PDE11A negatively regulates lithium responsivity

Molecular Psychiatry (2017) 22, 1714–1724 OPEN www.nature.com/mp ORIGINAL ARTICLE PDE11A negatively regulates lithium responsivity G Pathak1, MJ Agostino2, K Bishara1, WR Capell1, JL Fisher1, S Hegde1, BA Ibrahim1, K Pilarzyk1, C Sabin1, T Tuczkewycz3,4, S Wilson1 and MP Kelly1 Lithium responsivity in patients with bipolar disorder has been genetically associated with Phosphodiesterase 11A (PDE11A), and lithium decreases PDE11A mRNA in induced pluripotent stem cell-derived hippocampal neurons originating from lithium-responsive patients. PDE11 is an enzyme uniquely enriched in the hippocampus that breaks down cyclic AMP and cyclic GMP. Here we determined whether decreasing PDE11A expression is sufficient to increase lithium responsivity in mice. In dorsal hippocampus and ventral hippocampus (VHIPP), lithium-responsive C57BL/6J and 129S6/SvEvTac mice show decreased PDE11A4 protein expression relative to lithium-unresponsive BALB/cJ mice. In VHIPP, C57BL/6J mice also show differences in PDE11A4 compartmentalization relative to BALB/cJ mice. In contrast, neither PDE2A nor PDE10A expression differ among the strains. The compartment-specific differences in PDE11A4 protein expression are explained by a coding single-nucleotide polymorphism (SNP) at amino acid 499, which falls within the GAF-B homodimerization domain. Relative to the BALB/cJ 499T, the C57BL/6J 499A decreases PDE11A4 homodimerization, which removes PDE11A4 from the membrane. Consistent with the observation that lower PDE11A4 expression correlates with better lithium responsiveness, we found that Pde11a knockout mice (KO) given 0.4% lithium chow for 3+ weeks exhibit greater lithium responsivity relative to wild-type (WT) littermates in tail suspension, an antidepressant-predictive assay, and amphetamine hyperlocomotion, an anti-manic predictive assay. Reduced PDE11A4 expression may represent a lithium-sensitive pathophysiology, because both C57BL/6J and Pde11a KO mice show increased expression of the pro-inflammatory cytokine interleukin-6 (IL-6) relative to BALB/cJ and PDE11A WT mice, respectively. Our finding that PDE11A4 negatively regulates lithium responsivity in mice suggests that the PDE11A SNPs identified in patients may be functionally relevant. Molecular Psychiatry (2017) 22, 1714–1724; doi:10.1038/mp.2016.155; published online 20 September 2016 INTRODUCTION Lithium is argued to be the best treatment option for patients with bipolar disorder, but it has a narrow therapeutic window due to significant side effect liability.1 If we could selectively augment the beneficial mood stabilizing effects of lithium in the brain without increasing its harmful peripheral side effects, we might be able to improve the safety margin of lithium treatment for patients with bipolar disorder because mood stabilization could be achieved with systemically lower doses. One way to achieve this selective augmentation of lithium’s positive effects is to target a molecule that is selectively expressed in the brain. Phosphodiesterase 11A (PDE11A) hydrolyzes cyclic AMP (cAMP) and cyclic GMP (cGMP) equally well2,3 and is the only PDE to be preferentially expressed in the hippocampus.4–6 We have shown in rodents that PDE11A4, the longest PDE11A isoform, is almost exclusively expressed in CA1 and subiculum of the ventral hippocampus (VHIPP), with minimal expression in the dorsal HIPP (DHIPP)4,6 and little to no protein expression outside of the brain.5 Genetic findings in humans suggest a role for PDE11A in brain function7–12 (but see Laje et al.,13 Perlis et al.14). For example, PDE11A single-nucleotide polymorphisms (SNPs) have been associated with major depression and antidepressant response7–9 (but see Laje et al.,13 Perlis et al.14). Of particular interest to the present study, PDE11A SNPs have been associated with lithium responsiveness in patients with bipolar disorder,10,11 a PDE11A inactivating mutation has been associated with increased suicide risk12—a symptom lithium uniquely reduces in patients with bipolar disorder,15 and lithium decreases PDE11A mRNA expression in induced Pluripotent Stem Cell (iPSC)-derived hippocampal neurons originating from lithium-responsive patients but not from lithium-unresponsive patients.16 A relationship between lithium and cyclic nucleotide signaling is well precedented. Lithium is known to modulate cyclic nucleotide signaling (cf., Gould et al.17), and disturbances in cyclic nucleotide signaling have repeatedly been observed in patients with bipolar disorder (for example, refs 18–26). Interestingly, the alterations in cyclic nucleotide signaling identified in patients with bipolar disorder can be subcellular compartment specific,18,23,25 as can be the effects of lithium on cyclic nucleotide signaling.27–29 Therefore, we determined whether PDE11A expression and/or compartmentalization differ between mouse strains that respond well versus poorly to lithium. Furthermore, we determined whether differences in PDE11A compartmentalization are due to a non-synonymous coding SNP that exists between mouse strains at amino acid 499, which is positioned within the GAF-B homodimerization domain. We also established whether decreasing PDE11A expression is sufficient to strengthen the antidepressant-like effects of lithium in the tail suspension test (TST) and the anti-manic-like effects of lithium in amphetaminestimulated hyperactivity by testing Pde11a wild-type (WT) and knockout (KO) mice. Finally, we determined whether PDE11A controls protein expression of the pro-inflammatory cytokine 1 Department of Pharmacology, Physiology & Neuroscience, University of South Carolina School of Medicine, Columbia, SC, USA; 2Pfizer, Andover, MA, USA and 3Pfizer, Groton, CT, USA. Correspondence: Dr MP Kelly, Department of Pharmacology, Physiology & Neuroscience, University of South Carolina School of Medicine, 6439 Garners Ferry Road VA Bldg 1, 3rd Floor, D-12, Columbia, SC 29209, USA. E-mail: 4 Current address: Biogen, Boston, MA, USA. Received 11 December 2015; revised 13 July 2016; accepted 18 July 2016; published online 20 September 2016 PDE11A negatively regulates lithium responsivity G Pathak et al interleukin-6 (IL-6), a potential mood disorder biomarker,30–37 to clarify whether PDE11A holds promise as a possible target for adjuvant treatment or simply as a patient selection marker. MATERIALS AND METHODS Subjects C57BL/6J (The Jackson Laboratories (JAX); Bar Harbor, ME, USA), BALB/cJ (JAX) and 129S6/SvEvTac mice (Taconic, Hudson, NY, USA) were ordered in at 10–12 weeks or bred onsite. All C57BL/6J, BALB/cJ and 129S6/SvEvTac mice were group housed and habituated to the colony at least 1 week prior to killing. mRNA analyses and protein analyses of the whole hippocampus using these strains were conducted on cohorts of all males; however, protein analyses on DHIPP vs VHIPP were conducted on mixed cohorts of males and females (cohort used in Figures 1d–g and Supplementary Figure S3 = 50% female; cohort used in Figur (...truncated)