Phosphodiesterase Inhibitors

Two isoforms of ADPglucose pyrophosphatase/phosphodiesterase (AGPPase) have been characterized using barley leaves (Hordeum vulgare L.). Whilst one of the isoforms, designated as soluble AGPPase1 (SAGPPase1), is soluble in low ionic strength buffers, the other, SAGPPase2, is extractable using cell wall hydrolytic enzymes or high salt concentration solutions, thus indicating that it is adventitiously bound to the cell wall. Both AGPPase isoforms are highly resistant to SDS, this characteristic being utilized to purify them to homogeneity after zymographic detection of AGPPase activity in SDS-containing gels. N-terminal and internal amino acid sequencing analyses revealed that both SAGPPase1 and SAGPPase2 are distinct oligomers of the previously designated HvGLP1, which is a member of the ubiquitously distributed group of proteins of unknown function designated as germin-like proteins (GLPs).

To assess the effects of a single 100-mg dose of sildenafil citrate on visual function in men with early-stage age-related macular degeneration. Randomized double-blind placebo-controlled clinical trial. Nine men (mean age 71 years, range 59-85 years) with early-stage (minimal visual impairment and large drusen in the macula) age-related macular degeneration and 20/40 or better-corrected visual acuity in at least one eye were prospectively randomized to receive either placebo or sildenafil citrate (Viagra; Pfizer Inc, New York, New York) 100 mg as a single oral dose. After 7-14 days, they received the alternate treatment. Subjects underwent visual acuity, Amsler grid, color discrimination (D15), traffic light, Humphrey perimetry, and photo-stress testing in each eye before and at specific intervals within 8 hours after dosing. Compared with placebo, no pattern of errors were evident in any visual function test following sildenafil administration. No statistically or clinically relevant changes from baseline were observed in visual acuity, Humphrey perimetry (corrected pattern standard deviation), D15 color discrimination, or photo-stress tests. No clinically relevant changes were observed in the Amsler grid or traffic light tests. Sildenafil treatment was associated with transient mild or moderate headache, flushing, and rhinitis. There were no visual adverse events spontaneously reported to the investigator. A single 100-mg dose of sildenafil was well tolerated and produced no acute visual effects or exacerbation of preexisting visual impairment in nine men with early-stage age-related macular degeneration.

There is a high prevalence of erectile dysfunction (ED) in men with epilepsy; however, few studies have been conducted concerning the treatment of ED in this neurological group. The main purpose of this review is to highlight the influence of phosphodiesterase type 5 inhibitor (PDEI-5) for ED on seizure susceptibility. All available online articles with information pertaining to PDEI-5 and seizure susceptibility were included in this review. The main outcome assessed demonstrated the intriguing role of PDEI-5 and its metabolites on seizure susceptibility. Case reports in men without epilepsy described seizure occurrence and electrophysiological changes following sildenafil, tadalafil, or vardenafil treatment. Consistent with these findings, preclinical studies suggested a proconvulsant effect of PDEI-5 on models of seizure induction. Evidence suggests an influence of PDEI-5 on seizure susceptibility in humans. In addition, preclinical studies have demonstrated the role of nitric oxide metabolites in the facilitation of paroxysmal phenomenon. Although there are many causes of seizures, medical professionals should be aware of the possible influence of PDEI-5 on seizure susceptibility. Further investigation by physicians and scientists is required to improve our understanding of this important topic.

Cyclic nucleotide phosphodiesterases (PDE) are the enzymes catalyzing the hydrolysis and inactivation of the second messengers, cAMP and cGMP. Eleven PDE families are described to date, and selective inhibitors of some PDEs families are currently used in clinic for treating cardiovascular disorders, erectile dysfunction, and pulmonary hypertension. Isoforms of the PDE4 family are involved in smooth muscle contraction and inflammation. PDE4 selective inhibitors are currently in clinical trials for the treatment of diseases related to inflammatory disorders. Because of their myorelaxant properties, we first examined their expression in human myometrium and uncover an increased expression of one specific isoform, PDE4B2, in the near-term myometrium as compared to myometrium in the nonpregnant state. Using human myometrial cells in culture, we demonstrated that PDE4B2 can be induced by its own substrate, under the control of one of the major utero-contractile agonists, PGE2, itself upre...

Medical approaches to sexual difficulties prioritise the physical aspects of sexuality over other aspects, locating 'disorders' primarily in the anatomy, chemistry or physiology of the body. In accordance with this perspective on sexual matters, physicians look to physical interventions (for example, hormones, drugs, and surgery) to treat any 'abnormalities'. Following the discovery of popular--and profitabl-e-sexuopharmaceuticals such as sildenafil citrate (Viagra) for the treatment of erectile difficulties affecting men, the medical model has gained increasing influence in the domain of sexual health and well-being. However, while medical definitions of--and interventions related to--sexual difficulties are underpinned by an understanding of a 'universal' body (that is, an essential biological body that transcends culture and history), and by the categorisation of the normal and the pathological, the accounts of users of Viagra, and their sexual partners, d...

Methylxanthines of either natural or synthetic origin have a number of interesting pharmacological features. Proposed mechanisms of methylxanthine-induced pharmacological effects include competitive antagonism of G-coupled adenosine A1 and A2A receptors and inhibition of phosphodiesterases. A number of studies have indicated that methylxanthines also exert effects through alternative mechanisms, in particular via activation of sarcoplasmic reticulum or endoplasmic reticulum ryanodine receptor (RyR) channels. More specifically, RyR channel activation by methylxanthines was reported (1) to stimulate the process of excitation coupling in muscle cells, (2) to augment the excitability of neurons and thus their capacity to release neurotransmitters, and also (3) to improve their survival. Here, we address the mechanisms by which methylxanthines control RyR activation and we consider the pharmacological consequences of this activation, in muscle and neuronal cells. KeywordsCalcium-Methylxa...