Minocycline attenuates neuronal cell death and improves cognitive impairment in Alzheimer's disease models

Minocycline in the treatment of patients with primary sclerosing cholangitis: results of a pilot study

OBJECTIVES

Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease of young adults that is associated with significant morbidity and mortality. No effective medical therapy is available. Minocycline has been found to exert biological effects independent of its antimicrobial properties, including anti-inflammatory activities such as inhibition of inducible nitric oxide synthase, upregulation of interleukin 10, and direct suppressive effect on B- and T-cell function. Minocycline may also inhibit cell death pathways by reducing both proapoptotic and proinflammatory enzyme activation. We sought to investigate the safety and efficacy of minocycline among patients with PSC.

METHODS

We evaluated the efficacy of minocycline in patients with PSC in a pilot study. Sixteen patients with PSC were enrolled. Minocycline, 100 mg orally twice daily, was given for 1 year.

RESULTS

A statistically significant improvement in serum alkaline phosphatase activity (330 U/l vs. 265 U/l, P=0.04) and Mayo risk score (0.55 vs. 0.02, P=0.05) occurred with treatment. Serum bilirubin and albumin remained essentially unchanged while on treatment.

CONCLUSIONS

The results of this pilot study indicate that minocycline is reasonably well tolerated and potentially effective in patients with PSC. These findings might be explained by the anti-inflammatory and antiapoptotic properties of minocycline. Though the data presented are too preliminary to support the clinical use of minocycline in the treatment of PSC at this time, its use should be further investigated.

Inhibitory modulation of the mitochondrial permeability transition by minocycline

The semi-synthetic tetracycline derivative minocycline exerts neuroprotective properties in various animal models of neurodegenerative disorders. Although anti-inflammatory and anti-apoptotic effects are reported to contribute to the neuroprotective action, the exact molecular mechanisms underlying the beneficial properties of minocycline remain to be clarified. We analyzed the effects of minocycline in a cell culture model of neuronal damage and in single-channel measurements on isolated mitoplasts. Treatment of neuron-enriched cortical cultures with rotenone, a high affinity inhibitor of the mitochondrial complex I, resulted in a deregulation of the intracellular Ca2+-dynamics, as recorded by live cell imaging. Minocycline (100 microM) and cyclosporin A (2 microM), a known inhibitor of the mitochondrial permeability transition pore, decreased the rotenone-induced Ca2+-deregulation by 60.9% and 37.6%, respectively. Investigations of the mitochondrial permeability transition pore by patch-clamp techniques revealed for the first time a dose-dependent reduction of the open probability by minocycline (IC(50)=190 nM). Additionally, we provide evidence for the high antioxidant potential of MC in our model. In conclusion, the present data substantiate the beneficial properties of minocycline as promising neuroprotectant by its inhibitory activity on the mitochondrial permeability transition pore.

Minocycline suppresses morphine-induced respiratory depression, suppresses morphine-induced reward, and enhances systemic morphine-induced analgesia

Recent data suggest that opioids can activate immune-like cells of the central nervous system (glia). This opioid-induced glial activation is associated with decreased analgesia, owing to the release of proinflammatory mediators. Here, we examine in rats whether the putative microglial inhibitor, minocycline, may affect morphine-induced respiratory depression and/or morphine-induced reward (conditioned place preference). Systemic co-administration of minocycline significantly attenuated morphine-induced reductions in tidal volume, minute volume, inspiratory force, and expiratory force, but did not affect morphine-induced reductions in respiratory rate. Minocycline attenuation of respiratory depression was also paralleled with significant attenuation by minocycline of morphine-induced reductions in blood oxygen saturation. Minocycline also attenuated morphine conditioned place preference. Minocycline did not simply reduce all actions of morphine, as morphine analgesia was significantly potentiated by minocycline co-administration. Lastly, morphine dose-dependently increased cyclooxygenase-1 gene expression in a rat microglial cell line, an effect that was dose-dependently blocked by minocycline. Together, these data support that morphine can directly activate microglia in a minocycline-suppressible manner and suggest a pivotal role for minocycline-sensitive processes in the mechanisms of morphine-induced respiration depression, reward, and pain modulation.

Minocycline and neurodegenerative diseases

Minocycline is a semi-synthetic, second-generation tetracycline analog which is effectively crossing the blood-brain barrier, effective against gram-positive and -negative infections. In addition to its own antimicrobacterial properties, minocycline has been reported to exert neuroprotective effects over various experimental models such as cerebral ischemia, traumatic brain injury, amyotrophic lateral sclerosis, Parkinson's disease, kainic acid treatment, Huntington' disease and multiple sclerosis. Minocycline has been focused as a neuroprotective agent over neurodegenerative disease since it has been first reported that minocycline has neuroprotective effects in animal models of ischemic injury [Yrjanheikki J, Keinanen R, Pellikka M, Hokfelt T, Koisinaho J. Tetracyclines inhibit microglial activation and are neuroprotective in global brain ischemia. Proc Natl Acad Sci USA 1998;95:15769-74; Yrjanheikki J, Tikka T, Keinanen R, Goldsteins G, Chan PH, Koistinaho J. A tetracycline derivative, minocycline, reduces inflammation and protects against focal cerebral ischemia with a wide therapeutic window. Proc Natl Acad Sci USA 1999;96:13496-500]. Recently, the effect of minocycline on Alzheimer's disease has been also reported. Although its precise primary target is not clear, the action mechanisms of minocycline for neuroprotection reported so far are; via; the inhibition of mitochondrial permeability-transition mediated cytochrome c release from mitochondria, the inhibition of caspase-1 and -3 expressions, and the suppression of microglial activation, involvement in some signaling pathways, metalloprotease activity inhibition. Because of the high tolerance and the excellent penetration into the brain, minocycline has been clinically tried for some neurodegenerative diseases such as stroke, multiple sclerosis, spinal cord injury, amyotropic lateral sclerosis, Hungtington's disease and Parkinson's disease. This review will briefly summarize the effects and action mechanisms of minocycline on neurodegenerative diseases.

Minocycline increases phosphorylation and membrane insertion of neuronal GluR1 receptors

The tetracycline antibiotic minocycline beneficially affects neuronal functioning and also inhibits the enzyme 5-lipoxygenase (5-LOX). We hypothesized that similar to 5-LOX inhibitors, minocycline may increase phosphorylation and membrane insertion of the glutamate receptor GluR1. The experiments were performed in primary cultures of mouse striatal neurons and in the prefrontal cortex and striatum of minocycline-treated mice. In vitro, low micromolar minocycline concentrations increased GluR1 phosphorylation at Ser845 and Ser831 and increased the surface content of GluR1. Minocycline also increased GluR1 phosphorylation in vivo. Increased GluR1 phosphorylation and minocycline treatment have been associated with antidepressant and memory-enhancing activities. Direct consequences of minocycline-increased GluR1 phosphorylation are yet to be established.

Nanotechnology, nanotoxicology, and neuroscience

Nanotechnology, which deals with features as small as a 1 billionth of a meter, began to enter into mainstream physical sciences and engineering some 20 years ago. Recent applications of nanoscience include the use of nanoscale materials in electronics, catalysis, and biomedical research. Among these applications, strong interest has been shown to biological processes such as blood coagulation control and multimodal bioimaging, which has brought about a new and exciting research field called nanobiotechnology. Biotechnology, which itself also dates back approximately 30 years, involves the manipulation of macroscopic biological systems such as cells and mice in order to understand why and how molecular level mechanisms affect specific biological functions, e.g., the role of APP (amyloid precursor protein) in Alzheimer's disease (AD). This review aims (1) to introduce key concepts and materials from nanotechnology to a non-physical sciences community; (2) to introduce several state-of-the-art examples of current nanotechnology that were either constructed for use in biological systems or that can, in time, be utilized for biomedical research; (3) to provide recent excerpts in nanotoxicology and multifunctional nanoparticle systems (MFNPSs); and (4) to propose areas in neuroscience that may benefit from research at the interface of neurobiologically important systems and nanostructured materials.

Therapeutics for neonatal brain injury

Neonatal brain injury is an important cause of death and neurodevelopmental delay. Multiple pathways of oxidant stress, inflammation, and excitotoxicity lead to both early and late phases of cell damage and death. Therapies targeting these different pathways have shown potential in protecting the brain from ongoing injury. More recent therapies, such as growth factors, have demonstrated an ability to increase cell proliferation and repair over longer periods of time. Even though hypothermia, which decreases cerebral metabolism and possibly affects other mechanisms, may show some benefit in particular cases, no widely effective therapeutic interventions for human neonates exist. In this review, we summarize recent findings in neuroprotection and neurogenesis for the immature brain, including combination therapy to optimize repair.

Improvement by minocycline of methamphetamine-induced impairment of recognition memory in mice

INTRODUCTION

Cognitive deficits are a core feature of patients with schizophrenia and methamphetamine (METH) psychosis. We have recently found that repeated METH treatment (1 mg/kg, s.c.) in mice, which induces behavioral sensitization, impairs long-term recognition memory in a novel object recognition test (NORT) and that the impairment is ameliorated by clozapine, but not haloperidol. Recent studies indicate that minocycline, a second-generation tetracycline, has potent neuroprotective effects in various animal models of neurological diseases.

OBJECTIVES

In the present study, we investigated the effect of minocycline on learning and memory in the NORT and behavioral sensitization in mice that had been administered METH for 7 days.

RESULTS

When minocycline (20-40 mg/kg) was administered intraperitoneally once a day for seven consecutive days to mice that had previously been treated with METH for 7 days, it ameliorated the METH-induced impairment of recognition memory in a dose-dependent manner, although the same treatment with minocycline had no effect on behavioral sensitization to METH. The administration of minocycline, together with METH, inhibited the development of METH-induced behavioral sensitization. The improvement in memory caused by minocycline was associated with an amelioration of the novelty-induced activation of extracellular signal-regulated kinase 1/2 in the prefrontal cortex of METH-treated mice.

CONCLUSIONS

These results suggest that minocycline is useful for the treatment of cognitive deficits in patients with METH psychosis or schizophrenia.