Phosphodiesterase 4 inhibition reduces lung fibrosis following targeted type II alveolar epithelial cell injury

Fibrosis of the lung constitutes a major clinical challenge and novel therapies are required to alleviate the associated morbidity and mortality. Investigating the antifibrotic efficacy of drugs that are already in clinical practice offers an efficient strategy to identify new therapies. The phosphodiesterase 4 (PDE4) inhibitors, approved for the treatment of chronic obstructive pulmonary disease, harbor therapeutic potential for pulmonary fibrosis by augmenting the activity of endogenous antifibrotic mediators that signal through cyclic AMP. In this study, we tested the efficacy of several PDE4 inhibitors including a novel compound (Compound 1) in a murine model of lung fibrosis that results from a targeted type II alveolar epithelial cell injury. We also compared the antifibrotic activity of PDE4 inhibition to the two therapies that are FDA‐approved for idiopathic pulmonary fibrosis (pirfenidone and nintedanib). We found that both preventative (day 0–21) and therapeutic (day 11–21) dosing regimens of the PDE4 inhibitors significantly ameliorated the weight loss and lung collagen accumulation that are the sequelae of targeted epithelial cell damage. In a therapeutic protocol, the reduction in lung fibrosis with PDE4 inhibitor administration was equivalent to pirfenidone and nintedanib. Treatment with this class of drugs also resulted in a decrease in plasma surfactant protein D concentration, a reduction in the plasma levels of several chemokines implicated in lung fibrosis, and an in vitro inhibition of fibroblast profibrotic gene expression. These results motivate further investigation of PDE4 inhibition as a treatment for patients with fibrotic lung disease.We demonstrate that prophylactic and therapeutic inhibition of phosphodiesterase 4 with several different antagonists reduces lung fibrosis induced by a targeted injury to the type II alveolar epithelium. In conjunction with the reduction in lung collagen content, phosphodiesterase inhibition also reduced serum surfactant protein C levels and the expression of profibrotic genes by lung fibroblasts.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/144679/1/phy213753.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/144679/2/phy213753_am.pd

Characterization of binding and inhibitory properties of TAK-063, a novel phosphodiesterase 10A inhibitor.

Phosphodiesterase 10A (PDE10A) inhibition is a novel and promising approach for the treatment of central nervous system disorders such as schizophrenia and Huntington's disease. A novel PDE10A inhibitor, TAK-063 [1-[2-fluoro-4-(1H-pyrazol-1-yl)phenyl]-5-methoxy-3-(1-phenyl-1H-pyrazol-5-yl)-pyridazin-4(1H)-one] has shown high inhibitory activity and selectivity for human recombinant PDE10A2 in vitro; the half-maximal inhibitory concentration was 0.30 nM, and selectivity over other phosphodiesterases (PDEs) was more than 15000-fold. TAK-063 at 10 µM did not show more than 50% inhibition or stimulation of 91 enzymes or receptors except for PDEs. In vitro autoradiography (ARG) studies using rat brain sections revealed that [3H]TAK-063 selectively accumulated in the caudate putamen (CPu), nucleus accumbens (NAc), globus pallidus, substantia nigra, and striatonigral projection, where PDE10A is highly expressed. This [3H]TAK-063 accumulation was almost entirely blocked by an excess amount of MP-10, a PDE10A selective inhibitor, and the accumulation was not observed in brain slices of Pde10a-knockout mice. In rat brain sections, [3H]TAK-063 bound to a single high-affinity site with mean ± SEM dissociation constants of 7.2 ± 1.2 and 2.6 ± 0.5 nM for the CPu and NAc shell, respectively. Orally administered [14C]TAK-063 selectively accumulated in PDE10A expressing brain regions in an in vivo ARG study in rats. Striatal PDE10A occupancy by TAK-063 in vivo was measured using T-773 as a tracer and a dose of 0.88 mg/kg (p.o.) was calculated to produce 50% occupancy in rats. Translational studies with TAK-063 and other PDE10A inhibitors such as those presented here will help us better understand the pharmacological profile of this class of potential central nervous system drugs

Percent inhibition of enzymes by TAK-063 at 10 μM.

<p>EGF, epidermal growth factor; HMG CoA, 3-hydroxy-3-methyl-glutaryl coenzyme A. Negative value of percent inhibition indicates activation of enzyme activity.</p><p>Percent inhibition of enzymes by TAK-063 at 10 μM.</p

<i>In vitro</i> autoradiography (ARG) using [³H]TAK-063 in mouse brain sections.

<p>[³H]TAK-063 selectively accumulated in the caudate putamen (CPu; black arrow) and nucleus accumbens (NAc; white arrow) of wild-type (WT) mouse brain sections (A). The selective accumulation of [³H]TAK-063 in these areas did not occur in <i>Pde10a</i>-KO mouse brain sections (B). Radioactivity levels in the CPu of brain sections in the presence and absence of an excess amount of MP-10 are represented as a percent of total binding of WT mice (C). Data are represented as mean ± SEM.</p

Concentration of T-773 in the rat brain and displacement by TAK-063.

<p>The data (ng/g tissue) are represented as mean (n = 2 at 0.3 mg/kg) or mean ± SEM (n = 3).</p><p>Concentration of T-773 in the rat brain and displacement by TAK-063.</p

<i>In vitro</i> autoradiography (ARG) using [³H]TAK-063 in sagittal rat brain sections.

<p>The chemical structure of [³H]TAK-063 (A). Sections adjacent to those used for <i>in vitro</i> ARG of [³H]TAK-063, were stained with hematoxylin and eosin (B). The autoradiogram shows the high accumulation of [³H]TAK-063 in the caudate putamen (CPu; white arrow), nucleus accumbens (NAc; black arrow), globus pallidus (GP; white arrow head), substantia nigra (SN; black arrow head), and striatonigral projection (gray arrow; C). <i>In vitro</i> ARGs in the presence of an excess amount of MP-10 (D) or TAK-063 (E) were performed with adjacent sections. Radioactivity levels in several brain regions were represented as photostimulated luminescence (PSL) values in the presence or absence of an excess amount of MP-10 or TAK-063 (F). Statistical analyses were performed using Dunnett's test (*<i>P</i> ≤ 0.05, **<i>P</i> ≤ 0.01 vs total binding, n = 3). Fcx, frontal cortex; Thal, thalamus; Bs, brainstem; Hipp, hippocampus; Cb, cerebellum.</p

<i>In vivo</i> ARG of [¹⁴C]TAK-063 in rats.

<p>The chemical structure of [¹⁴C]TAK-063 (A). The asterisk denotes the labeled position. Autoradiograms of head sections were obtained from male rats 6 h after single oral administration of [¹⁴C]TAK-063. The autoradiograms of 40 μm sagittal sections between 2.1 to 2.4 mm lateral to midline were taken (B). The locations for each coronal section relative to the bregma were 1.7 to 1.2 mm (C), 0.48 to −0.26 mm (D), −0.4 to −0.8 mm (E), −2.8 to −3.1 mm (F), −6.0 to −6.3 mm (G), and −12.7 to −12.8 mm (H). Acc, nucleus accumbens; Cb, cerebellum; Cpu, caudate putamen; Ctx, cortex; Fcx, frontal cortex; GP, globus pallidus; Hipp, hippocampus; MO, medulla oblongata; OT, olfactory tubercle; SN, substantia nigra; Thal, thalamus; VP, ventral pallidum.</p