Effects of subminimal inhibitory concentrations of minocycline on neutrophil chemotactic factor production in comedonal bacteria, neutrophil phagocytosis and oxygen metabolism

In vivo tissue response and antibacterial efficacy of minocycline delivery system based on polymethylmethacrylate bone cement

This study aims the in vivo biological characterization of an innovative minocycline delivery system, based on polymethylmethacrylate bone cement. Bone cements containing 1% or 2.5% (w/w) minocycline were formulated and evaluated through solid-state characterization. Biological evaluation was conducted in vivo, within a rat model, following the subcutaneous and bone tissue implantation, and tissue implantation associated with Staphylococcus aureus is challenging. The assessment of the tissue/biomaterial interaction was conducted by histologic, histomorphometric and microtomographic techniques. Minocycline addition to the composition of the polymethylmethacrylate bone cement did not modify significantly the cement properties. Drug release profile was marked by an initial burst release followed by a low-dosage sustained release. Following the subcutaneous tissue implantation, a reduced immune-inflammatory reaction was verified, with diminished cell recruitment and a thinner fibro-connective capsule formation. Minocycline-releasing cements were found to enhance the bone-to-implant contact and bone tissue formation, following the tibial implantation. Lastly, an effective antibacterial activity was mediated by the implanted cement following the tissue challenging with S. aureus. Kinetic minocycline release profile, attained with the developed polymethylmethacrylate system, modulated adequately the in vivo biological response, lessening the immune-inflammatory activation and enhancing bone tissue formation. Also, an effective in vivo antibacterial activity was established. These findings highlight the adequacy and putative application of the developed system for orthopedic applications.

Do tetracyclines and erythromycin exert anti-acne effects by inhibition of P450-mediated degradation of retinoic acid?

For decades, retinoic acid (RA) is known as the most potent therapeutic option in the therapy of acne and altered homeostasis of endogenous retinoids has been discussed in the context of acne pathogenesis. Besides retinoids, antibiotics such as tetracyclines or erythromycin are well established in acne pharmacotherapy. Accumulating evidence points towards common molecular pathways being targeted by both RA and anti-acne antibiotics; however, a precise 'common denominator' connecting these chemically diverse anti-acne agents has not yet been identified. Interestingly, tetracyclines are associated with the occurrence of pseudotumor cerebri, a rare neurological side effect otherwise associated with retinoid intoxication or RA exposure. This association at the clinical level suggests an interaction between tetracyclines and endogenous RA signalling. As erythromycin does not cross the blood brain barrier, CNS side effects are not to be expected, yet not precluding a possible local interaction of erythromycin with endogenous RA metabolism in the skin. We hypothesize tetracyclines and erythromycin to locally inhibit endogenous RA metabolism in the skin and thus mimic therapeutic action of RA. This readily testable hypothesis suggests inhibition of endogenous RA metabolism and amplification of endogenous RA signalling as a mechanism underlying the biochemical actions of antibiotics in acne therapy. Elucidation of such interactions may ultimately enhance our understanding of acne therapy and pathogenesis and may yield a sound, scientific basis for hypothesis-driven development of novel therapeutic compounds.

The Role of the Antioxidative Defense System in Papulopustular Acne

Acne vulgaris frequently occurs in the second decade of life. The pathogenesis of the disease is multifactorial. In this study, we aimed to investigate the role of reactive oxygen species in inflammation of acne by determining the activity of antioxidant defense enzymes in leukocytes. Fifty-two patients with papulopustular type acne vulgaris and 36 healthy controls were enrolled. The severity of the disease was examined by the Global Acne Grading System, and the activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT) enzymes as well as the level of thiobarbituric acid reactive substance (TBARS) were detected in leukocytes. The activities of SOD and GSH-Px were significantly decreased in the acne group. CAT activity and TBARS level were higher in patients than controls. Only a poor correlation was detected between GSH-Px activity and severity of the disease. Antioxidative defense enzymes are impaired in papulopustular acne, and drugs with antioxidative effects might be valuable in treatment.

Minocycline controls clinical outcomes and inflammatory cytokines in moderate and severe meibomian gland dysfunction

PURPOSE

To assess clinical outcomes and tear cytokine levels in patients with moderate and severe meibomian gland dysfunction (MGD) after treatment with oral minocycline and artificial tears versus artificial tears only.

DESIGN

Prospective, randomized clinical trial.

METHODS

Sixty eyes of 60 patients with stage 3 or 4 meibomian gland dysfunction were enrolled. We evaluated the tear film break-up time, Schirmer test results, corneal and conjunctival fluorescein staining results, biomicroscopic examination results of lid margins and meibomian glands, and tear cytokine levels before and after 1 month and 2 months of oral minocycline and artificial tears (group 1) or artificial tears only (group 2). Tear samples were collected and analyzed using a BD Cytometric Bead Array (BD Bioscience, San Jose, California, USA) for detection of interleukin (IL)-1β, IL-6, IL-7, IL-8, IL-12p70, IL-17α, interferon-γ, tumor necrosis factor-α, and monocyte chemotactic protein-1. The Wilcoxon signed-rank test, Mann-Whitney U test, generalized linear model, and linear mixed model were performed.

RESULTS

Patients in group 1 showed statistically significant improvement in all clinical signs and symptoms after 1 month and 2 months of treatment. Patients of group 1 showed more significant improvement compared with those in group 2. Patients in group 1 also showed statistically significant reductions in IL-6, IL-1β, IL-17α, tumor necrosis factor-α, and IL-12p70 after 2 months of treatment.

CONCLUSIONS

Oral minocycline can provide clinical benefits in treating moderate and severe meibomian gland dysfunction by reducing inflammatory cytokine levels.

Non-antibiotic properties of tetracyclines as anti-allergy and asthma drugs

All available therapies for human allergic disease target IgE mediated pathologic responses after IgE has been produced. We are developing tetracyclines as anti-allergy drugs to prevent IgE production, based on our findings that minocycline or doxycycline treatment of allergic asthmatic humans significantly improves their asthma symptoms, reduces their oral steroid requirements, and strongly suppresses their ongoing IgE responses (ELISA, mast cell mediated cutaneous late phase responses); the tetracyclines also strongly suppress peak IgE responses of BPO-KLH sensitized mice (ELISPOT assay, ELISA, skin tests). The antibiotic activity of the tetracyclines is not required for suppression of IgE responses; inclusion of minocycline or doxycycline in sterile culture prevents anti-CD40/IL-4 mediated induction of memory IgE responses by PBMC of allergic asthmatic patients (ELISA), and induction of specific memory IgE responses by spleen cells of BPO-KLH sensitized mice (ELISPOT assay, ELISA). The tetracyclines affect an epsilon specific pathway because IgM, IgG and IgA responses did not decrease. Further, in humans, DTH responses to recall antigens did not decrease. In related studies, we found that two distinct T cell subsets: CD4+CD60 negative and CD8+CD60+ (CD60 is a ganglioside) (humans) and CD4+ Asialo GM1 ganglioside negative and CD8+Asialo GM1 ganglioside+ (mice), both are required for induction of memory IgE responses. Phosphorylated (phos) p38 MAP kinase, but not phos ERK or phos JNK expression by CD4+ and CD8+, including CD8+CD60+, T cells is increased in allergic asthmatic humans, as is IL-4 and IL-10 production. The tetracyclines appear to target T cell pathways to induce suppression of IgE responses because they suppress phos p38 MAP kinase expression by both CD4+ and CD8+, including CD8+CD60+, T cell subsets, and IL-4 and IL-10, while upregulating IL-2 and IFN gamma, and suppressing IgE responses. Our finding that tetracyclines do not require antibiotic activity to suppress IgE responses opens the door to development of new tetracycline-based and other therapeutics for human allergic disease.

Tetracycline-mediated IgE isotype-specific suppression of ongoing human and murine IgE responses in vivo and murine memory IgE responses induced in vitro

We previously reported that minocycline treatment of allergic asthmatic patients had oral steroid sparing effects and improved their clinical status and that minocycline suppressed in vitro induction of IgE responses by their PBMC. The effect of minocycline on human or animal IgE responses in vivo has not been studied. Allergic asthmatics (serum IgE: 505 +/- 535 IU ml(-1)) were given minocycline (150 mg po to 250 mg po BID) as add-on therapy to standard care for up to 10 months; control subjects (IgE: 405 +/- 472 IU ml(-1)) received standard care (n = 6 per group). Serum immunoglobulin (IgM, IgG, IgE and IgA) levels were determined monthly (Nephelometry, Unicap Total IgE Fluoroenzyme immunoassay). BALB/c mice (n = 6 per group) were injected intraperitoneally with benzylpenicilloyl(14)-Keyhole limpet hemocyanin (BPO(14)-KLH) in alum on days 0, 21 and 42, fed with minocycline or doxycycline (10-100 mg kg(-1)) on day 44 and numbers of BPO-specific IgG(1), IgE and IgA antibody-forming cell (AFC) in mesenteric LN and spleen and serum immunoglobulin levels were determined on days 46-70 (enzyme-linked immunosorbent spot assay, ELISA). The ability of minocycline or doxycycline to suppress in vitro induction of murine memory IgE responses also was investigated. Minocycline strongly suppressed serum IgE levels of allergic asthmatics (9% per month) (P = 0.012). Minocycline (and doxycycline) also strongly suppressed peak murine IgE AFC and serum IgE responses (>95, approximately 75%, respectively) and in vitro induction of memory IgE responses by murine mesenteric LN and spleen cells (>95%). Tetracycline suppression of all human and murine IgE responses was IgE isotype specific. Suppression of murine IgE responses in vivo was dose dependent and lasted 5-7 days.

Meibomian gland function and the tear lipid layer

The meibomian glands of the lid produce a lipid material whose synthesis is dependent on neuronal, hormonal, and vascular factors. This lipid material is fluid, spreads easily, is a surfactant as well as an aqueous barrier and must remain functional after a blink. To satisfy these requirements, the meibomian lipids have a specific composition. Even after delivery it may be modified by lipases produced by ocular bacteria, and modifications in the lipid components can lead to unique disease states. For example, bacteria may degrade lipids, producing an unstable tear film and irritating free fatty acids; and hormonal imbalances may alter lipid profiles to destabilize the tear film and produce evaporative dry eye.

Minocycline modulates neuroinflammation independently of its antimicrobial activity in staphylococcus aureus-induced brain abscess

Minocycline exerts beneficial immune modulatory effects in several noninfectious neurodegenerative disease models; however, its potential to influence the host immune response during central nervous system bacterial infections, such as brain abscess, has not yet been investigated. Using a minocycline-resistant strain of Staphylococcus aureus to dissect the antibiotic's bacteriostatic versus immune modulatory effects in a mouse experimental brain abscess model, we found that minocycline significantly reduced mortality rates within the first 24 hours following bacterial exposure. This protection was associated with a transient decrease in the expression of several proinflammatory mediators, including interleukin-1beta and CCL2 (MCP-1). Minocycline was also capable of protecting the brain parenchyma from necrotic damage as evident by significantly smaller abscesses in minocycline-treated mice. In addition, minocycline exerted anti-inflammatory effects when administered as late as 3 days following S. aureus infection, which correlated with a significant decrease in brain abscess size. Finally, minocycline was capable of partially attenuating S. aureus-dependent microglial and astrocyte activation. Therefore, minocycline may afford additional therapeutic benefits extending beyond its antimicrobial activity for the treatment of central nervous system infectious diseases typified by a pathogenic inflammatory component through its ability to balance beneficial versus detrimental inflammation.

Changes in the tear film and ocular surface from dry eye syndrome

Dry eye syndrome (DES) refers to a spectrum of ocular surface diseases with diverse and frequently multiple aetiologies. The common feature of the various manifestations of DES is an abnormal tear film. Tear film abnormalities associated with DES are tear deficiency, owing to insufficient supply or excessive loss, and anomalous tear composition. These categorizations are artificial, as in reality both often coexist. DES disrupts the homeostasis of the tear film with its adjacent structures, and adversely affects its ability to perform essential functions such as supporting the ocular surface epithelium and preventing microbial invasion. In addition, whatever the initial trigger, moderate and severe DES is characterized by ocular surface inflammation, which in turn becomes the cause and consequence of cell damage, creating a self-perpetuating cycle of deterioration. Progress has been made in our understanding of the aetiology and pathogenesis of DES, and these advances have encouraged a proliferation of therapeutic options. This article aims to amalgamate prevailing ideas of DES development, and to assist in that, relevant aspects of the structure, function, and production of the tear film are reviewed. Additionally, a synopsis of therapeutic strategies for DES is presented, detailing treatments currently available, and those in development.

Effects of minocycline on the ocular flora of patients with acne rosacea or seborrheic blepharitis

PURPOSE

To assess the effect of minocycline on the ocular flora in patients with acne rosacea or blepharitis.

METHODS

A total of ten patients were enrolled in this prospective study, with six patients diagnosed with acne rosacea with concomitant meibomianitis, two patients with acne rosacea without concomitant ocular involvement, and two patients with seborrheic blepharitis. The eyelids and conjunctiva of both eyes were cultured before the initiation of systemic minocycline therapy, after 3 months of active therapy, and 3 months after the discontinuation of therapy. Isolated bacteria were identified and quantified, and antibiotic susceptibility was determined.

RESULTS

The colony-forming units (CFU) isolated from the eyelids significantly decreased after a 3-month treatment with minocycline (P = 0.0013). The CFU significantly increased to approach that of the baseline with the discontinuation of minocycline (P = 0.0275). The most common isolated bacteria, including coagulase-negative Staphylococcus (CNS), Staphylococcus aureus (S. aureus), and Propionibacterium acne (P. acne), except for corynebacterium, had a significant decrease in bacterial count with minocycline therapy compared with baseline (P < 0.05). There was a trend in the decrease of bacterial CFU isolated from the conjunctiva with minocycline therapy, although this was not statistically significant (P = 0.1955). Four of the ten patients carried tetracycline-resistant CNS strains, but none of the S. aureus or P. acne isolated at baseline was resistant to tetracycline. All six patients with acne rosacea and concomitant meibomianitis had marked clinical improvement.

CONCLUSION

Minocycline effectively decreased eyelid bacterial flora in patients with acne rosacea or blepharitis. One of the mechanisms of newer generation tetracycline analogues may be a decrease or elimination of bacterial flora from the eyelids.

Minocycline effect on meibomian gland lipids in meibomianitis patients

The objective of this research was to determine the effect of oral minocycline on the meibomian gland nonpolar and free fatty acid lipids of chronic blepharitis patients. Patients--seborrheic blepharitis (SBBL), acne rosacea (AR) without ocular involvement, and acne rosacea with meibomianitis (AR-MKC). Minocycline treatment--50mg orally for 2 weeks followed by 100mg to the end of 3 months; this was followed by 3 more months with no treatment. Meibomian gland secretions (meibum) were collected before treatment, at the end of the 3 months on treatment, and 3 months after stopping treatment. Lipids were separated and analyzed for wax and sterol esters, triglycerides, diglycerides, free cholesterol and free fatty acids. Data were analyzed statistically by ANOVA. Minocycline treatment resulted in decreased diglycerides and free fatty acids in the group AR-MKC, which continued into the second 3 months (off treatment) and was significant. Cholesterol decreased, but triglycerides initially decreased with treatment and then increased when treatment in the group was discontinued (second 3 months); these results, however, were not significant. Thus, minocycline has its greatest effect on lipid types, which result from degradation (lipase) reactions, suggesting a lipase inhibition effect and/or direct effect on ocular flora. This minocycline effect continues even after treatment is discontinued, suggesting a more lasting effect on ocular microflora. Minocycline may be most effective when the treatment period is longer than 3 months. These results give insight into disease mechanisms associated with chronic blepharitis.

Treatment of recurrent auricle pseudocyst with intralesional injection of minocycline: a report of two cases

Pseudocyst of the auricle (PCA) is characterized by asymptomatic and fluctuant swelling of the external ear and frequent relapses despite various therapeutic approaches. We describe two patients with recurrent PCA who were successfully treated with intralesional injection of 1 mg/mL of minocycline hydrochloride (minocycline), 2 or 3 times at 2-week intervals. Intralesional injection of minocycline may be a new therapeutic choice for conservative management of PCA, especially in recurrent cases. The mechanisms of minocycline action that may have led to reduction of the cystic lesions are discussed.

Sensitivity of Propionibacterium acnes isolated from acne patients: comparative study of antimicrobial agents

The antimicrobial susceptibility of Propionibacterium acnes isolated before and after treatment of acne patients was measured. The four female and three male acne patients were treated with an oral acne medication, roxithromycin or minocycline, and/or a topical acne medication, nadifloxacin cream or clindamycin hydrochloride lotion for 1-8 weeks. The isolated strains were tested for their susceptibility to the antimicrobial action of: nadifloxacin, ofloxacin, erythromycin, clindamycin hydrochloride, tetracycline hydrochloride, minocycline, doxycycline, ampicillin, cephalexin and gentamycin. No resistant strains of P. acnes were observed.

Clinical evaluation of roxithromycin in patients with acne

On the basis of reports that erythromycin is effective in the treatment of acne, we investigated whether roxithromycin (ROM), a new derivative of erythromycin, might also be effective in treating acne. Roxithromycin was administered to 30 patients with acne for 8 weeks. General improvement was assessed 8 weeks after the initiation of the therapy with a six-graded scale as follows; 1: good improvement, 2: moderate improvement, 3: slight improvement, 4: no change, 5: worsening, and 6: no assessment. The percentage of good or moderate improvement was 73.3%, and that of good improvement alone was 20.0%. Our results suggest that ROM is effective in the treatment of acne.