UV irradiation causes multiple cellular changes in cultured human retinal pigment epithelium cells

BACKGROUND

The retinal pigment epithelium maybe causally involved in the development and progression of age-related macula degeneration; however, the mechanisms leading to the development of age-related macula degeneration remain largely unknown. The purpose of this study was to examine cellular changes in the retinal pigment epithelium induced by direct irradiation with UV light in culture.

METHODS

Retinal pigment epithelium cells from post-mortem human retinas were used to obtain dissociated cultures with cells retaining the ability to differentiate in vitro. These cells were cultured over several days to weeks. The UV radiation (UV-A and UV-B) occurred under sterile conditions with a 100 HBO/mercury bulb attached to a dissecting microscope, delivering co-axial illumination. The time dependence of irradiation effects was analysed using morphometric, immunohistochemical, functional and apoptosis-detecting techniques.

RESULTS

Vital and proliferating retinal pigment epithelium cell cultures could be prepared consistently. The cells showed tissue-specific morphologies in vitro for several days to weeks. Pigment epithelium-derived factor was detected in these cells using immunocytochemistry and Western blots. The UV irradiation but not white light resulted in measurable alterations of cell shape and size. The irradiated cells showed partial swelling and shrinkage reminiscent of progressing apoptotic degeneration. TUNEL staining revealed that apoptosis was induced by UV light, but not detectably by white light. The phagocytosis of fluorescent micro-particles diminished after irradiation. These effects were dependent on the duration of irradiation.

CONCLUSIONS

Cultures of retinal pigment epithelium are suitable and sensitive models to study cell damage and may contribute to unravelling the pathogenetic mechanisms of retinal degeneration.

Molecular and pharmacological evidence for modulation of kinin B(1) receptor expression by endogenous glucocorticoids hormones in rats

1. The effect of endogenous glucocorticoid hormones on the expression of rat B(1) receptors was examined by means of molecular and pharmacological functional approaches. 2. Rats were adrenalectomized (ADX), and 7 days after this procedure the intradermal injection of B(1) receptor agonist des-Arg(9)-BK produced a significant increase in the paw volume, while only a weak effect was observed in sham-operated animals. A similar increase in the contractile responses mediated by B(1) agonist des-Arg(9)-BK was also observed in the rat portal vein in vitro. 3. Chemical ADX performed with mitotane (a drug that reduces corticosteroid synthesis) produced essentially the same up-regulation of B(1) receptors as that observed in ADX rats. 4. The modulation of B(1) receptor expression was evaluated by ribonuclease protection assay, employing mRNA obtained from the lungs and paw of ADX rats. 5. Additionally, both paw oedema and contraction of portal vein mediated by B(1) agonist des-Arg(9)-BK in ADX rats, were markedly inhibited by treatment with dexamethasone, or COX-2 inhibitor meloxican, or with the NF-kappaB inhibitor PDTC. Interestingly, the same degree of inhibition was achieved when the animals were treated with a combination of submaximal doses of dexamethasone and PDTC. 6. The involvement of NF-kappaB pathway was further confirmed by mobility shift assay using nuclear extracts from lung, paw and heart of ADX rats. It was also confirmed that the treatment of ADX rats with dexamethasone, PDTC or dexamethasone plus PDTC completely inhibit NF-kappaB activation caused by absence of endogenous glucucorticoid. 7. Together, the results of the present study provide, for the first time, molecular and pharmacological evidence showing that B(1) kinin receptor expression can be regulated through endogenous glucocorticoids by a mechanism dependent on NF-kappaB pathway. Clinical significance of the present findings stem from evidence showing the importance of B(1) kinin receptors in the mediation of inflammatory and pain related responses.

Anti-hyperalgesic properties of the extract and of the main sesquiterpene polygodial isolated from the barks of Drymis winteri (Winteraceae)

This study analyses the anti-hyperalgesic properties of the hydroalcoholic extract (HE) and the sesquiterpene polygodial isolated from the barks of Drymis winteri (Winteraceae). The HE (10 to 60 mg kg(-1), i.p. or 100 to 600 mg kg(-1), p.o.), 4 h prior, produced significant inhibition of abdominal constrictions caused by i.p. injection of acetic acid, kaolin and zymosan in mice. The mean ID50s were: 21.4, 33.7 and 36.6 mg kg(-1); 173.0, 123.0 and 366.0 mg kg(-1), by i.p. and by oral route, respectively. This effect lasted for up to 8 h. The HE at the same range of doses produced dose-related inhibition of both phases of the formalin-induced licking. The calculated mean ID50s values for the early phase were: 26.1 and 43.0 mg kg(-1), while for the late phase they were 7.3 and 72.7 mg kg(-1), respectively, when given by i.p. and by oral route. The HE (10 to 60 mg kg(-1), i.p. or 25 to 200 mg kg(-1), p.o.), 4 h prior, produced significant inhibition of capsaicin-induced neurogenic pain with mean ID50 values of 18.0 and 68.0 mg kg(-1), respectively. The HE (3 to 100 mg kg(-1), p.o., 1 h) inhibited in a graded manner, the hyperalgesia induced by bradykinin (3 nmol/paw) or substance P (10 nmol/paw) in rat paw, with mean ED50 values of 54.5 and 53.7 mg kg(-1), respectively. However, the HE did not affect the hyperalgesia induced by carrageenan or PGE2. When assessed in the hot-plate test, the HE (200 mg kg(-1), p.o.) was inactive. Naloxone (1 mg kg(-1), i.p.) significantly reversed the antinociceptive effects caused by either morphine (5 mg kg(-1), s.c.) or by HE (60 mg kg(-1), i.p.). Polygodial (0.1 to 10 mg kg(-1), i.p.) produced significant inhibition of acetic acid, kaolin and zymosan-induced writhing in mice, being about 14 to 27-fold more potent than the HE at the ID50 level. Together these data provide support for a long-lasting anti-hyperalgesic property for the active principle(s) present in the barks of D. winteri when assessed in several models of inflammatory or neurogenic pain. Its actions involve, at least in part, an interaction with opioid pathway through a naloxone-sensitive mechanism, seeming not to be related with a non-specific peripheral or central depressant actions. Finally, the sesquiterpene polygodial isolated from this plant, appears to be mainly responsible for the anti-hyperalgesic properties of the extract.

Anti-allergic effects and oedema inhibition caused by the extract of Drymis winteri

OBJECTIVE

To study the acute anti-inflammatory and anti-allergic properties of an extract of D. winteri.

MATERIAL AND METHODS

Paw oedema induced in rats with various stimuli and anaphylactic shock in mice.

RESULTS

The hydroalcoholic extract (HE) of D. winteri (Winteraceae) (30 to 100 mg/kg, p.o., 1 h prior) inhibited carrageenan (300 micrograms/paw) and dextran (100 micrograms/paw)-induced paw oedema formation in a dose-dependent manner, with mean ID50 values of 49 and < 30 mg/kg, respectively. The HE of D. winteri (30 to 100 mg/kg) also inhibited paw oedema induced by bradykinin (BK) (3 nmol), substance P (SP) (10 nmol) and PAF-acether (PAF) (10 nmol), in a dose-dependent manner, with mean ID50 values of 56, 63, and 58 mg/kg, respectively. However, the HE inhibited the rat paw oedema induced by prostaglandin E2 (PGE2) (10 nmol) (29 +/- 7 and 33 +/- 2% at 60 and 240 min) to a smaller extent, and had no effect on oedema elicited by histamine (100 nmol). In adrenalectomized animals, the inhibition by the HE of D. winteri (100 mg/kg, p.o., 1 h prior) of BK-elicited oedema (3 nmol/paw) was significantly smaller when compared with that observed in control animals. When assessed in rats actively sensitised to ovalbumin (OVO), the oedema caused by OVO (6 micrograms/paw) was significantly inhibited by HE of D. winteri (30 to 100 mg/kg, p.o.), with a mean ID50 of about 65 mg/kg. The HE of D. winteri (100 and 200 mg/kg, p.o.) significantly increased survival rate when assessed in anaphylactic shock in mice actively sensitised to the antigen. The protective effect was long-lasting, being observed for up to 15 h. Dexamethasone, used as positive control (0.5, 1 and 2 mg/kg) produced a long-lasting (up to 24 h) increase in the survival rate of the animals.

CONCLUSIONS

These results confirm and extend our previous studies, and demonstrate the clear oral anti-inflammatory and anti-allergic properties of the active principle(s) present in the barks of D. winteri, thus confirming its reported medicinal use in folk medicine for the management of airway diseases.