Involvement of Crosstalk Between cAMP and cGMP in Synaptic Plasticity in the Substantia Gelatinosa Neurons

Substantia gelatinosa (SG) neurons receive synaptic inputs from primary afferent Adelta- and C-fibers, where nociceptive information is integrated and modulated by numerous neurotransmitters or neuromodulators. A number of studies were dedicated to the molecular mechanism underlying the modulation of excitability or synaptic plasticity in SG neurons and revealed that second messengers, such as cAMP and cGMP, play an important role. Recently, cAMP and cGMP were shown to downregulate each other in heart muscle cells. However, involvement of the crosstalk between cAMP and cGMP in neurons is yet to be addressed. Therefore, we investigated whether interaction between cAMP and cGMP modulates synaptic plasticity in SG neurons using slice patch clamp recording from rats. Synaptic activity was measured by excitatory post-synaptic currents (EPSCs) elicited by stimulation onto dorsal root entry zone. Application of 1 mM of 8-bromoadenosine 3,5-cyclic monophosphate (8-Br-cAMP) or 8-bromoguanosine 3,5-cyclic monophosphate (8-Br-cGMP) for 15 minutes increased EPSCs, which were maintained for 30 minutes. However, simultaneous application of 8-Br-cAMP and 8-Br-cGMP failed to increase EPSCs, which suggested antagonistic cross-talk between two second messengers. Application of 3-isobutyl-1-methylxanthine (IBMX) that prevents degradation of cAMP and cGMP by blocking phosphodiesterase (PDE) increased EPSCs. Co-application of cAMP/cGMP along with IBMX induced additional increase in EPSCs. These results suggest that second messengers, cAMP and cGMP, might contribute to development of chronic pain through the mutual regulation of the signal transduction.

Safety Assessment of Octylmethoxycinnamate, Butylmethoxydibenzoylmethane, and Octyltriazone Sunscreens by Human Repeated Insult Patch Tests to Compare the Shelanski and Maximization Tests / 대한피부과학회지

BACKGROUND: Human repeated insult patch tests (HRIPTs) are a final method for safety assessment of chemical ingredients. In the representative HRIPTs, the Shelanski and modified Draize require 200 participants, but the maximization and modified maximization tests require only 25. OBJECTIVE: To evaluate the safety of three sunscreen ingredients using the Shelanski and maximization methods. METHODS: Octylmethoxycinnamate, butylmethoxydibenzoylmethane, and octyltriazone (BASF) were prepared for the induction, as 25% ointment in white petrolatum base. After a 2-3 week resting phase, patch and photopatch tests were conducted, but pretreatment with SLS was only performed in the maximization test. The results were analyzed using the Chi-Square test. RESULTS: During the induction phase, there were only two (4%) weak positive reactions observed with the Shelanski method, whereas all 25 displayed strong or extremely positive reactions with the maximization method. Butylmethoxydibenzoylmethane displayed the most frequent elicitation reactions; the patch and photopatch tests displayed weak positive reactions in four (2%) and six (3%), and in one (4%) and two (8%), with the Shelanski and maximization tests, respectively. Taking into account two of the six reactors displayed positive reactions to petrolatum with the Shelanski test, the actual number of positive patch test reactions would be four (2%). The difference in results of the two methods was not statistically significant. CONCLUSION: Although it is not easy to conduct HRIPT on 200 subjects, and the results from the two tests were not significantly different, the reactions from the maximization tests were too severe to be recommended in humans.

Safety and Efficacy of Itraconazole for the Treatment of Onychomycosis in the Diabetic Population / 대한피부과학회지

INTRODUCTION: As the number of diabetics increase with younger onset and longer duration, patients are confronted with higher incidence of diabetes related complications such as distal extremity vasculopathy, neuropathy and various infectious diseases. Such diabetics are more prone to a much higher rate of onychomycosis compared to normal subjects and because this could trigger irreversible consequences, confirmation of fungal involvement should be promptly taken care of. Itraconazole is a widely used drug nowadays and compared to drugs such as griseofulvin and ketoconazole, has many advantages in efficacy, cost, duration of therapy which eventually results in better patient compliance. OBJECTIVE: Our study was designed to better dictate the usage of itraconazole in diabetics so these patient can receive quality treatment when it is needed. METHOD: The study consisted of 101 patients with both onychomycosis and diabetes who were receiving treatment in Eulji hospital. They all received 3 pulses of itraconazole and were evaluated for efficacy and safety of their treatment. The patients were observed on routine examinations for 36 weeks and at their visits they were interviewed and received microscopic examinations. RESULT: Eighty four percent of the patients showed clinical and mycological improvement with 33% of them showing total clearance. There were no hypo- or hyperglycemic events and 17 patients complained of mostly mild side effects such as indigestion. Two patients dropped out of the study due to epigastric pain and peripheral extremity swelling. CONCLUSION: The use of itraconazole in the treatment of onychomycosis seemed to be effective and relatively safe for diabetics.

Constitutive expression and changes of cytochrome P450 isozymes mRNAs by vehicles (petrolatum, DMSO, ethanol) in rat skin using semi-quantitative RT-PCR

Many drugs are primarily metabolized by the cytochrome P450s (CYPs). Drug metabolites would be important allergens for adverse drug reactions such as drug eruptions. Skin tests with a suspected drug have conducted to identify causative drugs of drug eruptions, with vehicles such as white petrolatum, DMSO, ethanol. This study will compare the expression of rat CYP isozyme mRNAs between the skin and the liver, with examining an effect of the vehicles on the cutaneous CYPs using semi-quantitative RT-PCR. Thirty-two Sprague-Dawley rats between the ages of six and eight weeks were divided as four groups. One group was used to compare the constitutive mRNA expression between skin and liver, while the others were to examine the effects of three vehicles. The ratios of expression of CYP1A2, CYP2B1/2, CYP2E1, CYP3A1, and CYP4A1 were significantly higher in the liver than the skin. However, CYP1A1 and CYP2C11 were higher in the skin than liver. The effects of vehicles were quite different; white petrolatum significantly induced CYP1A1 (p=0.012) and CYP2C11 mRNAs, while ethanol inhibited CYP1A1 and CYP2B1/2. DMSO did not make any changes. The results suggest that rat skin can participate in drug metabolism with their own CYP isozymes. The effects of vehicles on the cutaneous CYP expression should not be ignored and may be applied for determination of an appropriate vehicle for certain drug(s).

Studies for Pathogenesis of Fixed Drng Emptions Through the Change of Cytochrome p450 Isozymes / 대한피부과학회지

The reasons of same site recurrence in fixed drug eruptions (FDEs) remain to be clarified. Although the nature of antigen in FDE is unknown, drug metabolites could play a role for antigen formation. Cytochrome p450 isozymes (CYPs) are important enzymes for drug metabolism. This study was done to examine the role of CYPs in FDEs. Provoked lesion was compared with non-provoked lesion by the same drug on the same patient to overcome inter-individual variations of CYPs. The reverse transcriptase-polymerase chain reaction (RT-PCR) with primers for CYPs and the immunohistochemistry (IHC) with anti-CYPs, pancytokeratin, and leukocyte common antigen (LCA) antibodies were conducted. The causative drugs were different in 13 patients who conducted RT-PCR, and the result could not be analyzed by the cause. The levels of CYP2C8/19 and CYP2E1 mRNAs increased significantly in provoked lesions. The keratinocytes in cases of mefenamic acid-induced FDEs stained strongly with anti-CYP2C9 antibody not with the other three antibodies (CYP1A1, CYP2E1, and CYP3A4). The FDE cases from doxycycline, which is not metabolized by CYP2C9 enzyme, and those from chlormezanone did not react to anti-CYP2C9 antibody. The cells stained with CYP antibodies did not react with anti-LCA antibody but with anti-pancytokeratin antibody. The number of cells which reacted to anti-LCA antibody clearly increased in the provoked lesions, regardless of the cause. The above results suggest that CYPs may contribute the drug antigen formation and different levels of CYPs between provoked and non-provoked lesions can play a role for the same site recurrence of lesions in FDEs.