Effectiveness of antimicrobial photodynamic therapy with a single treatment of RLP068/Cl in an experimental model of Staphylococcus aureus wound infection.

BACKGROUND: Chronic leg ulceration is a common health problem. It is well known that a clinically relevant bacterial load in chronic cutaneous wounds interferes significantly with the normal process of healing. Staphylococcus aureus is the most important representative of the staphylococcal group which causes clinically relevant infections within immunocompetent patients. OBJECTIVES: To investigate the efficacy of a single treatment of antimicrobial photodynamic therapy (APDT) with RLP068/Cl in a mouse model of a surgical wound infection induced with a methicillin-resistant strain of S. aureus (MRSA). METHODS: Wounds, established through the panniculus carnosus of BALB/c and CD1 mice, were inoculated with 5 x 10(7) c.f.u. of MRSA. Mice were randomized into four groups respectively receiving no treatment, APDT with placebo, APDT with a new phthalocyanine derivative (RLP068/Cl) and intraperitoneal teicoplanin. RESULTS: On day 2 from infection, a strong reduction of bacterial counts (≈ 3 logs) was observed in mice treated with RLP068/Cl in comparison with infected untreated mice. On day 9 from infection, a comparable and significant (≈ 2 logs) reduction of bacterial counts was found in mice treated with RLP068/Cl or with teicoplanin. At this time, histological examinations revealed that wounds treated with RLP068/Cl showed a complete re-epithelialization with a continuous epithelial lining. CONCLUSIONS: The results of the in vivo study demonstrated that APDT with RLP068/Cl may be useful in the management of chronic infected wounds, accelerating the repair process through a significant bacterial inhibition.

Role of muscarinic receptor subtypes in central antinociception.

1. The ability to modify the pain threshold by the two M1-muscarinic agonists: McN-A-343 and AF-102B and by the specific M2-agonist arecaidine was examined in mice and rats by using three different noxious stimuli: chemical (writhing test), thermic (hot-plate test) and mechanical (paw pressure test). 2. In the mouse hot-plate test McN-A-343 (20-50 micrograms per mouse i.c.v.) and AF-102B (1-10 mg kg-1 i.p.) produced significant antinociception which was prevented by atropine (1 microgram per mouse i.c.v.) and by the two selective M1 antagonists: pirenzepine (0.01 micrograms per mouse i.c.v.) and dicyclomine (0.08 micrograms per mouse i.c.v. or 10 mg kg-1 i.p.) but not by the specific M2-antagonist AFDX-116 (0.1 micrograms per mouse i.c.v.), naloxone (1 mg kg-1 i.p.) or by the acetylcholine (ACh) depletor hemicholinium-3 (HC-3) (1 micrograms per mouse i.c.v.). McN-A-343 and AF-102B were able to increase the pain threshold also in the mouse acetic acid writhing test and in rat paw pressure test. These antinociceptive effects were completely prevented by dicyclomine (0.08 micrograms per mouse i.c.v. or 10 mg kg-1 i.p.) but not by AFDX-116 (0.1 microgram per mouse or rat i.c.v.). 3. In contrast with the M1-agonists, the M2-agonist arecaidine (0.1-2 micrograms per mouse or rat i.c.v.) did not induce antinociception in all three analgesic tests. However, arecaidine, at the same i.c.v. doses, was able to reduce the pain threshold in the hot-plate and paw pressure tests.4. The site of muscarinic control of the pain threshold is localized in the CNS since drugs which do not cross the blood-brain barrier such as McN-A-343, pirenzepine and arecaidine exerted their effects only if injected i.c.v.5. On the basis of the above findings and existing literature we suggest that the postsynaptic muscarinic receptors involved in antinociception belong to the M1 subtype. Nevertheless, presynaptic autoreceptors (M2 subtype) may play a role in pain regulation since they are involved in modulation of endogenous ACh release.

Skin-photosensitizing properties of Zn(II)-2(3), 9(10), 16(17), 23(24)-tetrakis-(4-oxy-N-methylpiperidinyl) phthalocyanine topically administered to mice.

A Zn-phthalocyanine derivative bearing four 4-oxy-N-methyl-piperidinyl peripheral substituents has been formulated in an azone-containing gel for topical administration and its potential as a photodynamic therapy agent has been investigated. The phthalocyanine displays an intense absorbance in the 680 nm range and shows a high photosensitizing activity toward a model biological substrate (N-acetyl-L-tryptophanamide). Upon administration of 20 microg cm(-2) onto the dorsal skin of Balb/c mice, maximal phthalocyanine concentrations (ca. 64.2 ng mg(-1) of skin) are reached at 1 h after the deposition. The photosensitizer appears to be localized in the epidermal layers, since (a) no detectable amounts of phthalocyanine are recovered from the mouse blood and liver; and (b) upon photoactivation with a diode laser at 675 nm, only the epidermis is heavily damaged, as shown by histological and ultrastructural analysis. The photodamage is largely of inflammatory nature and an essentially complete healing of the damaged skin is observed at 72 h after the end of the phototreatment. The minimal phototoxic dose for 20 microg cm(-2) photosensitizer and 675 nm irradiation is found to be (150 mW cm(-2)-120 J cm(-2)) or (180 mW cm(-2)-100 J cm(-2)).

Effect of dietary fat, starch and cellulose on fecal bile acids in mice.

The effect of dietary fat, starch and cellulose on individual and total fecal bile acids was studied in mice after 4 wk of feeding diets containing different levels of fat (5 and 29%), starch (3, 36 and 57-65%) and cellulose (2 and 10%). Diet affected the fecal concentration of deoxycholic acid, beta-muricholic acid and total bile acids. Increasing dietary fat from 5 to 29% significantly increased the level of deoxycholic acid and total bile acids. An increase in dietary cellulose from 2 to 10% significantly decreased the level of deoxycholic acid, beta-muricholic acid and total bile acids. High levels of dietary starch (36 and 57-65%) did not significantly affect the excretion of deoxycholic, beta-muricholic and total fecal bile acids. Starch was able to bind bile acids in vitro and to affect the level of fecal free bile acids. In high fat diets, the level of free bile acids was lower in the feces of animals fed 36% starch diets than in those fed 3% starch diets. This reduction of free bile acids was accompanied by a reduction in colon proliferative activity. We suggest that free, rather than total, bile acids are the effective damaging agents for colon mucosa, and may represent a risk factor in the development of cancer.

Antinociceptive effect of R-(+)-hyoscyamine on the conjunctival reflex test in rabbits.

R-(+)-Hyoscyamine (1-10 microg/kg, s.c.) dose-dependently increased the local anesthetic effect of procaine (50 microg/ml) and lidocaine (50 microg/ml) in the conjunctival reflex test in the rabbit. This potentiating effect is completely prevented by the M1 antagonist dicyclomine (10 mg/kg, s.c.). The intensity of R-(+)-hyoscyamine antinociception was comparable to that induced by morphine (2 mg/kg, s.c.) and minaprine (15 mg/kg, s.c.), used as analgesic reference drugs. In the same experimental conditions, the S-(-)-enantiomer of atropine (0.1-10 microg/kg, s.c.), was completely ineffective. The present results confirm the ability of R-(+)-hyoscyamine to produce a paradoxical antinociceptive effect mediated by a cholinergic mechanism not only in rodents but also in the rabbit.

Synthesis and antinociceptive activity of some novel nonpeptide derivatives of interleukin-1 beta (193-195) sequence.

The synthesis of a new series of nonpeptide derivatives of interleukin-1 beta sequence is described. Compounds have been investigated for their relative activity regarding antinociception and suppression of inflammation. Several compounds with R1(R)Lys [CH2N]-Pro structure showed better efficacy in the inflamed paw pressure test than indometacin and morphine. In terms of the relative potencies the above mentioned products (i.e. compounds 2, 4, 5, 6; ED50 values of 0.002, 0.0035, 0.0032, 0.0074 mg/kg i.p. respectively) were 10-100 times more potent than indometacin and morphine (ED50 values of 0.22 and 0.75 mg/kg). Compounds 1-14 were not able to inhibit binding of labeled interleukin-1 beta to EL 4-6.1 murine cells, since they had no affinity for interleukin-1 beta receptors. The antinociceptive activity elicited by compound 4 in the rat inflamed paw pressure test was inhibited by naloxone, but the compound was inactive in the mouse hot plate and rat paw pressure tests. These results suggest that compound 4 exerts its antinociceptive activity through a mechanism which is based on the local release of endogenous opioids in injured tissue.