Deletion of phosphodiesterase 4D in mice shortens α2-adrenoceptor–mediated anesthesia, a behavioral correlate of emesis

Abstract

IntroductionCyclic nucleotides cAMP and cGMP are degraded by at least 11 families of phosphodiesterases (PDEs 1-11) classified according to their gene sequence, substrate specificity, biochemical regulation, and sensitivity to inhibitors (1, 2). The cAMP-specific PDE4 has attracted considerable attention for the treatment of airway inflammatory diseases, since its inhibition results in attenuated inflammatory responses (1,3,4). However, the therapeutic potential of PDE4 inhibitors has been limited by the side effects of nausea and emesis, observed both in humans and in various animal species following the administration of structurally diverse compounds (5-9). A major challenge in the development of new generations of PDE4 inhibitors is the improvement of the therapeutic index of this class of compounds.PDE4 enzymes use a common binuclear ion center as the core catalytic machinery (10). The reversible binding of the cation cofactors (e.g., Mg 2+ ) results in the presence of two coexisting conformers that bind inhibitors differently: the holoenzyme (enzyme bound with Mg 2+ ) and the apoenzyme (free enzyme) (11,12). In the past, it was observed that the potency of some inhibitors (e.g., rolipram) on PDE activity deviated from their affinity at the high-affinity rolipram binding site (HARBS); this led to the proposal that inhibitors with a reduced potency on the HARBS may have an improved therapeutic index over that of firstgeneration compounds (13-15). It has now been clarified that the HARBS corresponds to the holoenzyme conformer responsible for PDE4 catalysis (11,12).The PDE4 family is composed of four subtypes (PDE4A-D) and multiple splice variants (16). If it were possible to identify the subtype(s) responsible for the beneficial and the side effects associated with PDE4 inhibition, then subtype-selective inhibitors devoid of the tendency to induce nausea and vomiting could be developed. The mechanism of the emetic response associated with PDE4 inhibitors is thought to be a consequence of the inhibition of PDE4 in nontarget tissues (9, 13). It is believed that PDE4 inhibitors produce a pharmacologi- A combination of pharmacological and genetic approaches was used to determine the role of type 4 cAMP-specific cyclic nucleotide phosphodiesterase 4 (PDE4) in reversing α 2 -adrenoceptor-mediated anesthesia, a behavioral correlate of emesis in non-vomiting species. Among the family-specific PDE inhibitors, PDE4 inhibitors reduced the duration of xylazine/ketamine-induced anesthesia in mice, with no effect on pentobarbital-induced anesthesia. The rank order of the PDE4 inhibitors tested was 6-(4- -2450). The specific roles of PDE4B and PDE4D in this model were studied using mice deficient in either subtype. PDE4D-deficient mice, but not PDE4B-deficient mice, had a shorter sleeping time than their wild-type littermates under xylazine/ketamine-induced anesthesia, but not under that induced with pentobarbital. Concomitantly, rolipram-sensitive PDE activity in the brain stem was decreased only in PDE4D-deficient mice c...

Action of a Novel PDE4 inhibitor ZL-n-91 on lipopolysaccharide-induced acute lung injury

“…If it were possible to identify the subtype (s) responsible for the beneficial and the side effects associated with PDE4 inhibition, then subtype-selective inhibitors devoid of the tendency to induce nausea and vomiting could be developed. The mechanism of the emetic response associated with PDE4 inhibitors is thought to be a consequence of the inhibition of PDE4D subtype [9,10], But which PDE4D subtype was involved in the nausea action was unclear. Recently advance suggested that PDE4D modify the stroke risk in the Swedish population [3].…”

“…Experiments were conducted following procedures previously described [9,10]. Briefly, mice were anesthetized with the combination of xylazine (10 mg/kg, sigma, USA) and ketamine (80 mg/kg, Zhejiang Xianju Pharmaceutical Co. LTD, China) administered in a single intraperitoneal injection.…”

Behavioral and neurochemical characterization of mice deficient in the phosphodiesterase-4B (PDE4B) enzyme

“…Rolipram [(±)-4-(3-cyclopentyloxy-4-methoxyphenyl)-2-pyrrolidone], one of the most widely studied PDE inhibitors (Schneider 1984;Wachtel 1983a,b) inhibits all PDE4 subtypes (MacKenzie and Houslay 2000; Robichaud et al 2002). However, the recent availability of genetically modified mice that lack either the PDE4B or PDE4D genes has made studies exploring the role of the PDE4 subtypes possible (Jin et al 1999(Jin et al , 2005Jin and Conti 2002).…”

Antipsychotic profile of rolipram: efficacy in rats and reduced sensitivity in mice deficient in the phosphodiesterase-4B (PDE4B) enzyme

“…Rolipram is well absorbed, shows good bioavailability, and after oral or subcutaneous administration in rat, the serum half-life of rolipram is about 1 h Kuhne 1988, 1993). Rolipram inhibits all PDE4 subtypes (MacKenzie and Houslay 2000; Robichaud et al 2002) and has no reported activity at other PDEs, enzymes, or neurotransmitter receptors. Unfortunately, one of the major limitations within the PDE4 field is the lack of commercially available subtype-selective inhibitors.…”