UWA-101 Exacerbates the Severity of Psychosis-like Behaviour at High Doses
In a previous series of experiments, we demonstrated that UWA-101 did not induce behaviours attributable to psychoactivity when administered as monotherapy to normal, non-parkinsonian animals [13]. However, in the current study, adding UWA-101 to L-DOPA resulted in an exacerbation of L-DOPA-induced psychosis-like behaviours at the higher doses examined.Figure 4. Psychosis-like behaviours. A. UWA-101 (6, 10 mg/kg) exacerbated the severity of psychosis-like behaviours. The addition of UWA-101 6 mg/kg to L-DOPA resulted in significantly more severe psychosis-like behaviours when compared to L-DOPA/ vehicle (at time 120 min post drug administration, P,0.001). L-DOPA/ UWA-101 6 mg/kg also led to significantly more severe psychosis-like behaviours than the L-DOPA/ UWA-101 1 mg/kg (120 min and 180 min post drug administration, P,0.01 and P,0.05, respectively) and the L-DOPA/ UWA-101 3 mg/kg (60 min and 120 min post drug administration, P,0.05 and P,0.001, respectively) treatments. Psychosis-like behaviours were also significantly more severe when L-DOPA/ UWA-101 10 mg/kg was compared to L-DOPA/ vehicle (60 and 120 min post drug administration, both P,0.05), L-DOPA/ UWA-101 1 mg/ kg (60 min post drug administration, P,0.01) and L-DOPA/ UWA-101 3 mg/kg (60 min and 120 min post drug administration, P,0.001 and P,0.01, respectively) treatments. Each time point represents the cumulated psychosis-like behaviours scores for every 5 min observation period during the preceding 60 min. The maximal possible score (most severe disability) was 24. On the y-axis, mild = 6, moderate = 12, marked = 18, severe = 24. The crosses on the graph represent time points for which there is statistical significance. B. UWA-101, in combination with L-DOPA, did not alter duration of ON-time with psychosis-like behaviours. Following administration of L-DOPA/ vehicle, the mean duration of ON-time with psychosis-like behaviours was 188.0624.8 min. This was not significantly modified when UWA-101 (1, 3, 6, 10 mg/kg) was added to L-DOPA (all P.0.05). *: P,0.05 when compared to vehicle; ***: P,0.001 when compared to vehicle; #: P,0.05 when compared to UWA-101 1 mg/kg; ##: P,0.01 when compared to UWA-101 1 mg/kg; {: P,0.05 when compared to UWA-101 3 mg/kg; {{: P,0.01 when compared to UWA-101 3 mg/kg; {{{: P,0.001 when compared to UWA-101 3 mg/kg. Data are expressed as the median (B) and as the mean 6 SEM (B). We hypothesise that these effects to exacerbate psychosis emerge from inhibition of SERT and indirect stimulation of serotonergic type 2A (5-HT2A) receptors. Thus, as described above, in the presence of L-DOPA, inhibition of SERT by UWA101 would lead to increased dopamine levels surrounding Table 1. Order of treatments.
serotonergic synapses. Dopamine binds to 5-HT2A receptors, at which it acts as a partial agonist [34]. 5-HT2A receptors are believed to be important in the genesis of psychotic symptoms in PD and other disorders. Indeed, activating 5-HT2A receptors is thought to be an important mechanism of action of hallucinogens [35] and, conversely, antagonising 5-HT2A receptors is believed to underlie the action of atypical antipsychotics such as clozapine [36,37]. Moreover, 5-HT2A receptors are increased in the temporal cortex of PD patients with visual hallucinations [38,39]. Thus, UWA-101, by blocking both SERT and DAT would elevate dopamine levels and thereby increasing stimulation, by dopamine, of 5-HT2A receptors.
Concluding Remarks
Since UWA-101 is the first dual SERT/ DAT inhibitor to be tested in PD models, it is hard to generalise but, we propose that, in order to employ monoamine re-uptake inhibitors, in combination with L-DOPA, to increase duration of ON-time without adversely affecting dyskinesia, it might be necessary to antagonise both the SERT and DAT. However, it will be necessary to define optimal therapeutic windows with this class of drugs because atTable 1 shows the randomised Latin square design employed in the current study. Such a design allows all subjects to receive all treatments, once, in a different, randomly assigned, order, thereby minimising the risk of carryover effect. higher doses it appears that dual SERT/ DAT inhibition can exacerbate the severity of psychosis-like behaviours. Moreover, whether the anti-parkinsonian efficacy and the lack of deleterious effect on dyskinesia severity, of UWA-101 as adjunct therapy to LDOPA will be maintained after chronic administration remains unknown.
Abstract
Tip60 (KAT5) is a histone acetyltransferase (HAT enzyme) involved in multiple cellular processes including transcriptional regulation, DNA damage repair and cell signalling. In prostate cancer, aggressive cases over-express Tip60 which functions as an androgen receptor co-activator via direct acetylation of lysine residues within the KLKK motif of the receptor hinge region. The purpose of this study was to identify and characterise a Tip60 acetylase inhibitor. High-throughput screening revealed an isothiazole that inhibited both Tip60 and p300 HAT activity. This substance (initially identified as 4-methyl-5bromoisothiazole) and other isothiazoles were synthesised and assayed against Tip60. Although an authentic sample of 4methyl-5-bromoisothiazole was inactive against Tip60, in an in vitro HAT assay, 1,2-bis(isothiazol-5-yl)disulfane (NU9056) was identified as a relatively potent inhibitor (IC50 2 mM). Cellular activity was confirmed by analysis of acetylation of histone and non-histone proteins in a prostate cancer cell line model. NU9056 treatment inhibited cellular proliferation in a panel of prostate cancer cell lines (50% growth inhibition, 8?7 mM) and induced apoptosis via activation of caspase 3 and caspase 9 in a concentration- and time-dependent manner. Also, decreased androgen receptor, prostate specific antigen, p53 and p21 protein levels were demonstrated in response to treatment with NU9056. Furthermore, pre-treatment with NU9056 inhibited both ATM phosphorylation and Tip60 stabilization in response to ionising radiation. Based on the activity of NU9056 and the specificity of the compound towards Tip60 relative to other HAT enzymes, these chemical biology studies have identified Tip60 as a potential therapeutic target for the treatment of prostate cancer.
