Synergism between long-acting bromocryptine microcapsules and cyclosporine A in the prevention of various autoimmune diseases in rats

Green tea catechins alleviate autoimmune symptoms and visual impairment in a murine model for human chronic intraocular inflammation by inhibiting Th17-associated pro-inflammatory gene expression

Autoimmune uveitis is a sight-threatening disease mainly caused by dysregulation of immunity. We investigated the therapeutic effects of green tea extract (GTE) and its major component, epigallocatechin-3-gallate (EGCG), on a murine model of experimental autoimmune uveoretinitis (EAU). Oral administration of GTE, EGCG, dexamethasone, or water, which started 5 days before the induction, was fed every two days to each group. On day 21 post induction, the eyes were examined by confocal scanning laser ophthalmoscopy, optical coherence tomography (OCT), fundus fluorescein angiography (FFA) and electroretinography (ERG) prior to sacrificing the animals for histological assessments and gene expression studies. Retinal-choroidal thicknesses (RCT) and major retinal vessel diameter were measured on OCT sections and FFA images, respectively. Comparing to water-treated EAU animals, GTE attenuated uveitis clinical manifestations, RCT increase (1.100 ± 0.013 times vs 1.005 ± 0.012 times, P < 0.001), retinal vessel dilation (308.9 ± 6.189 units vs 240.8 units, P < 0.001), ERG amplitudes attenuation, histopathological ocular damages, and splenomegaly in EAU mice. The therapeutic effects of GTE were dose dependent and were comparable to dexamethasone. EGCG, a major active constituent of GTE, partially alleviated uveitic phenotypes including recovering visual function. Th-17 associated pro-inflammatory gene [interleukin 1 beta (IL-1β), IL-6, IL-17A, and tumor necrosis factor alpha (TNF-α)] expressions were down regulated by GTE and EGCG treatments, which showed no detectable morphological defects in liver and kidney in non-induced and EAU mice. Our findings suggest that GTE consumption can serve as a potent therapeutic agent as well as a food supplement for developing alternative treatments against autoimmune uveitis.

Interaction of cytochrome P450 3A inhibitors with P-glycoprotein

Many clinically important drug interactions occur due to inhibition of human liver cytochrome P450 3A (CYP3A) metabolism. The drug efflux pump P-glycoprotein (Pgp) can be an additional locus contributing to these drug interactions because there is overlap in drugs that are substrates for both proteins. We screened a number of CYP3A inhibitors (macrolide antibiotics, azole antifungals, and ergotpeptides) for their ability to interact with Pgp, compared with prototypical Pgp inhibitors. We used cell lines expressing human, mouse, and rat mdr1 genes. Pgp antagonism was defined by interactions of the drugs with four cell lines (LLC-PK1, L-MDR1, L-mdr1a, and L-mdr1b) using a microfluorometric calcein-AM assay and characterized for their inhibitor constant (K(i)) toward calcein-AM. The compounds were further defined for their ability to inhibit MDR1 by their effect on vinblastine accumulation into L-MDR1 cells. Representative compounds from each class of drugs were further tested as Pgp substrates, defined by the ability of human Pgp or mouse mdr1a/Pgp to transport them across a polarized kidney epithelial cell in vitro. These same compounds were administered radiolabeled in vivo to mdr1a (+/+) and (-/-) mice and the distribution of radioactivity compared. The results are summarized as follows: 1) Some drug interactions with Pgp were substrate- and/or assay-dependent. 2) Ergot alkaloids were identified as a class of MDR1/Pgp chemosensitizers. 3) The Ergot alkaloids revealed species differences in the structure-activity relationships for inhibition of Pgp. Simultaneous inhibition of Pgp by many CYP3A inhibitors contributes to human variation in the extent of drug-drug interactions.

Bromocriptine treatment of systemic lupus erythematosus

Prolactin, a peptide hormone, acts as a cytokine. It has been hypothesized that bromocriptine, a dopamine analog that suppresses pituitary secretion of prolactin, suppresses circulating prolactin and, through this mechanism, has the potential to suppress autoimmune disease. This rationale has been applied to the treatment of systemic lupus erythematosus (SLE), a prototype autoimmune illness that occurs spontaneously in animal models such as the F1 hybrid NZBxNZW mouse, and in humans. Treatment with bromocriptine was effective in treating some induced and spontaneous autoimmune disease in experimental models. Bromocriptine did slow the course of SLE in NZBxNZW mice when treatment was started before the appearance of clinical disease. In addition, bromocriptine was effective in treating established disease in this model. In three separate clinical trials, bromocriptine showed evidence that it had a therapeutic effect in treating human lupus. Bromocriptine is currently considered an unproven therapy for SLE. Its use is entirely experimental. The fact that bromocriptine was effective in treating NZBxNZW mice, the beneficial therapeutic effects in human trials, and the low toxicity of the drug form a solid rationale for undertaking further therapeutic trials.

Upregulation of lymphocyte apoptosis as a strategy for preventing and treating autoimmune disorders: a role for whole-food vegan diets, fish oil and dopamine agonists

Induced apoptosis of autoreactive T-lymphocyte precursors in the thymus is crucial for the prevention of autoimmune disorders. IGF-I and prolactin, which are lymphocyte growth factors, may have the potential to suppress apoptosis in thymocytes and thus encourage autoimmunity; conversely, dietary fish oil rich in omega-3 fats appears to upregulate apoptosis in lymphocytes. Since whole-food vegan diets may downregulate systemic IGF-I activity, it is proposed that such a diet, in conjunction with fish oil supplementation and treatment with dopamine agonists capable of suppressing prolactin secretion, may have utility for treating and preventing autoimmune disorders. This prediction is consistent with the extreme rarity of autoimmune disorders among sub-Saharan black Africans as long as they followed their traditional quasi-vegan lifestyles, and with recent ecologic studies correlating risks for IDDM and for multiple sclerosis mortality with animal product and/or saturated fat consumption. Moreover, there is evidence that vegan or quasi-vegan diets are useful in the management of rheumatoid arthritis, multiple sclerosis, and possibly SLE. The dopamine agonist bromocryptine exerts anti-inflammatory effects in rodent models of autoimmunity, and there is preliminary evidence that this drug may be clinically useful in several human autoimmune diseases; better tolerated D2-specific agonists such as cabergoline may prove to be more practical for use in therapy. The moderate clinical utility of supplemental fish oil in rheumatoid arthritis and certain other autoimmune disorders is documented. It is not unlikely that extra-thymic anti-inflammatory effects contribute importantly to the clinical utility of vegan diets, bromocryptine, and fish oil in autoimmunity. The favorable impact of low latitude or high altitude on autoimmune risk may be mediated by superior vitamin D status, which is associated with decreased secretion of parathyroid hormone; there are theoretical grounds for suspecting that parathyroid hormone may inhibit apoptosis in thymocytes. Androgens appear to up-regulate thymocyte apoptosis, may be largely responsible for the relative protection from autoimmunity enjoyed by men, and merit further evaluation for the management of autoimmunity in women. It will probably prove more practical to prevent autoimmune disorders than to reverse them once established; a whole-food vegan diet, coupled with fish oil and vitamin D supplementation, may represent a practical strategy for achieving this prevention, while concurrently lowering risk for many other life-threatening 'Western' diseases.

Bromocriptine has little direct effect on murine lymphocytes, the immunomodulatory effect being mediated by the suppression of prolactin secretion

We investigated whether the immunosuppressive effect of bromocriptine in mice is due to its direct effect on lymphocyte functions or through inhibition of prolactin secretion. Incubation of mouse Babl/c splenic lymphocytes with bromocriptine in vitro at a concentration of around 0.5 to 1 microgram/mL causes an inhibition of antigen- or mitogen-induced proliferation. However, bromocriptine in vitro has no effect on lymphokine production (gamma-interferon and interleukin-2), expression of interleukin-2 receptor or lymphocyte cytotoxic function. Furthermore, treatment of Babl/c mice with bromocriptine inhibits the mixed lymphocyte reaction and mitogen stimulation, as well as primary and secondary antibody production. However, we postulated that the inhibition of ex vivo functional activity could not account for a direct cytostatic or cytotoxic effect of bromocriptine. This is supported by the in vitro data, which shows that bromocriptine has no effect on proliferating P-815 mastocytoma tumor cells. Finally, (NZB/NZW) F1 mice spontaneously develop a disease similar to systemic lupus erythematosus. In both non-autoimmune Babl/c mice and (NZB/NZW) F1 lupus-mice, the serum level of bromocriptine achieved by a treatment with 5 mg/kg on average is 2-6 ng/mL. On the one hand, this dose is sufficient to significantly alter the ex vivo functional tests in Babl/c mice and to show a beneficial effect in the in vivo model of female lupus-mice. On the other hand, the lowest concentration which could have an inhibitory effect on antigen- and mitogen-induced proliferation in vitro is 200 ng/mL, ie 50 times more than that required in vivo to obtain significant reductions of proteinurea, glomerular membrane proliferation and immune deposits in lupus-mice. The serum levels of gamma-interferon and interleukin-2 are reduced in lupus-mice when compared with Babl/c mice. The treatment with bromocriptine does not influence these parameters. In conclusion, our data demonstrate that the major immunosuppressive activity of bromocriptine is probably dependent on its hypoprolactinemic effect.