IBMX

IBMX is a broad-spectrum phosphodiesterase (PDE) inhibitor, with IC50 of 6.5±1.2, 26.3±3.9 and 31.7±5.3 μM for PDE3, PDE4 and PDE5, respectively.

In Vitro:At 100 μM, KMUP-1 (a xanthine derivative) and IBMX are the most effective at inducing tracheal relaxation; the magnitude of the relaxation responses induced by KMUP-1 and IBMX are not significantly different[1]. IBMX (100 μM) activates renal outer medullary K+ (ROMK) channels (n=6, P<0.05) and prevents further channel activation by ANG II (n=6, P=NS) or cGMP. Of note is that pretreatment of cortical collecting duct (CCDs) isolated from high-K+ (HK)-fed rats with IBMX (100 μM) for 20 min leads to a significant increase in tubular cAMP content to 1.43±0.35 pg/mm tubule length (n=14) compare with that measured in vehicle-treated controls (0.61±0.13 pg/mm tubule length, n=12, P<0.05)[2].

In Vivo:IBMX, a non-selective PDE inhibitor significantly decreases the liver glycogen storage (mg/g, IBMX 22±1.5 P<0.001). IBMX potentiates insulin release and in hepatocytes and adipocytes, they increase glycogenolysis and lipolysis. In comparison with the control group, IBMX and mc5 significantly increase plasma glucose (blood glucose, mg/dl, control=141±3, IBMX=210±17 P<0.001 and mc5=191±13 P<0.01) while other test compounds (mc1, mc6, MCPIP and milrinone) do not produce significant effect (control=141±3, mc1 160±7, mc6 175±9, MCPIP 179±8 and milrinone 116±2 P>0.05) also mc2 does not change plasma glucose (control=141±3 and mc2=145±5). IBMX has the highest efficacy on increasing plasma glucose[3]. Treatments with IBMX and Apocynin significantly decrease cold-induced elevation of right ventricular (RV) systolic pressure (23.5±1.8 and 24.2±0.6 mmHg, respectively) although they do not decrease RV pressure to the warm control levels. IBMX or Apocynin significantly reduces medial layer thickness (19.0±0.9, and 16.9±0.8 μm, respectively) and increases lumen diameter (62.7±4.2, and 59.5±4.3 μm, respectively) of small PAs in cold-exposed rats[4].

References:
[1]. Wu BN, et al. KMUP-1, a xanthine derivative, induces relaxation of guinea-pig isolated trachea: the role of the epithelium, cyclic nucleotides and K+ channels. Br J Pharmacol. 2004 Aug;142(7):1105-14. [2]. Wei Y, et al. Angiotensin II type 2 receptor regulates ROMK-like K+ channel activity in the renal cortical collecting duct during high dietary K+ adaptation. Am J Physiol Renal Physiol. 2014 Oct 1;307(7):F833-43. [3]. Hosseini A, et al. Differential metabolic effects of novel cilostamide analogs, methyl carbostiryl derivatives, on mouse and hyperglycemic rat. Iran J Basic Med Sci. 2012 Jul;15(4):916-25. [4]. Crosswhite P, et al. Inhibition of phosphodiesterase-1 attenuates cold-induced pulmonary hypertension. Hypertension. 2013 Mar;61(3):585-92.

Corrigendum: Unfractionated and Low-Molecular-Weight Heparin and the Phosphodiesterase Inhibitors, IBMX and Cilostazol, Block Ex Vivo Equid Herpesvirus Type-1-Induced Platelet Activation.[Pubmed:28194402]

Front Vet Sci. 2017 Feb 10;4:10.

[This corrects the article on p. 99 in vol. 3, PMID: 27909693.].

Unfractionated and Low-Molecular-Weight Heparin and the Phosphodiesterase Inhibitors, IBMX and Cilostazol, Block Ex Vivo Equid Herpesvirus Type-1-Induced Platelet Activation.[Pubmed:27909693]

Front Vet Sci. 2016 Nov 17;3:99.

Equid herpes virus type-1 (EHV-1) is a major pathogen of horses, causing abortion storms and outbreaks of herpes virus myeloencephalopathy. These clinical syndromes are partly attributed to ischemic injury from thrombosis in placental and spinal vessels. The mechanism of thrombosis in affected horses is unknown. We have previously shown that EHV-1 activates platelets through virus-associated tissue factor-initiated thrombin generation. Activated platelets participate in thrombus formation by providing a surface to localize coagulation factor complexes that amplify and propagate thrombin generation. We hypothesized that coagulation inhibitors that suppress thrombin generation (heparins) or platelet inhibitors that impede post-receptor thrombin signaling [phosphodiesterase (PDE) antagonists] would inhibit EHV-1-induced platelet activation ex vivo. We exposed platelet-rich plasma (PRP) collected from healthy horses to the RacL11 abortigenic and Ab4 neuropathogenic strains of EHV-1 at 1 plaque-forming unit/cell in the presence or absence of unfractionated heparin (UFH), low-molecular-weight heparin (LMWH) or the PDE inhibitors, 3-isobutyl-1methylxanthine (IBMX), and cilostazol. We assessed platelet activation status in flow cytometric assays by measuring P-selectin expression. We found that all of the inhibitors blocked EHV-1- and thrombin-induced platelet activation in a dose-dependent manner. Platelet activation in PRP was maximally inhibited at concentrations of 0.05 U/mL UFH and 2.5 mug/mL LMWH. These concentrations represented 0.1-0.2 U/mL anti-factor Xa activity measured in chromogenic assays. Both IBMX and cilostazol showed maximal inhibition of platelet activation at the highest tested concentration of 50 muM, but inhibition was lower than that seen with UFH and LMWH. Our results indicate that heparin anticoagulants and strong non-selective (IBMX) or isoenzyme-3 selective (cilostazol) PDE antagonists inhibit ex vivo EHV-1-induced platelet activation. These drugs have potential as adjunctive therapy to reduce the serious complications associated with EHV-1-induced thrombosis. Treatment trials are warranted to determine whether these drugs yield clinical benefit when administered to horses infected with EHV-1.

Charting the interactome of PDE3A in human cells using an IBMX based chemical proteomics approach.[Pubmed:26205238]

Mol Biosyst. 2015 Oct;11(10):2786-97.

In the cell the second messenger cyclic nucleotides cAMP and cGMP mediate a wide variety of external signals. Both signaling molecules are degraded by the superfamily of phosphodiesterases (PDEs) consisting of more than 50 different isoforms. Several of these PDEs are implicated in disease processes inspiring the quest for and synthesis of selective PDE inhibitors, that unfortunately have led to very mixed successes in clinical trials. This may be partially caused by their pharmacological action. Accumulating data suggests that small differences between different PDE isoforms may already result in specific tissue distributions, cellular localization and different involvement in higher order signal protein complexes. The role of PDEs in these higher order signal protein complexes has only been marginally addressed, as no screening methodology is available to address this in a more comprehensive way. Affinity based chemical proteomics is a relatively new tool to identify specific protein-protein interactions. Here, to study the interactome of PDEs, we synthesized a broad spectrum PDE-capturing resin based on the non-selective PDE inhibitor 3-isobutyl-1-methylxanthine (IBMX). Chemical proteomics characterization of this resin in HeLa cell lysates led to the capture of several different PDEs. Combining the IBMX-resin with in-solution competition with the available more selective PDE inhibitors, cilostamide and papaverine, allowed us to selectively probe the interactome of PDE3A in HeLa cells. Besides known interactors such as the family of 14-3-3 proteins, PDE3A was found to associate with a PP2A complex composed of a regulatory, scaffold and catalytic subunit.

Chaetocin inhibits IBMX-induced melanogenesis in B16F10 mouse melanoma cells through activation of ERK.[Pubmed:26748310]

Chem Biol Interact. 2016 Feb 5;245:66-71.

Chaetocin is a natural product isolated from Chaetomium species that has anti-bacterial and anti-myeloma activities. In this study, we investigated the inhibitory effect of chaetocin on melanogenesis and the underlying mechanisms in B16F10 mouse melanoma cells. In the present study, chaetocin significantly inhibited IBMX-induced melanin production and tyrosinase activity without any cytotoxicity. Furthermore, chaetocin down-regulated both the protein and mRNA levels of tyrosinase, which is a specific enzyme that catalyzes the conversion of tyrosine to melanin. We also observed that the protein level of MITF was significantly reduced by chaetocin treatment. In addition, we found that the anti-melanogenic effect of chaetocin was suppressed by treatment with the specific ERK inhibitor (PD98059). Accordingly, chaetocin inhibited melanogenesis via suppressing the protein level of MITF followed by activation of the ERK signaling pathway. These data suggest that chaetocin may be a potential anti-melanogenic agent for use in skin-whitening cosmetics and a topical agent for treatment of hyperpigmentation disorders.

cAMP promotes the differentiation of neural progenitor cells in vitro via modulation of voltage-gated calcium channels.[Pubmed:24065885]

Front Cell Neurosci. 2013 Sep 19;7:155.

The molecular mechanisms underlying the differentiation of neural progenitor cells (NPCs) remain poorly understood. In this study we investigated the role of Ca(2+) and cAMP (cyclic adenosine monophosphate) in the differentiation of NPCs extracted from the subventricular zone of E14.5 rat embryos. Patch clamp recordings revealed that increasing cAMP-signaling with Forskolin or IBMX (3-isobutyl-1-methylxantine) significantly facilitated neuronal functional maturation. A continuous application of IBMX to the differentiation medium substantially increased the functional expression of voltage-gated Na(+) and K(+) channels, as well as neuronal firing frequency. Furthermore, we observed an increase in the frequency of spontaneous synaptic currents and in the amplitude of evoked glutamatergic and GABAergic synaptic currents. The most prominent acute effect of applying IBMX was an increase in L-type Ca(2+)currents. Conversely, blocking L-type channels strongly inhibited dendritic outgrowth and synapse formation even in the presence of IBMX, indicating that voltage-gated Ca(2+) influx plays a major role in neuronal differentiation. Finally, we found that nifedipine completely blocks IBMX-induced CREB phosphorylation (cAMP-response-element-binding protein), indicating that the activity of this important transcription factor equally depends on both enhanced cAMP and voltage-gated Ca(2+)-signaling. Taken together, these data indicate that the up-regulation of voltage-gated L-type Ca(2+)-channels and early electrical excitability are critical steps in the cAMP-dependent differentiation of SVZ-derived NPCs into functional neurons. To our knowledge, this is the first demonstration of the acute effects of cAMP on voltage-gated Ca(+2)channels in NPC-derived developing neurons.

Phosphodiesterase inhibitors suppress alpha2-adrenoceptor-mediated 5-hydroxytryptamine release from tracheae of newborn rabbits.[Pubmed:9726632]

Eur J Pharmacol. 1998 Jul 31;354(1):67-71.

The outflow of 5-hydroxytryptamine (5-HT) from isolated tracheae of newborn rabbits was determined by high pressure liquid chromatography with electrochemical detection. This 5-HT outflow reflects release from neuroendocrine epithelial cells of the airway mucosa, as previously shown. Phenylephrine, via alpha2B-adrenoceptors, caused a transient increase in 5-HT outflow, maximally by about 250%, an effect mediated by liberation of intracellular Ca2+, as previously shown. The non-selective phosphodiesterase inhibitor 2-isobutyl-1-methylxanthine (IBMX) concentration-dependently inhibited phenylephrine-induced 5-HT release (completely at 100 microM, IC50: 1.3 microM). Likewise, benzafentrine (inhibitor of phosphodiesterase 3 and 4) and siguazodan (inhibitor of phosphodiesterase 3) also almost completely inhibited phenylephrine-induced 5-HT release with IC50 values of 1.7 and 4.2 microM, respectively. Rolipram (inhibitor of phosphodiesterase 4), in a concentration of 10 microM, which exceeds more than 10-fold the reported IC50 for phosphodiesterase 4, did not significantly affect phenylephrine-induced 5-HT release. 5-HT release induced by depolarizing concentrations of K+ (45 mM), which largely depends on extracellular Ca2+, was not affected by IBMX. In conclusion, phosphodiesterases, with characteristics of phosphodiesterase 3, appear to play an important role in the control of cyclic nucleotide mediated inhibition of 5-HT release from neuroendocrine epithelial cells.

IBMX is a broad-spectrum phosphodiesterase (PDE) inhibitor, with IC50s of 6.5, 26.3 and 31.7 μM for PDE3, PDE4 and PDE5, respectively.

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