Tetracycline-induced mitohormesis mediates disease tolerance against influenza.

Mitohormesis defines the increase in fitness mediated by adaptive responses to mild mitochondrial stress. Tetracyclines inhibit not only bacterial but also mitochondrial translation, thus imposing a low level of mitochondrial stress on eukaryotic cells. We demonstrate in cell and germ-free mouse models that tetracyclines induce a mild adaptive mitochondrial stress response (MSR), involving both the ATF4-mediated integrative stress response and type I interferon (IFN) signaling. To overcome the interferences of tetracyclines with the host microbiome, we identify tetracycline derivatives that have minimal antimicrobial activity, yet retain full capacity to induce the MSR, such as the lead compound, 9-tert-butyl doxycycline (9-TB). The MSR induced by doxycycline (Dox) and 9-TB improves survival and disease tolerance against lethal influenza virus (IFV) infection when given preventively. 9-TB, unlike Dox, did not affect the gut microbiome and also showed encouraging results against IFV when given in a therapeutic setting. Tolerance to IFV infection is associated with the induction of genes involved in lung epithelial cell and cilia function, and with downregulation of inflammatory and immune gene sets in lungs, liver, and kidneys. Mitohormesis induced by non-antimicrobial tetracyclines and the ensuing IFN response may dampen excessive inflammation and tissue damage during viral infections, opening innovative therapeutic avenues.

Amphiphilic tetracationic porphyrins are exceptionally active antimicrobial photosensitizers: In vitro and in vivo studies with the free-base and Pd-chelate.

Antimicrobial photodynamic inactivation (aPDI) employs the combination of nontoxic photosensitizing dyes and visible light to kill pathogenic microorganisms regardless of drug-resistance, and can be used to treat localized infections. A meso-substituted tetra-methylpyridinium porphyrin with one methyl group replaced by a C12 alkyl chain (FS111) and its Pd-derivative (FS111-Pd) were synthesized and tested as broad-spectrum antimicrobial photosensitizers when excited by blue light (5 or 10 J/cm2 ). Both compounds showed unprecedented activity, with the superior FS111-Pd giving 3 logs of killing at 1 nM, and eradication at 10 nM for Gram-positive methicillin-resistant Staphylococcus aureus. For the Gram-negative Escherichia coli, both compounds produced eradication at 100 nM, while against the fungal yeast Candida albicans, both compounds produced eradication at 500 nM. Both compounds could be categorized as generators of singlet oxygen (ΦΔ = 0.62 for FS111 and 0.71 for FS111-Pd). An in vivo study was carried out using a mouse model of localized infection in a partial thickness skin abrasion caused by bioluminescent Gram-negative uropathogenic E. coli. Both compounds were effective in reducing bioluminescent signal in a dose-dependent manner when excited by blue light (405 nm), but aPDI with FS111-Pd was somewhat superior both during light and in preventing recurrence during the 6 days following PDT.

Neonatal vitamin A injection promotes cattle muscle growth and increases oxidative muscle fibers.

BACKGROUND: Vitamin A and its metabolite, retinoic acid (RA), are important regulators of cell differentiation and organ morphogenesis. Its impact on beef cattle muscle growth remains undefined. METHOD: Angus steer calves were administrated with 0 (control) or 150,000 IU vitamin A (retinyl palmitate in glycerol, i.m.) per calf at birth and 1 month of age. At 2 months of age, a biopsy of the Biceps femoris muscle was obtained to analyze the immediate effects of vitamin A injection on myogenic capacity of muscle cells. The resulting steers were harvested at 14 months of age. RESULTS: Vitamin A administration increased cattle growth at 2 months. At 2 months of age, Vitamin A increased PAX7 positive satellite cells and the expression of myogenic marker genes including PAX7, MYF5, MYOD and MYOG. Muscle derived mononuclear cells were further isolated and induced myogenesis in vitro. More myotubes and a higher degree of myogenesis was observed in vitamin A groups. Consistently, vitamin A increased Latissimus dorsi (LD) muscle fiber size at harvest. In addition, vitamin A increased the ratio of oxidative type I and type IIA fibers and reduced the glycolic type IIX fibers. Furthermore, we found that RA, a key bioactive metabolite of vitamin A, activated PPARGC1A promoter, which explains the upregulated expression of PPARGC1A in skeletal muscle. CONCLUSION: Vitamin A administration to neonatal calves enhanced postnatal muscle growth by promoting myogenesis and increasing satellite cell density, accompanied with a shift to oxidative muscle fibers.

Vitamin A administration at birth promotes calf growth and intramuscular fat development in Angus beef cattle.

BACKGROUND: Marbling, or intramuscular fat, is an important factor contributing to the palatability of beef. Vitamin A, through its active metabolite, retinoic acid, promotes the formation of new fat cells (adipogenesis). As intramuscular adipogenesis is active during the neonatal stage, we hypothesized that vitamin A administration during the neonatal stage would enhance intramuscular adipogenesis and marbling. METHODS: Angus steer calves (n = 30), in a completely randomized design, were randomly allotted to three treatment groups at birth, receiving 0, 150,000, or 300,000 IU of vitamin A at both birth and one month of age. A biopsy of the biceps femoris muscle was collected at two months of age. After weaning at 210 d of age, steers were fed a backgrounding diet in a feedlot until 308 d of age, when they were transitioned to a high concentrate finishing diet and implanted with trenbolone/estradiol/tylosin mixture. Steers were harvested at an average of 438 d of age. All diets were formulated to meet nutrient requirements. RESULTS: Weaning weight and weight during the backgrounding phase were linearly increased (P <  0.05) by vitamin A level, though no difference in body weight was observed at harvest. Intramuscular fat of steers at 308 d of age, measured by ultrasound, quadratically increased (P <  0.05) with vitamin A level from 4.0±0.26 % to 4.9±0.26 %. Similarly, carcass marbling score in the ribeye quadratically increased (P < 0.05). CONCLUSION: Administration of vitamin A at birth increased weaning weight and enhanced marbling fat development. Thus, vitamin A administration provides a practical method for increasing marbling and early growth of beef cattle.

Nutrigenomic regulation of adipose tissue development - role of retinoic acid: A review.

To improve the efficiency of animal production, livestock have been extensively selected or managed to reduce fat accumulation and increase lean growth, which reduces intramuscular or marbling fat content. To enhance marbling, a better understanding of the mechanisms regulating adipogenesis is needed. Vitamin A has recently been shown to have a profound impact on all stages of adipogenesis. Retinoic acid, an active metabolite of vitamin A, activates both retinoic acid receptors (RAR) and retinoid X receptors (RXR), inducing epigenetic changes in key regulatory genes governing adipogenesis. Additionally, Vitamin D and folates interact with the retinoic acid receptors to regulate adipogenesis. In this review, we discuss nutritional regulation of adipogenesis, focusing on retinoic acid and its impact on epigenetic modifications of key adipogenic genes.

Structure-activity relationship of the aminomethylcyclines and the discovery of omadacycline.

A series of novel tetracycline derivatives were synthesized with the goal of creating new antibiotics that would be unaffected by the known tetracycline resistance mechanisms. New C-9-position derivatives of minocycline (the aminomethylcyclines [AMCs]) were tested for in vitro activity against Gram-positive strains containing known tetracycline resistance mechanisms of ribosomal protection (Tet M in Staphylococcus aureus, Enterococcus faecalis, and Streptococcus pneumoniae) and efflux (Tet K in S. aureus and Tet L in E. faecalis). A number of aminomethylcyclines with potent in vitro activity (MIC range of ≤0.06 to 2.0 µg/ml) were identified. These novel tetracyclines were more active against one or more of the resistant strains than the reference antibiotics tested (MIC range, 16 to 64 µg/ml). The AMC derivatives were active against bacteria resistant to tetracycline by both efflux and ribosomal protection mechanisms. This study identified the AMCs as a novel class of antibiotics evolved from tetracycline that exhibit potent activity in vitro against tetracycline-resistant Gram-positive bacteria, including pathogenic strains of methicillin-resistant S. aureus (MRSA) and vancomycin-resistant enterococci (VRE). One derivative, 9-neopentylaminomethylminocycline (generic name omadacycline), was identified and is currently in human trials for acute bacterial skin and skin structure infections (ABSSSI) and community-acquired bacterial pneumonia (CABP).

Use of intravitreal triamcinolone for the treatment of optic nerve edema in a patient with acute retinal necrosis: case report.

PURPOSE: To report the use of combined intravitreal triamcinolone and foscarnet therapy in a patient with active acute retinal necrosis. METHODS: Retrospective case report. A 40-year-old white woman with a history of ulcerative proctitis, intolerant to oral steroids, developed an aggressive case of acute retinal necrosis complicated by severe optic nerve edema resulting in 20/200 vision. RESULTS: Intravitreal foscarnet provided an initial improvement of the vitritis and retinitis; however, optic nerve edema and 20/200 vision persisted. After 2 weeks, intravitreal triamcinolone was combined with the foscarnet dose. Four days later, the optic nerve edema had resolved, the vision returned to 20/40, and the herpetic infection remained controlled. Eight months later, the patient had not experienced a retinal detachment, and acuity was 20/20. Oral steroids are an accepted adjunct to antiviral therapy in acute retinal necrosis; however, combined intravitreal steroid and antiviral therapy has not been previously reported. After combined intravitreal therapy was attempted, the patient experienced a rapid resolution of symptoms without exacerbating her retinitis. CONCLUSION: In select patients, combined intravitreal triamcinolone and foscarnet may be effective in treating acute retinal necrosis and its inflammatory sequelae.

In vitro and in vivo antimalarial efficacies of optimized tetracyclines.

With increasing resistance to existing antimalarials, there is an urgent need to discover new drugs at affordable prices for countries in which malaria is endemic. One approach to the development of new antimalarial drugs is to improve upon existing antimalarial agents, such as the tetracyclines. Tetracyclines exhibit potent, albeit relatively slow, action against malaria parasites, and doxycycline is used for both treatment (with other agents) and prevention of malaria. We synthesized 18 novel 7-position modified tetracycline derivatives and screened them for activity against cultured malaria parasites. Compounds with potent in vitro activity and other favorable drug properties were further tested in a rodent malaria model. Ten compounds inhibited the development of cultured Plasmodium falciparum with a 50% inhibitory concentration (IC50) after 96 h of incubation of <30 nM, demonstrating activity markedly superior to that of doxycycline (IC50 at 96 h of 320 nM). Most compounds showed little mammalian cell cytotoxicity and no evidence of in vitro phototoxicity. In a murine Plasmodium berghei model, 13 compounds demonstrated improved activity relative to that of doxycycline. In summary, 7-position modified tetracyclines offer improved activity against malaria parasites compared to doxycycline. Optimized compounds may allow lower doses for treatment and chemoprophylaxis. If safety margins are adequate, dosing in children, the group at greatest risk for malaria in countries in which it is endemic, may be feasible.

Effect of ensilation of potato on viability of Taenia hydatigena eggs.

A Taenia hydatigena model was used to assess the effect 0, 7, 14, 21, and 28 days of ensilation of minced potato on viability of tapeworm eggs. For infection of lambs, 2,000 T. hydatigena eggs were ensiled for 0, 7, 14, 21 and 28 days in minced potato at 22°C and fed to recently weaned lambs (29.9±0.76 kg). At slaughter, no cysticerci were recovered from lambs infected with eggs ensiled for 28 days while a mean of 5.0±5.0 cysticerci (0.25% of the initial egg dose) were recovered from lambs infected with eggs ensiled for 21 days. For lambs fed eggs ensiled for 0 days (control), 359.3±55.6 cysticerci were recovered (18.0% of the initial egg dose). Regression analysis revealed that a 99.9% reduction in viability was attained after 18.59 days of ensilation.

Effect of heat treatment on viability of Taenia hydatigena eggs.

Effects of heat treatments on activation and infectivity of Taenia hydatigena eggs were assessed. Eggs containing oncospheres were used for in vitro and in vivo studies to determine the response to 5min of heat treatment, ranging from room temperature (22°C) to 60°C. The study demonstrated 99.47% and 100% reduction in oncosphere activation or infectivity after 5min of heat treatment at 60°C and 57.38°C under in vitro and in vivo conditions, respectively. Similar results between the two approaches indicted the appropriateness of the in vitro methods to identify oncosphericidal treatments of practical significance. Similar heat treatments may also be effective against Taenia saginata and help to reduce occurrence of beef cysticercosis.

Airway epithelial NF-κB activation promotes Mycoplasma pneumoniae clearance in mice.

BACKGROUND/OBJECTIVE: Respiratory infections including atypical bacteria Mycoplasma pneumoniae (Mp) contribute to the pathobiology of asthma and chronic obstructive pulmonary disease (COPD). Mp infection mainly targets airway epithelium and activates various signaling pathways such as nuclear factor κB (NF-κB). We have shown that short palate, lung, and nasal epithelium clone 1 (SPLUNC1) serves as a novel host defense protein and is up-regulated upon Mp infection through NF-κB activation in cultured human and mouse primary airway epithelial cells. However, the in vivo role of airway epithelial NF-κB activation in host defense against Mp infection has not been investigated. In the current study, we investigated the effects of in vivo airway epithelial NF-κB activation on lung Mp clearance and its association with airway epithelial SPLUNC1 expression. METHODOLOGY/MAIN RESULTS: Non-antimicrobial tetracycline analog 9-t-butyl doxycycline (9-TB) was initially optimized in mouse primary tracheal epithelial cell culture, and then utilized to induce in vivo airway epithelial specific NF-κB activation in conditional NF-κB transgenic mice (CC10-(CA)IKKß) with or without Mp infection. Lung Mp load and inflammation were evaluated, and airway epithelial SPLUNC1 protein was examined by immunohistochemistry. We found that 9-TB treatment in NF-κB transgene positive (Tg+), but not transgene negative (Tg-) mice significantly reduced lung Mp load. Moreover, 9-TB increased airway epithelial SPLUNC1 protein expression in NF-κB Tg+ mice. CONCLUSION: By using the non-antimicrobial 9-TB, our study demonstrates that in vivo airway epithelial NF-κB activation promotes lung bacterial clearance, which is accompanied by increased epithelial SPLUNC1 expression.

The history of the tetracyclines.

The history of the tetracyclines involves the collective contributions of thousands of dedicated researchers, scientists, clinicians, and business executives over the course of more than 60 years. Discovered as natural products from actinomycetes soil bacteria, the tetracyclines were first reported in the scientific literature in 1948. They were noted for their broad spectrum antibacterial activity and were commercialized with clinical success beginning in the late 1940s to the early 1950s. The second-generation semisynthetic analogs and more recent third-generation compounds show the continued evolution of the tetracycline scaffold toward derivatives with increased potency as well as efficacy against tetracycline-resistant bacteria, with improved pharmacokinetic and chemical properties. Their biologic activity against a wide spectrum of microbial pathogens and their uses in mammalian models of inflammation, neurodegeneration, and other biological systems indicate that the tetracyclines will continue to be successful therapeutics in infectious diseases and as potential therapeutics against inflammation-based mammalian cell diseases.

Brief communication: Mass spectroscopic characterization of tetracycline in the skeletal remains of an ancient population from Sudanese Nubia 350-550 CE.

Histological evidence of tetracycline use has been reported in an ancient X-Group population (350-550 CE) from Sudanese Nubia (Bassett et al., 1980). When bone samples were examined by fluorescent microscopy under UV light at 490 A yellow-green fluorophore deposition bands, similar to those produced by tetracycline, were observed, suggesting significant exposure of the population to the antibiotic. These reports were met skeptically with claims that the fluorescence was the result of postmortem taphonomic infiltration of bacteria and fungi. Herein, we report the acid extraction and mass spectroscopic characterization of the antibiotic tetracycline from these samples. The bone samples were demineralized in anhydrous hydrogen fluoride which dissolved the bone-complexed tetracycline, followed by isolation by solid phase extraction on reverse-phase media. Chemical characterization by high pressure liquid chromatography mass-spectroscopic procedures showed that the retention times and mass spectra of the bone extract were identical to tetracycline when treated similarly. These results indicate that a natural product tetracycline was detectable within the sampled bone and was converted to the acid-stable form, anhydrotetracycline, with a mass + H of 427.1 amu. Our findings show that the bone sampled is labeled by the antibiotic tetracycline, and that the NAX population ingested and were exposed to tetracycline-containing materials in their dietary regime.

Virtual reality simulation in acquiring and differentiating basic ophthalmic microsurgical skills.

OBJECTIVE: A virtual reality (VR) surgical simulator (EyeSi ophthalmosurgical simulator: VRMagic, Mannheim, Germany) was evaluated as a part-task training platform for differentiating and developing basic ophthalmic microsurgical skills. METHODS: Surgical novice performance (residents, interns, and nonmicrosurgical ophthalmic staff) was compared with surgical expert performance (practicing ophthalmic microsurgeons) on a basic navigational microdexterity module provided with the EyeSi simulator. RESULTS: Expert surgeons showed a greater initial facility with all microsurgical tasks. With repeated practice, novice surgeons showed sequential improvement in all performance scores, approaching but not equaling expert performance. CONCLUSION: VR simulator performance can be used as a gated, quantifiable performance goal to expert-level benchmarks. The EyeSi is a valid part-task training platform that may help develop novice surgeon dexterity to expert surgeon levels.

Taenia taeniaeformis: effectiveness of staining oncospheres is related to both temperature of treatment and molecular weight of dyes utilized.

Methods to determine viability of taeniid oncospheres following treatments with potential lethality have practical application in efforts to control transmission. Here we investigated several methods, in lieu of infectivity studies, to assess oncosphere viability and determine lethal temperature treatment regimens. In the first experiment, a standard treatment to exshell oncospheres with 0.5% hypochlorite was assessed for influence on oncosphere recovery of Taenia taeniaeformis eggs. Recovery of eggs and exshelled oncospheres decreased with increasing time in hypochlorite, which indicated that hypochlorite can damage eggs and oncospheres, translating into potential overestimation of lethality of experimental treatments. Losses in hypochlorite were accentuated when eggs were pretreated at 75 degrees C, but not lower temperatures, including 65 degrees C, indicating a sharp threshhold between 65 degrees C and 75 degrees C where eggs and oncospheres became hypersensitive to subsequent hypochlorite treatment. To further investigate this change in relation to temperature, non-vital (acridine orange, AO) and vital (propidium iodide, PI; trypan blue, TB) dyes were used to assess staining of oncospheres (exshelled or not) under conditions ranging from room temperature up to 95 degrees C. The behaviors of dyes as related to internal staining of oncospheres were described using non-linear regression and a sigmoid four-parametric model to determine the inflection point (T50). Each of the dyes differed significantly in T50 estimates, e.g. AO (69.22+/-0.53), PI (73.89+/-0.52) and TB (79.43+/-0.45). For these dyes, the T50 increased in relation to the increasing molecular weight of the dyes. Collectively, the results suggested that barriers to chemical permeability exist in eggs that breakdown incrementally with increasing temperatures above 65 degrees C. This staining behavior and the likelihood that the temperatures involved are above a lethal threshhold clarify a basic limitation in the use of vital dyes to assess oncosphere viability. The results may be relevant to other Taenia spp.

Silencing and un-silencing of tetracycline-controlled genes in neurons.

To identify the underlying reason for the controversial performance of tetracycline (Tet)-controlled regulated gene expression in mammalian neurons, we investigated each of the three components that comprise the Tet inducible systems, namely tetracyclines as inducers, tetracycline-transactivator (tTA) and reverse tTA (rtTA), and tTA-responsive promoters (P(tets)). We have discovered that stably integrated P(tet) becomes functionally silenced in the majority of neurons when it is inactive during development. P(tet) silencing can be avoided when it is either not integrated in the genome or stably-integrated with basal activity. Moreover, long-term, high transactivator levels in neurons can often overcome integration-induced P(tet) gene silencing, possibly by inducing promoter accessibility.

Optical coherence tomography of chronic solar retinopathy.

PURPOSE: To describe the optical coherence tomographic findings in eight eyes of four patients with chronic solar retinopathy. All patients had a history of sun gazing months to years prior to presentation. DESIGN: Retrospective case series. METHODS: Patients were examined using biomicroscopy performed by two or more experienced vitreoretinal specialists. All eight eyes had optical coherence tomography performed at the time of initial examination. RESULTS: All patients had a history of sun gazing and decreased vision in both eyes. On biomicroscopy, all eyes had a small, irregularly-shaped lamellar defect in the foveal center. No posterior vitreous detachment was present in any eye. Optical coherence tomography revealed a hyporeflective space at the level of the outer neurosensory retina and retinal pigment epithelium in all eyes. CONCLUSION: Optical coherence tomography demonstrates a characteristic hyporeflective space in the outer retina in patients with chronic solar retinopathy. These findings correlate with the histopathology of this condition and may be a useful clinical tool in confirming its diagnosis.

Infectious and presumed noninfectious endophthalmitis after intravitreal triamcinolone acetonide injection.

PURPOSE: To report potentially distinguishing characteristics between bacterial endophthalmitis and presumed noninfectious endophthalmitis associated with intravitreal triamcinolone acetonide injection. METHODS: Records of two patients with culture-proven bacterial endophthalmitis and six patients with presumed noninfectious endophthalmitis from intravitreal triamcinolone acetonide injections were analyzed retrospectively. RESULTS: Two eyes in two patients with culture-proven bacterial endophthalmitis had decreased vision and hypopyon or vitritis, but no pain or conjunctival injection 2 weeks after intravitreal triamcinolone acetonide injection. Seven eyes in six patients with presumed noninfectious endophthalmitis had blurred vision, hypopyon, and variable pain all within 2 days of intravitreal triamcinolone injection. All seven eyes were followed up closely and had rapid resolution of hypopyon and symptoms. CONCLUSION: Bacterial endophthalmitis after intravitreal triamcinolone acetonide injection may present in an atypical, relatively delayed manner with decreased vision but no pain or redness. Presumed noninfectious endophthalmitis presents within 2 days after the injection, may be accompanied by discomfort, and has a hypopyon that may be the triamcinolone material itself or a sterile inflammatory reaction. In these eyes, the hypopyon and symptoms quickly resolve without treatment.