriction injury (CCI). Paw withdrawal threshold (PWT) tests and paw withdrawal latency (PWL) tests were performed. Then, small interfering (si)RNA against H19 was intrathecally injected into rats to suppress H19 expression. Schwann cells were isolated from NP rats and transfected with siRNA-H19 or a lentivirus (LV)-based vector expressing H19. Inflammatory factors and glial fibrillary acidic protein (GFAP) were detected. Western blot analysis was conducted to detect CDK5/p35 and p-CREB expression. Finally, H19, CDK5 and CREB phosphorylation were tested with the combination of the CDK5 inhibitor roscovitine and transfection of LV-H19 and siRNA-H19. Finally, we investigated the binding relationships between H19 and miR-196a-5p and between miR-196a-5p and CDK5 and detected the mRNA expression of miR-196a-5p and CDK5 in rats with H19 knockdown and in Schwann cells with H19 knockdown.

Results

Highly expressed H19, CDK5/p-35 and p-CREB were observed in NP rats, accompanied by obviously decreased PWT and PWL, upregulated inflammatory factors and GFAP levels, and reduced 5-HT_2A and GABA_B2 expression. siRNA-H19 restored NP-related indexes and downregulated CDK5/p35 and p-CREB phosphorylation. siRNA-H19, together with the CDK5 inhibitor roscovitine, reduced CDK5 and p-CREB expression in Schwann cells isolated from NP rats. Binding sites between H19 and miR-196a-5p and between miR-196a-5p and CDK5 were identified. Silencing H19 upregulated miR-196a-5p expression and downregulated CDK5 levels.

Conclusion

Our study demonstrated that silencing H19 inhibited NP by suppressing CDK5/p35 and p-CREB phosphorylation via the miR-196a-5p/CDK5 axis, which may provide new insight into NP treatment.

The Effect of Novel 7-methyl-5-phenyl-pyrazolo[4,3-e]tetrazolo[4,5-b][1,2,4]triazine Sulfonamide Derivatives on Apoptosis and Autophagy in DLD-1 and HT-29 Colon Cancer Cells

The discovery of cytotoxic drugs is focused on designing a compound structure that directly affects cancer cells without an impact on normal cells. The mechanism of anticancer activity is mainly related with activation of apoptosis. However, recent scientific reports show that autophagy also plays a crucial role in cancer cell progression. Thus, the objective of this study was to synthesize 7-methyl-5-phenyl-pyrazolo[4,3-e]tetrazolo[4,5-b][1,2,4]triazine utilizing nucleophilic substitution reaction at the position N1. The biological activity of tested compounds was assessed in DLD-1 and HT-29 cell lines. The induction of apoptosis was confirmed by Annexin V binding assay and acridine orange/ethidium bromide staining. The loss of mitochondrial membrane potential and caspase-8 activity was estimated using cytometer flow analysis. The concentration of p53, LC3A, LC3B and beclin-1 was measured using the ELISA technique. Our study revealed that anticancer activity of 7-methyl-5-phenyl-pyrazolo[4,3-e]tetrazolo[4,5-b][1,2,4]triazine derivatives is related with initiation of apoptosis occur on the intrinsic pathway with mitochondrial membrane decrease and extrinsic with increase of activity of caspase-8. Moreover, a decrease in beclin-1, LC3A, and LC3B were observed in two cell lines after treatment with novel compounds. This study showed that novel 7-methyl-5-phenyl-pyrazolo[4,3-e]tetrazolo[4,5-b][1,2,4]triazine derivatives might be a potential strategy in colon cancer treatment.

Roscovitine enhances all-trans retinoic acid (ATRA)-induced nuclear enrichment of an ensemble of activated signaling molecules and augments ATRA-induced myeloid cell differentiation

Although ATRA represents a successful differentiation therapy for APL, it is largely ineffective for non-APL AMLs. Hence combination therapies using an agent targeting ATRA-regulated molecules that drive cell differentiation/arrest are of interest. Using the HL-60 human non-APL AML model where ATRA causes nuclear enrichment of c-Raf that drives differentiation/G0-arrest, we now observe that roscovitine enhanced nuclear enrichment of certain traditionally cytoplasmic signaling molecules and enhanced differentiation and cell cycle arrest. Roscovitine upregulated ATRA-induced nuclear c-Raf phosphorylation at S259 and S289/296/301. Nuclear c-Raf interacted with RB protein and specifically with pS608RB, the hinge region phosphorylation controlling E2F binding and cell cycle progression. ATRA-induced loss of pS608RB with cell cycle arrest was associated with loss of RB-sequestered c-Raf, thereby coupling cell cycle arrest and increased availability of c-Raf to promote differentiation. Part of this mechanism reflects promoting cell cycle arrest via ATRA-induced upregulation of the p27 Kip1 CDKI. Roscovitine also enhanced the ATRA-induced nuclear enrichment of other signaling molecules traditionally perceived as cytoplasmic promoters of proliferation, but now known to promote differentiation; in particular: SFKs, Lyn, Fgr; adaptor proteins, c-Cbl, SLP-76; a guanine exchange factor, Vav1; and a transcription factor, IRF-1. Akin to c-Raf, Lyn bound to RB, specifically to pS608RB. Lyn-pS608RB association was greatly diminished by ATRA and essentially lost in ATRA plus roscovitine treated cells. Interestingly Lyn-KD enhanced such ATRA-induced nuclear signaling and differentiation and made roscovitine more effective. ATRA thus mobilized traditionally cytoplasmic signaling molecules to the nucleus where they drove differentiation which were further enhanced by roscovitine.

Meiotic block with roscovitine improves competence of porcine oocytes by fine-tuning activities of different cyclin-dependent kinases

Successful use of oocytes from small follicles (SFs) is of great importance for animal embryo production and human in vitro fertilization with reduced hormone-related side effects. How in vitro meiotic arrest maintenance (MAM) increases the competence of oocytes is not clear. In this study, pig oocytes recovered from SF of 1-2 mm and medium-follicles (MF) of 3-6 mm in diameter from abattoir ovaries were treated by various MAM treatments to improve their competence. The results showed that 25 µM roscovitine or 1 mM db-cAMP efficiently blocked germinal vesicle breakdown in both SF and MF oocytes suggesting a similar cyclin-dependent kinase (CDK) 1 level between the two oocyte groups. MAM with 15- and 25-µM roscovitine alone or with 1-mM db-cAMP improved competence of SF and MF oocytes, respectively, with a promoted chromatin configuration transition from surrounded nucleoli (SN) to re-decondensation (RDC) pattern that supported substantial gene transcription. However, MAM with db-cAMP alone or with higher concentrations of roscovitine did not improve oocyte competence, could not support an SN-to-RDC transition, and/or evoked a premature chromatin condensation (PMC) that suppressed gene transcription. Both CDK2 and CDK5 contents were higher (p < .05) in MF than in SF oocytes. It is concluded that the competence of pig oocytes, particularly that of SF oocytes can be improved by MAM using a proper roscovitine concentration that promotes gene transcription by inhibiting CDK5 while letting CDK2 off to prevent PMC.

Effect of roscovitine on developmental competence of small follicle-derived buffalo oocytes

Background & objectives:

The lower recovery of competent oocytes in buffalo species limits the commercialization of in vitro embryo production technology in field condition. In this context, pre-maturation of small follicle (SF)-derived oocytes with meiotic inhibition may be a promising alternative to obtain more number of competent oocytes. Thus, the present study was conducted with an objective to enhance the developmental potential of less competent SF-derived buffalo oocytes.

Methods:

All the visible follicles (used for aspiration) from buffalo ovaries were divided into two categories: large follicle (LF) (follicles having diameter ≥6 mm) and SF (follicles of diameter <6 mm). The competence of LF and SF oocytes was observed in terms of brilliant cresyl blue (BCB) staining, cleavage rate, blastocyst rate and relative gene expression of oocyte and blastocyst competence markers. Thereafter, less competent SF oocytes were treated with 0, 12.5, 25, 50 and 100 mM doses of roscovitine (cyclin-dependent kinase inhibitor) to enhance their developmental potential.

Results:

Based on parameters studied, LF oocytes were found to be more competent than SF oocytes. Pre-maturation incubation of SF oocytes with roscovitine reversibly arrested oocyte maturation for 24 h to ensure the proper maturation of less competent oocytes. A significantly higher number of BCB-positive oocytes were noted in roscovitine-treated group than SF group. Cleavage and blastocyst rates were also higher in roscovitine-treated group. The relative messenger RNA expression of oocyte (GDF9, BMP15, GREM1, EGFR, PTGS2 and HAS2) as well as blastocyst (INF-τ, GLUT1 and POU5F1) competence markers was significantly greater in roscovitine-treated group relative to SF group. Again, on comparison with LF group, these parameters depicted a lower value in the treatment group.

Interpretation & conclusions:

The findings of this study has revealed that pre-maturation incubation of SF-derived oocytes with 25 μM roscovitine can improve its developmental competence and thus can be utilized to get maximum number of competent oocytes for better commercialization of in vitro embryo production technology in buffalo.

Novel Pyrazolo[3,4-d]pyrimidines as Potential Cytotoxic Agents: Design, Synthesis, Molecular Docking and CDK2 Inhibition

BACKGROUND

Pyrazolo[3,4-d]pyrimidine scaffold was reported to possess potent cytotoxic and CDK2 inhibitory activity as analogue of roscovitine.

OBJECTIVE

To design and synthesize novel 1-(4-flourophenyl)pyrazolo[3,4-d]pyrimidine derivatives as bioisosters of roscovitine with potential cytotoxic and CDK2 inhibitory activity.

METHODS

A series of novel 1-(4-flourophenyl)pyrazolo[3,4-d]pyrimidines were designed and synthesized. Structural elucidation for all the newly synthesized compounds was achieved through performing MS, ¹H NMR, ¹³C NMR and IR spectral techniques. Eight compounds were screened for their cytotoxic activity by National Cancer Institute (USA) against 60 different human cancer cell lines. Compounds 2a, 4, 6, 7b, 8a and 8b were further studied through the determination of their IC₅₀ values against the most sensitive cell lines. The inhibitory activities of compounds 2a and 4 were evaluated against CDK2 enzyme.

RESULTS

Compound 4 exhibited the most prominent broad-spectrum cytotoxic activity against 42 cell lines representing all human cancer types showing growth inhibition percentages from 53.19 to 99.39. Compound 2a showed promising selectivity against several cell lines. Moreover, all the test compounds exhibited potent cytotoxic activity in nanomolar to micromolar range with IC₅₀ values ranging from 0.58 to 8.32μM. Compound 2a showed significant cytotoxic activity against CNS (SNB-75), lung (NCI-H460) and ovarian (OVCAR-4) cancer cell lines with IC₅₀ values 0.64, 0.78 and 1.9μM, respectively. Compound 4 showed promising potency against leukemia (HL-60) and CNS (SNB-75) cell lines (IC₅₀ = 0.58 and 0.94μM, sequentially). Moreover, the antiproliferative activities of compounds 2a and 4 appeared to correlate well with their ability to inhibit CDK2 at sub-micromolar level (IC₅₀ = 0.69 and 0.67μM, respectively) that were comparable to roscovitine (IC₅₀=0.44μM). The Molecular docking results revealed that compound 4 interacted with the same key amino acids as roscovitine in the active site of CDK2 enzyme with a marked docking score (-14.1031 kcal/mol).

CONCLUSION

1-(4-Flourophenyl)pyrazolo[3,4-d]pyrimidine is a promising scaffold for the design and synthesis of potent cytotoxic leads.

Novel Mouse Tauopathy Model for Repetitive Mild Traumatic Brain Injury: Evaluation of Long-Term Effects on Cognition and Biomarker Levels After Therapeutic Inhibition of Tau Phosphorylation

Traumatic brain injury (TBI) is a risk factor for a group of neurodegenerative diseases termed tauopathies, which includes Alzheimer's disease and chronic traumatic encephalopathy (CTE). Although TBI is stratified by impact severity as either mild (m), moderate or severe, mTBI is the most common and the most difficult to diagnose. Tauopathies are pathologically related by the accumulation of hyperphosphorylated tau (P-tau) and increased total tau (T-tau). Here we describe: (i) a novel human tau-expressing transgenic mouse model, TghTau/PS1, to study repetitive mild closed head injury (rmCHI), (ii) quantitative comparison of T-tau and P-tau from brain and plasma in TghTau/PS1 mice over a 12 month period following rmCHI (and sham), (iii) the usefulness of P-tau as an early- and late-stage blood-based biochemical biomarker for rmCHI, (iii) the influence of kinase-targeted therapeutic intervention on rmCHI-associated cognitive deficits using a combination of lithium chloride (LiCl) and R-roscovitine (ros), and (iv) correlation of behavioral and cognitive changes with concentrations of the brain and blood-based T-tau and P-tau. Compared to sham-treated mice, behavior changes and cognitive deficits of rmCHI-treated TghTau/PS1 mice correlated with increases in both cortex and plasma T-tau and P-tau levels over 12 months. In addition, T-tau, but more predominantly P-tau, levels were significantly reduced in the cortex and plasma by LiCl + ros approaching the biomarker levels in sham and drug-treated sham mice (the drugs had only modest effects on the T-tau and P-tau levels in sham mice) throughout the 12 month study period. Furthermore, although we also observed a reversal of the abnormal behavior and cognitive deficits in the drug-treated rmCHI mice (compared to the untreated rmCHI mice) throughout the time course, these drug-treated effects were most pronounced up until 10 and 12 months where the abnormal behavior and cognition deficits began to gradually increase. These studies describe: (a) a translational relevant animal model for TBI-linked tauopathies, and (b) utilization of T-tau and P-tau as rmCHI biomarkers in plasma to monitor novel therapeutic strategies and treatment regimens for these neurodegenerative diseases.

KHC-4 inhibits β-catenin expression in prostate cancer cells

KHC-4 is a 2-phenyl-4-quinolone analogue that exhibits anticancer activity. Aberrant activation of β-catenin signaling contributes to prostate cancer development and progression. Therefore, targeting β-catenin expression could be a useful approach to treating prostate cancer. We found that KHC-4 can inhibit β-catenin expression and its signaling pathway in DU145 prostate cancer cells. Treatment with KHC-4 decreased total β-catenin expression and concomitantly decreased β-catenin levels in both the cytoplasm and nucleus of cells. KHC-4 treatment also inhibited β-catenin expression and that of its target proteins, PI3K, AKT, GSK3β and TBX3. We monitored the stability of β-catenin with the proteasomal inhibitor, MG132, in DU145 cells and found that MG132 reversed KHC-4-induced proteasomal β-catenin degradation. We verified CDK1/β-catenin expression in KHC-4 treated DU145 cells. We found that roscovitine treatment reversed cell proliferation by arresting the cell cycle at the G2/M phase and β-catenin expression caused by KHC-4 treatment. We suggest that KHC-4 inhibits β-catenin signaling in DU145 prostate cancer cells.

Nucleocytoplasmic p27Kip1 Export Is Required for ERK1/2-Mediated Reactive Astroglial Proliferation Following Status Epilepticus

Reactive astrogliosis is a prominent and ubiquitous reaction of astrocytes to many types of brain injury. Up-regulation of glial fibrillary acidic protein (GFAP) expression and astroglial proliferation are hallmarks of reactive astrogliosis. However, the mechanisms that regulate reactive astrogliosis remain elusive. In the present study, status epilepticus (SE, a prolonged seizure activity) led to reactive astrogliosis showing the increases in GFAP expression and the number of proliferating astrocytes with prolonged extracellular signal receptor-activated kinases 1/2 (ERK1/2) activation and reduced nuclear p27^Kip1 level. U0126, an ERK1/2 inhibitor, showed opposite effects. Leptomycin B (LMB), an inhibitor of chromosomal maintenance 1 (CRM1), attenuated nucleocytoplasmic p27^Kip1 export and astroglial proliferation, although it up-regulated ERK1/2 phosphorylation and GFAP expression. Roscovitine ameliorated the reduced nuclear p27^Kip1 level and astroglial proliferation without changing GFAP expression and ERK1/2 phosphorylation. U0126 aggravated SE-induced astroglial apoptosis in the molecular layer of the dentate gyrus that was unaffected by LMB and roscovitine. In addition, U0126 exacerbated SE-induced neuronal death, while LMB mitigated it. Roscovitine did not affect SE-induced neuronal death. The present data elucidate for the first time the roles of nucleocytoplasmic p27^Kip1 transport in ERK1/2-mediated reactive astrogliosis independent of SE-induced neuronal death and astroglial apoptosis. Therefore, our findings suggest that nucleocytoplasmic p27^Kip1 export may be required for ERK1/2-mediated astroglial proliferation during reactive astrogliosis, and that nuclear p27^Kip1 entrapment may be a potential therapeutic strategy for anti-proliferation in reactive astrocytes.

Casein kinase 1ε and 1α as novel players in polycystic kidney disease and mechanistic targets for (R)-roscovitine and (S)-CR8

Following the discovery of (R)-roscovitine's beneficial effects in three polycystic kidney disease (PKD) mouse models, cyclin-dependent kinases (CDKs) inhibitors have been investigated as potential treatments. We have used various affinity chromatography approaches to identify the molecular targets of roscovitine and its more potent analog (S)-CR8 in human and murine polycystic kidneys. These methods revealed casein kinases 1 (CK1) as additional targets of the two drugs. CK1ε expression at the mRNA and protein levels is enhanced in polycystic kidneys of 11 different PKD mouse models as well as in human polycystic kidneys. A shift in the pattern of CK1α isoforms is observed in all PKD mouse models. Furthermore, the catalytic activities of both CK1ε and CK1α are increased in mouse polycystic kidneys. Inhibition of CK1ε and CK1α may thus contribute to the long-lasting attenuating effects of roscovitine and (S)-CR8 on cyst development. CDKs and CK1s may constitute a dual therapeutic target to develop kinase inhibitory PKD drug candidates.

Selective antitumor activity of roscovitine in head and neck cancer

Radiation and chemotherapy that are commonly used to treat human cancers damage cellular DNA. DNA damage appears to be more toxic to cancer cells than normal cells, most likely due to deregulated checkpoint activation and/or deficiency in DNA repair pathways that are characteristics of many tumors. However, unwanted side effects arise as a result of DNA damage to normal cells during the treatment.

Here, we show that roscovitine, a cyclin-dependent kinase (CDK) inhibitor that inhibits CDK-1, CDK-2, CDK-5, CDK-7, and CDK-9 due to competitive binding to the ATP site on the kinases, causes significant DNA damage followed by p53-dependent cell death in human papilloma virus (HPV)-positive, but not in HPV-negative, head and neck cancer cells. Since HPV positivity was a molecular marker for increased sensitivity of cells to roscovitine, we reasoned that systemic roscovitine administration would not be toxic to healthy HPV-negative tissue. Indeed, low roscovitine doses significantly inhibited the growth of HPV-associated xenografted tumors in mice without causing any detectable side effects.

Given that inhibition of CDKs has been shown to inhibit replication of several viruses, we suggest that roscovitine treatment may represent a selective and safe targeted therapeutic option against HPV-positive head and neck cancer.

Pituitary-Directed Therapies for Cushing's Disease

Cushing's disease (CD) is caused by a pituitary corticotroph neuroendocrine tumor inducing uncontrolled hypercortisolism. Transsphenoidal surgery is the first-line treatment in most cases. Nonetheless, some patients will not achieve cure even in expert hands, others may not be surgical candidates and a significant percentage will experience recurrence. Many patients will thus require medical therapy to achieve disease control. Pharmacologic options to treat CD have increased in recent years, with an explosion in knowledge related to pathophysiology at the molecular level. In this review, we focus on medications targeting specifically pituitary adrenocorticotropic hormone-secreting tumors. The only medication in this group approved for the treatment of CD is pasireotide, a somatostatin receptor ligand. Cabergoline and temozolomide may also be used in select cases. Previously studied and abandoned medical options are briefly discussed, and emphasis is made on upcoming medications. Mechanism of action and available data on efficacy and safety of cell cycle inhibitor roscovitine, epidermal growth factor receptor inhibitor gefitinib, retinoic acid, and silibinin, a heat shock protein 90 inhibitor are also presented.

HNSCC cell lines

At present, advanced stage human Papillomavirus (HPV) negative and positive head and neck squamous cell carcinoma (HNSCC) are treated by intense multimodal therapy that includes radiochemotherapy, which are associated with relevant side effects. Patients with HPV positive tumors possess a far better prognosis than those with HPV negative cancers. Therefore, new therapeutic strategies are needed to improve the outcome especially of the latter one as well as quality of life for all HNSCC patients. Here we tested whether roscovitine, an inhibitor of cyclin-dependent kinases (CDKs), which hereby also blocks homologous recombination (HR), can be used to enhance the radiation sensitivity of HNSCC cell lines.

In all five HPV negative and HPV positive cell lines tested, roscovitine caused inhibition of CDK1 and 2. Surprisingly, all HPV positive cell lines were found to be defective in HR. In contrast, HPV negative strains demonstrated efficient HR, which was completely suppressed by roscovitine. In line with this, for HPV negative but not for HPV positive cell lines, treatment with roscovitine resulted in a pronounced enhancement of the radiation-induced G2 arrest as well as a significant increase in radiosensitivity. Due to a defect in HR, all HPV positive cell lines were efficiently radiosensitized by the PARP-1 inhibitor olaparib. In contrast, in HPV negative cell lines a significant radiosensitization by olaparib was only achieved when combined with roscovitine.

p47Phox/CDK5/DRP1-Mediated Mitochondrial Fission Evokes PV Cell Degeneration in the Rat Dentate Gyrus Following Status Epilepticus

Parvalbumin (PV) is one of the calcium-binding proteins, which plays an important role in the responsiveness of inhibitory neurons to an adaptation to repetitive spikes. Furthermore, PV neurons are highly vulnerable to status epilepticus (SE, prolonged seizure activity), although the underlining mechanism remains to be clarified. In the present study, we found that p47Phox expression was transiently and selectively increased in PV neurons 6 h after SE. This up-regulated p47Phox expression was accompanied by excessive mitochondrial fission. In this time point, CDK5-tyrosine 15 and dynamin-related protein 1 (DRP1)-serine 616 phosphorylations were also increased in PV cells. Apocynin (a p47Phox inhibitor) effectively mitigated PV cell loss via inhibition of CDK5/DRP1 phosphorylations and mitochondrial fragmentation induced by SE. Roscovitine (a CDK5 inhibitor) and Mdivi-1 (a DRP1 inhibitor) attenuated SE-induced PV cell loss by inhibiting aberrant mitochondrial fission. These findings suggest that p47Phox/CDK5/DRP1 may be one of the important upstream signaling pathways in PV cell degeneration induced by SE via excessive mitochondrial fragmentation.

Harnessing Neutrophil Survival Mechanisms during Chronic Infection by Pseudomonas aeruginosa: Novel Therapeutic Targets to Dampen Inflammation in Cystic Fibrosis

More than two decades after cloning the cystic fibrosis transmembrane regulator (CFTR) gene, the defective gene in cystic fibrosis (CF), we still do not understand how dysfunction of this ion channel causes lung disease and the tremendous neutrophil burden which persists within the airways; nor why chronic colonization by Pseudomonas aeruginosa develops in CF patients who are thought to be immunocompetent. It appears that the microenvironment within the lung of CF patients provides favorable conditions for both P. aeruginosa colonization and neutrophil survival. In this context, the ability of bacteria to induce hypoxia, which in turn affects neutrophil survival is an additional level of complexity that needs to be accounted for when controlling neutrophil fate in CF. Recent studies have underscored the importance of neutrophils in innate immunity and their functions appear to extend far beyond their well-described role in antibacterial defense. Perhaps a disturbance in neutrophil reprogramming during the course of an infection severely modulates the inflammatory response in CF. Furthermore there is an emerging concept that the CFTR itself may be an immune modulator and stimulating CFTR function in CF patients could promote neutrophil and macrophages antimicrobial function. Fostering the resolution of inflammation by favoring neutrophil apoptosis could preserve their microbicidal activities but decrease their proinflammatory potential. In this context, triggering neutrophil apoptosis with roscovitine may be a potential therapeutic option and this is currently being evaluated in CF patients. In the present review we discuss how neutrophils functions are disturbed in CF and how this may relate to chronic infection with P. aeuginosa and we propose novel research directions aimed at modulating neutrophil survival, dampening lung inflammation and ultimately leading to an amelioration of the lung disease.

Acute stress regulates phosphorylation of N-methyl-d-aspartate receptor GluN2B at S1284 in hippocampus

Exposure to acute stress leads to diverse changes, which include either beneficial or deleterious effects on molecular levels that are implicated in stress-related disorders. N-methyl-d-aspartate receptor (NMDAR)-mediated signalings, are thought to be vital players in stress-related mental disorders as well as attractive therapeutic targets for clinical treatment. In the present study, we utilized acute stress models in mice to explore regulation of phosphorylation level of S1284 in GluN2B subunit of NMDAR. We found out that forced swimming and acute restraint stress increased phosphorylation level of S1284, while phosphorylation level of S1284 was unaltered after brief exposure to open field. Moreover, phosphorylation change of S1284 was negated by treatment of roscovitine which is believed to be a Cyclin-dependent kinase inhibitor. Besides, we showed well correlation of phosphorylation change of S1284 and immobility time during forced swimming. Collectively, our results demonstrated that phosphorylation level of S1284 in GluN2B was regulated by acute stress.

Roscovitine protects murine Leydig cells from lipopolysaccharide-induced inflammation

Roscovitine is a cyclin-dependent kinase inhibitor, which has been previously investigated for its anticancer effects. It has also been confirmed that roscovitine can downregulate the expression of myeloid cell leukemia-1 protein to inhibit inflammation. In the present study, roscovitine was used to treat inflammation in lipopolysaccharide (LPS)-induced model mice. At the cellular level, Leydig cells isolated from mouse testis were assessed for inflammatory factors. It was revealed that roscovitine successfully reduced inflammation-associated injury induced by LPS pretreatment. At the molecular level, roscovitine was found to exert this effect through promotion of adenosine monophosphate-activated protein kinase phosphorylation. To the best of our knowledge, the present study was the first to suggest that roscovitine has a protective role in Leydig cells through its anti-inflammatory action.

Enhanced Late Na and Ca Currents as Effective Antiarrhythmic Drug Targets

While recent advances clarified the molecular and cellular modes of action of antiarrhythmic drugs (AADs), their link to suppression of dynamical arrhythmia mechanisms remains only partially understood. The current classifications of AADs (Classes I, III, and IV) rely on blocking peak Na, K and L-type calcium currents (I_Ca,L), with Class II with dominant beta receptor blocking activity and Class V including drugs with diverse classes of actions. The discovery that the calcium and redox sensor, cardiac Ca/calmodulin-dependent protein kinase II (CaMKII) enhances both the late Na (I_Na-L) and the late I_Ca,L in patients at high risk of VT/VF provided a new and a rational AAD target. Pathological rise of either or both of I_Na-L and late I_Ca,L are demonstrated to promote cellular early afterdepolarizations (EADs) and EAD-mediated triggered activity that can initiate VT/VF in remodeled hearts. Selective inhibition of the I_Na-L without affecting their peak transients with the highly specific prototype drug, GS-967 suppresses these EAD-mediated VT/VFs. As in the case of I_Na-L, selective inhibition of the late I_Ca,L without affecting its peak with the prototype drug, roscovitine suppressed oxidative EAD-mediated VT/VF. These findings indicate that specific blockers of the late inward currents without affecting their peaks (gating modifiers), offer a new and effective AAD class action i.e., “Class VI.” The development of safe drugs with selective Class VI actions provides a rational and effective approach to treat VT/VF particularly in cardiac conditions associated with enhanced CaMKII activity such as heart failure.

TRPC6 channel translocation into phagosomal membrane augments phagosomal function

Defects in the innate immune system in the lung with attendant bacterial infections contribute to lung tissue damage, respiratory insufficiency, and ultimately death in the pathogenesis of cystic fibrosis (CF). Professional phagocytes, including alveolar macrophages (AMs), have specialized pathways that ensure efficient killing of pathogens in phagosomes. Phagosomal acidification facilitates the optimal functioning of degradative enzymes, ultimately contributing to bacterial killing. Generation of low organellar pH is primarily driven by the V-ATPases, proton pumps that use cytoplasmic ATP to load H(+) into the organelle. Critical to phagosomal acidification are various channels derived from the plasma membrane, including the anion channel cystic fibrosis transmembrane conductance regulator, which shunt the transmembrane potential generated by movement of protons. Here we show that the transient receptor potential canonical-6 (TRPC6) calcium-permeable channel in the AM also functions to shunt the transmembrane potential generated by proton pumping and is capable of restoring microbicidal function to compromised AMs in CF and enhancement of function in non-CF cells. TRPC6 channel activity is enhanced via translocation to the cell surface (and then ultimately to the phagosome during phagocytosis) in response to G-protein signaling activated by the small molecule (R)-roscovitine and its derivatives. These data show that enhancing vesicular insertion of the TRPC6 channel to the plasma membrane may represent a general mechanism for restoring phagosome activity in conditions, where it is lost or impaired.

Roscovitine in cancer and other diseases

Roscovitine [CY-202, (R)-Roscovitine, Seliciclib] is a small molecule that inhibits cyclin-dependent kinases (CDKs) through direct competition at the ATP-binding site. It is a broad-range purine inhibitor, which inhibits CDK1, CDK2, CDK5 and CDK7, but is a poor inhibitor for CDK4 and CDK6. Roscovitine is widely used as a biological tool in cell cycle, cancer, apoptosis and neurobiology studies. Moreover, it is currently evaluated as a potential drug to treat cancers, neurodegenerative diseases, inflammation, viral infections, polycystic kidney disease and glomerulonephritis. This review focuses on the use of roscovitine in the disease model as well as clinical model research.

Cyclin-dependent kinase 5 regulates degranulation in human eosinophils

Degranulation from eosinophils in response to secretagogue stimulation is a regulated process that involves exocytosis of granule proteins through specific signalling pathways. One potential pathway is dependent on cyclin-dependent kinase 5 (Cdk5) and its effector molecules, p35 and p39, which play a central role in neuronal cell exocytosis by phosphorylating Munc18, a regulator of SNARE binding. Emerging evidence suggests a role for Cdk5 in exocytosis in immune cells, although its role in eosinophils is not known. We sought to examine the expression of Cdk5 and its activators in human eosinophils, and to assess the role of Cdk5 in eosinophil degranulation. We used freshly isolated human eosinophils and analysed the expression of Cdk5, p35, p39 and Munc18c by Western blot, RT-PCR, flow cytometry and immunoprecipitation. Cdk5 kinase activity was determined following eosinophil activation. Cdk5 inhibitors were used (roscovitine, AT7519 and small interfering RNA) to determine its role in eosinophil peroxidase (EPX) secretion. Cdk5 was expressed in association with Munc18c, p35 and p39, and phosphorylated following human eosinophil activation with eotaxin/CCL11, platelet-activating factor, and secretory IgA-Sepharose. Cdk5 inhibitors (roscovitine, AT7519) reduced EPX release when cells were stimulated by PMA or secretory IgA. In assays using small interfering RNA knock-down of Cdk5 expression in human eosinophils, we observed inhibition of EPX release. Our findings suggest that in activated eosinophils, Cdk5 is phosphorylated and binds to Munc18c, resulting in Munc18c release from syntaxin-4, allowing SNARE binding and vesicle fusion, with subsequent eosinophil degranulation. Our work identifies a novel role for Cdk5 in eosinophil mediator release by agonist-induced degranulation.

The effect of circadian rhythm on pharmacokinetics and metabolism of the Cdk inhibitor, roscovitine, in tumor mice model

Roscovitine is a selective Cdk-inhibitor that is under investigation in phase II clinical trials under several conditions, including chemotherapy. Tumor growth inhibition has been previously shown to be affected by the dosing time of roscovitine in a Glasgow osteosarcoma xenograft mouse model. In the current study, we examined the effect of dose timing on the pharmacokinetics, biodistribution and metabolism of this drug in different organs in B6D2F1 mice. The drug was orally administered at resting (ZT3) or activity time of the mice (ZT19) at a dose of 300 mg/kg. Plasma and organs were removed at serial time points (10, 20 and 30 min; 1, 2, 4, 6, 8, 12 and 24 h) after the administration. Roscovitine and its carboxylic metabolite concentrations were analyzed using HPLC-UV, and pharmacokinetic parameters were calculated in different organs. We found that systemic exposure to roscovitine was 38% higher when dosing at ZT3, and elimination half-life was double compared to when dosing at ZT19. Higher organ concentrations expressed as (organ/plasma) ratio were observed when dosing at ZT3 in the kidney (180%), adipose tissue (188%), testis (132%) and lungs (112%), while the liver exposure to roscovitine was 120% higher after dosing at ZT19. The metabolic ratio was approximately 23% higher at ZT19, while the intrinsic clearance (CLint) was approximately 67% higher at ZT19, indicating faster and more efficient metabolism. These differences may be caused by circadian differences in the absorption, distribution, metabolism and excretion processes governing roscovitine disposition in the mice. In this article, we describe for the first time the chronobiodistribution of roscovitine in the mouse and the contribution of the dosing time to the variability of its metabolism. Our results may help in designing better dosing schedules of roscovitine in clinical trials.

Cell cycle analysis and interspecies nuclear transfer of cat cells treated with chemical inhibitors

This study investigated the effect of chemical inhibitors on the cell-cycle synchronisation in cat fibroblast cells and evaluated the development of interspecies embryos reconstructed from cat donor cells and enucleated bovine oocytes. Cat fibroblast cells were treated with 15 μg/mL roscovitine or 0.05 μg/mL deme-colcine prior to cell cycle analysis and nuclear transfer. The percentage of cat fibroblast cells arrested at the G0/G1 phase in the roscovitine group was similar to that in the control group without any treatment. The percentage of cells arrested at the G2/M phase was significantly higher in the demecolcine group than in the control group. The fusion rate of interspecies couplets was significantly greater in the roscovitine group than in the control group. Most embryos stopped the development at the 2- or 4-cell stage, and none developed into blastocysts. Chemical inhibitor-induced donor cell cycle synchronisation did not overcome developmental arrest in interspecies cloned embryos.

Cav2.1 channels control multivesicular release by relying on their distance from exocytotic Ca2+ sensors at rat cerebellar granule cells

The concomitant release of multiple numbers of synaptic vesicles [multivesicular release (MVR)] in response to a single presynaptic action potential enhances the flexibility of synaptic transmission. However, the molecular mechanisms underlying MVR at a single CNS synapse remain unclear. Here, we show that the Cav2.1 subtype (P/Q-type) of the voltage-gated calcium channel is specifically responsible for the induction of MVR. In the rat cerebellar cortex, paired-pulse activation of granule cell (GC) ascending fibers leads not only to a facilitation of the peak amplitude (PPFamp) but also to a prolongation of the decay time (PPPdecay) of the EPSCs recorded from molecular layer interneurons. PPFamp is elicited by a transient increase in the number of released vesicles. PPPdecay is highly dependent on MVR and is caused by dual mechanisms: (1) a delayed release and (2) an extrasynaptic spillover of the GC transmitter glutamate and subsequent pooling of the glutamate among active synapses. PPPdecay was specifically suppressed by the Cav2.1 channel blocker ω-agatoxin IVA, while PPFamp responded to Cav2.2/Cav2.3 (N-type/R-type) channel blockers. The membrane-permeable slow Ca(2+) chelator EGTA-AM profoundly reduced the decay time constant (τdecay) of the second EPSC; however, it only had a negligible impact on that of the first, thereby eliminating PPPdecay. These results suggest that the distance between presynaptic Cav2.1 channels and exocytotic Ca(2+) sensors is a key determinant of MVR. By transducing presynaptic action potential firings into unique Ca(2+) signals and vesicle release profiles, Cav2.1 channels contribute to the encoding and processing of neural information.

Synthesis and biological evaluation of a selective N- and p/q-type calcium channel agonist

The acute effect of the potent cyclin-dependent kinase (cdk) inhibitor (R)-roscovitine on Ca(2+) channels inspired the development of structural analogues as a potential treatment for motor nerve terminal dysfunction. On the basis of a versatile chlorinated purine scaffold, we have synthesized ca. 20 derivatives and characterized their N-type Ca(2+) channel agonist action. Agents that showed strong agonist effects were also characterized in a kinase panel for their off-target effects. Among several novel compounds with diminished cdk activity, we identified a new lead structure with a 4-fold improved N-type Ca(2+) channel agonist effect and a 22-fold decreased cdk2 activity as compared to (R)-roscovitine. This compound was selective for agonist activity on N- and P/Q-type over L-type calcium channels.

CDK Inhibitors Roscovitine and CR8 Trigger Mcl-1 Down-Regulation and Apoptotic Cell Death in Neuroblastoma Cells

Neuroblastoma (NB), the most frequent extracranial solid tumor of children accounting for nearly 15% of all childhood cancer mortality, displays overexpression of antiapoptotic Bcl-2 and Mcl-1 in aggressive forms of the disease. The clinical phase 2 drug roscovitine (CYC202, seliciclib), a relatively selective inhibitor of cyclin-dependent kinases (CDKs), and CR8, a recently developed and more potent analog, induce concentration-dependent apoptotic cell death of NB cells (average IC(50) values: 24.2 µM and 0.4 µM for roscovitine and CR8, respectively). Both roscovitine and CR8 trigger rapid down-regulation of the short-lived survival factor Mcl-1 in the 9 investigated human NB cell lines. This effect was further analyzed in the human SH-SY5Y NB cell line. Down-regulation of Mcl-1 appears to depend on inhibition of CDKs rather than on interaction of roscovitine and CR8 with their secondary targets. CR8 is an adenosine triphosphate-competitive inhibitor of CDK9, and the structure of a CDK9/cyclin T/CR8 complex is described. Mcl-1 down-regulation occurs both at the mRNA and protein levels. This effect can be accounted for by a reduction in Mcl-1 protein synthesis, under stable Mcl-1 degradation conditions. Mcl-1 down-regulation is accompanied by a transient increase in free Noxa, a proapoptotic factor. Mcl-1 down-regulation occurs independently of the presence or up-regulation of p53 and of the MYCN status. Taken together, these results suggest that the clinical drug roscovitine and its novel analog CR8 induce apoptotic tumor cell death by down-regulating Mcl-1, a key survival factor expressed in all NB cell lines. CDK inhibition may thus constitute a new approach to treat refractory high-risk NB.

Immunodetection of retinoblastoma-related protein and its phosphorylated form in interphase and mitotic alfalfa cells

Plant retinoblastoma-related (RBR) proteins are primarily considered as key regulators of G(1)/S phase transition, with functional roles in a variety of cellular events during plant growth and organ development. Polyclonal antibody against the C-terminal region of the Arabidopsis RBR1 protein also specifically recognizes the alfalfa 115 kDa MsRBR protein, as shown by the antigen competition assay. The MsRBR protein was detected in all cell cycle phases, with a moderate increase in samples representing G(2)/M cells. Antibody against the human phospho-pRb peptide (Ser807/811) cross-reacted with the same 115 kDa MsRBR protein and with the in vitro phosphorylated MsRBR protein C-terminal fragment. Phospho-MsRBR protein was low in G(1) cells. Its amount increased upon entry into the S phase and remained high during the G(2)/M phases. Roscovitine treatment abolished the activity of alfalfa MsCDKA1;1 and MsCDKB2;1, and the phospho-MsRBR protein level was significantly decreased in the treated cells. Colchicine block increased the detected levels of both forms of MsRBR protein. Reduced levels of the MsRBR protein in cells at stationary phase or grown in hormone-free medium can be a sign of the division-dependent presence of plant RBR proteins. Immunolocalization of the phospho-MsRBR protein indicated spots of variable number and size in the labelled interphase nuclei and high signal intensity of nuclear granules in prophase. Structures similar to phospho-MsRBR proteins cannot be recognized in later mitotic phases. Based on the presented western blot and immunolocalization data, the possible involvement of RBR proteins in G(2)/M phase regulation in plant cells is discussed.

Inhibition of CDKS by roscovitine suppressed LPS-induced *NO production through inhibiting NFkappaB activation and BH4 biosynthesis in macrophages

In inflammatory diseases, tissue damage is critically associated with nitric oxide ((*)NO) and cytokines, which are overproduced in response to cellular release of endotoxins. Here we investigated the inhibitory effect of roscovitine, a selective inhibitor of cyclin-dependent kinases (CDKs) on (*)NO production in mouse macrophages. In RAW264.7 cells, we found that roscovitine abolished the production of (*)NO induced by lipopolysaccharide (LPS). Moreover, roscovitine significantly inhibited LPS-induced inducible nitric oxide synthase (iNOS) mRNA and protein expression. Our data also showed that roscovitine attenuated LPS-induced phosphorylation of IkappaB kinase beta (IKKbeta), IkappaB, and p65 but enhanced the phosphorylation of ERK, p38, and c-Jun NH(2)-terminal kinase (JNK). In addition, roscovitine dose dependently inhibited LPS-induced expression of cyclooxygenase-2 (COX)-2, IL-1beta, and IL-6 but not tumor necrosis factor (TNF)-alpha. Tetrahydrobiopterin (BH(4)), an essential cofactor for iNOS, is easily oxidized to 7,8-dihydrobiopterin (BH(2)). Roscovitine significantly inhibited LPS-induced BH(4) biosynthesis and decreased BH(4)-to-BH(2) ratio. Furthermore, roscovitine greatly reduced the upregulation of GTP cyclohydrolase-1 (GCH-1), the rate-limiting enzyme for BH(4) biosynthesis. Using other CDK inhibitors, we found that CDK1, CDK5, and CDK7, but not CDK2, significantly inhibited LPS-induced (*)NO production in macrophages. Similarly, in isolated peritoneal macrophages, roscovitine strongly inhibited (*)NO production, iNOS, and COX-2 upregulation, activation of NFkappaB, and induction of GCH-1 by LPS. Together, our data indicate that roscovitine abolishes LPS-induced (*)NO production in macrophages by suppressing nuclear factor-kappaB activation and BH(4) biosynthesis, which might be mediated by CDK1, CDK5, and CDK7. Our results also suggest that roscovitine may inhibit inflammation and that CDKs may play important roles in the mechanisms by which roscovitine attenuates inflammation.

Roscovitine reduces neuronal loss, glial activation, and neurologic deficits after brain trauma

Traumatic brain injury (TBI) causes both direct and delayed tissue damage. The latter is associated with secondary biochemical changes such as cell cycle activation, which leads to neuronal death, inflammation, and glial scarring. Flavopiridol--a cyclin-dependent kinase (CDK) inhibitor that is neither specific nor selective--is neuroprotective. To examine the role of more specific CDK inhibitors as potential neuroprotective agents, we studied the effects of roscovitine in TBI. Central administration of roscovitine 30 mins after injury resulted in significantly decreased lesion volume, as well as improved motor and cognitive recovery. Roscovitine attenuated neuronal death and inhibited activation of cell cycle pathways in neurons after TBI, as indicated by attenuated cyclin G1 accumulation and phosphorylation of retinoblastoma protein. Treatment also decreased microglial activation after TBI, as reflected by reductions in ED1, galectin-3, p22(PHOX), and Iba-1 levels, and attenuated astrogliosis, as shown by decreased accumulation of glial fibrillary acidic protein. In primary cortical microglia and neuronal cultures, roscovitine and other selective CDK inhibitors attenuated neuronal cell death, as well as decreasing microglial activation and microglial-dependent neurotoxicity. These data support a multifactorial neuroprotective effect of cell cycle inhibition after TBI--likely related to inhibition of neuronal apoptosis, microglial-induced inflammation, and gliosis--and suggest that multiple CDKs are potentially involved in this process.

Autophagy: a novel mechanism of synergistic cytotoxicity between doxorubicin and roscovitine in a sarcoma model

Doxorubicin is a genotoxic chemotherapy agent used in treatment of a wide variety of cancers. Significant clinical side effects, including cardiac toxicity and myelosuppression, severely limit the therapeutic index of this commonly used agent and methods which improve doxorubicin efficacy could benefit many patients. Because doxorubicin cytotoxicity is cell cycle specific, the cell cycle is a rational target to enhance its efficacy. We examined the direct, cyclin-dependent kinase inhibitor roscovitine as a means of enhancing doxorubicin cytotoxicity. This study showed synergistic cytotoxicity between doxorubicin and roscovitine in three sarcoma cell lines: SW-982 (synovial sarcoma), U2OS-LC3-GFP (osteosarcoma), and SK-LMS-1 (uterine leiomyosarcoma), but not the fibroblast cell line WI38. The combined treatment of doxorubicin and roscovitine was associated with a prolonged G(2)-M cell cycle arrest in the three sarcoma cell lines. Using three different methods for detecting apoptosis, our results revealed that apoptotic cell death did not account for the synergistic cytotoxicity between doxorubicin and roscovitine. However, morphologic changes observed by light microscopy and increased cytoplasmic LC3-GFP puncta in U20S-LC3-GFP cells after the combined treatment suggested the induction of autophagy. Induction of autophagy was also shown in SW-982 and SK-LMS-1 cells treated with both doxorubicin and roscovitine by acridine orange staining. These results suggest a novel role of autophagy in the enhanced cytotoxicity by cell cycle inhibition after genotoxic injury in tumor cells. Further investigation of this enhanced cytotoxicity as a treatment strategy for sarcomas is warranted.

Restoration of renal function in zebrafish models of ciliopathies

The ciliopathies are a class of rare human genetic disease whose aetioligies lie in defective primary cilia. Typical ciliopathies include Bardet-Biedl syndrome (BBS), nephronophthisis (NPHP), Jeune, Joubert, oro-facial-digital (OFD1) and Meckel (MKS) syndromes. All ciliopathies have the common denominator of renal disease, often including tubular cysts. In this study, we have modelled a range of ciliopathies in zebrafish and shown in all cases that knocking down these genes causes cystic lesions in the kidney. We have identified two drugs, rapamycin and roscovitine, which ameliorate the renal phenotype, both morphologically and functionally. This is the first study in which zebrafish has been used to identify potential therapeutic modalities for ciliopathic renal disease, and the results pave the way for further investigations in mammalian models.

Cyclosporin A enhances colchicine-induced apoptosis in rat cerebellar granule neurons

1. Cyclosporin A (CsA, 1-50 microM), an immunosuppressive drug with known neurotoxic effects, did not decrease the viability of primary cultures of rat cerebellar granule neurons (CGN) or induce apoptotic features. However, CsA specifically enhanced the cytotoxicity and apoptosis induced by colchicine (1 microM). 2. Flavopiridol, an inhibitor of cyclin-dependent kinases (CDKs), prevented the neurotoxic effects of colchicine plus CsA. At 0.1-5 microM, it also showed antiapoptotic effects, as revealed by propidium iodide staining, flow cytometry and counting of cell nuclei. 3. Roscovitine (25-50 microM), a selective cdk1, 2 and 5 inhibitor, showed an antiapoptotic effect against colchicine- and colchicine plus CsA-induced apoptosis. 4. CsA increased the expression of cdk5 and cdk5/p25 mediated by colchicine, a CDK involved in neuronal apoptosis. After treatment of CGN with colchicine plus CsA, the changes in the p25/p35 ratio pointed to cdk5 activation. 5. Immunohistochemical results showed a nuclear localization of cdk5 after neurotoxic treatment, which was prevented by cdk inhibitors. Thus, we propose a new mechanism of modulation of CsA neurotoxicity mediated by cdk5.

In vivo release of mitotic silencing of ribosomal gene transcription does not give rise to precursor ribosomal RNA processing

Nuclear RNA transcription is repressed when eukaryotic cells enter mitosis. Here, we found that the derepression of ribosomal gene (rDNA) transcription that normally takes place in telophase may be induced in prometaphase, metaphase, and anaphase mitotic HeLa cells, and therefore appears not to be dependent on completion of mitosis. We demonstrate for the first time that in vivo inhibition of the cdc2- cyclin B kinase activity is sufficient to give rise to okadaic acid-sensitive dephosphorylation of the mitotically phosphorylated forms of components of the rDNA transcription machinery, and consequently to restore rDNA transcription in mitotic cells. These results, showing that during mitosis the rDNA transcription machinery is maintained repressed by the cdc2-cyclin B kinase activity, provide an in vivo demonstration of the cell cycle-dependent regulation of rDNA transcription. Interestingly in mitotic cells, the newly synthesized 47S precursor ribosomal RNA (pre-rRNA) is not processed into the mature rRNAs, indicating that rDNA transcription and pre-rRNA processing may be uncoupled. Moreover this suggests that inhibition of the cdc2- cyclin B kinase is not sufficient to activate the 47S pre-rRNA processing machinery and/or to induce its relocalization at the level of newly synthesized 47S pre-rRNA. This in vivo approach provides new possibilities to investigate the correlation between pre-rRNA synthesis and pre-rRNA processing when the nucleolus reforms.