Neuroprotective effects of tetracyclines: molecular targets, animal models and human disease

Association between doxycycline use and long-term functioning in patients with schizophrenia

IMPORTANCE AND OBJECTIVE

The brain-penetrant tetracycline antibiotics, minocycline and doxycycline, have been proposed as potential candidate drugs for treatment of schizophrenia, based on preclinical studies and clinical trials. A potential long-term beneficial effect of these antibiotics for schizophrenia patients has not been investigated. This study was designed to determine if redemption of doxycycline prescription in schizophrenia is associated with decreased incidence of disability pension, a proxy for long-term functioning.

DESIGN

We performed a population-based cohort study with data from schizophrenia patients available through the Danish registers. Survival analysis models with time-varying covariates were constructed to assess incidence rate ratios (IRR) of disability pension after exposure to doxycycline or a non-brain penetrant tetracycline, defined as at least one filled prescription. The analysis was adjusted for age, sex, calendar year, parental psychiatric status and educational level.

RESULTS

We used data from 11,157 individuals with schizophrenia (4,945 female and 6,212 male; average age 22.4 years old, standard deviation (std) 4.50). 718 of these were exposed to brain-penetrant doxycycline, and 1,498 individuals redeemed a prescription of one or more of the non-brain-penetrant tetracyclines. The average years at risk per person in this cohort was 4.9, and 2,901 individuals received disability pension in the follow-up period. There was a significantly lower incidence rate of disability pension in schizophrenia patients who had redeemed doxycycline compared to patients who did not redeem a prescription of any tetracycline antibiotics (Incidence rate ratio (IRR) 0.68; 95 % CI 0.56, 0.83). There was also a significant lower rate of disability pension in schizophrenia patients who redeemed doxycycline compared to individuals who redeemed a prescription of one of the non-brain penetrant tetracycline antibiotics (IRR 0.69 95 % CI 0.55, 0.87).

CONCLUSIONS

In this observational study, doxycycline exposure is associated with a reduced incidence of disability pension. These data support further studies on the potential long term neuroprotective effects of doxycycline and level of functioning in schizophrenia patients.

A Sex-Dependent Association Between Doxycycline Use and Development of Schizophrenia

BACKGROUND

Doxycycline and minocycline are brain-penetrant tetracycline antibiotics, which recently gained interest because of their immunomodulatory and neuroprotective properties. Observational studies have suggested that exposure to these drugs may decrease the risk to develop schizophrenia, but results are inconsistent. The aim of this study was to investigate the potential association between doxycycline use and later onset of schizophrenia.

DESIGN

We used data from 1 647 298 individuals born between 1980 and 2006 available through Danish population registers. 79 078 of those individuals were exposed to doxycycline, defined as redemption of at least 1 prescription. Survival analysis models stratified for sex with time-varying covariates were constructed to assess incidence rate ratios (IRRs) for schizophrenia (ICD-10 code F20.xx), with adjustment for age, calendar year, parental psychiatric status, and educational level.

RESULTS

In the non-stratified analysis, there was no association between doxycycline exposure and schizophrenia risk. However, men who redeemed doxycycline had a significantly lower incidence rate for schizophrenia onset compared to men that did not (IRR 0.70; 95% CI 0.57-0.86). By contrast, women had a significantly higher incidence rate for schizophrenia onset, compared to women that did not redeem doxycycline prescriptions (IRR 1.23; 95% CI 1.08, 1.40). The effects were not found for other tetracycline antibiotics (IRR 1.00; 95% CI 0.91, 1.09).

CONCLUSIONS

Doxycycline exposure is associated with a sex-dependent effect on schizophrenia risk. The next steps are replication of the results in independent well-characterized population cohorts, as well as preclinical studies to investigate sex-specific effects of doxycycline on biological mechanisms implicated in schizophrenia.

Doxycycline attenuates l-DOPA-induced dyskinesia through an anti-inflammatory effect in a hemiparkinsonian mouse model

The pharmacological manipulation of neuroinflammation appears to be a promising strategy to alleviate l-DOPA-induced dyskinesia (LID) in Parkinson's disease (PD). Doxycycline (Doxy), a semisynthetic brain-penetrant tetracycline antibiotic having interesting anti-inflammatory properties, we addressed the possibility that this compound could resolve LID in l-DOPA-treated C57BL/6 mice presenting either moderate or intermediate lesions of the mesostriatal dopaminergic pathway generated by intrastriatal injections of 6-OHDA. Doxy, when given subcutaneously before l-DOPA at doses of 20 mg kg^-1 and 40 mg kg^-1, led to significant LID reduction in mice with moderate and intermediate dopaminergic lesions, respectively. Importantly, Doxy did not reduce locomotor activity improved by l-DOPA. To address the molecular mechanism of Doxy, we sacrificed mice with mild lesions 1) to perform the immunodetection of tyrosine hydroxylase (TH) and Fos-B and 2) to evaluate a panel of inflammation markers in the striatum, such as cyclooxygenase-2 and its downstream product Prostaglandin E2 along with the cytokines TNF-α, IL-1β and IL-6. TH-immunodetection revealed that vehicle and Doxy-treated mice had similar striatal lesions, excluding that LID improvement by Doxy could result from neurorestorative effects. Importantly, LID inhibition by Doxy was associated with decreased Fos-B and COX-2 expression and reduced levels of PGE₂, TNF-α, and IL-1β in the dorsolateral striatum of dyskinetic mice. We conclude 1) that Doxy has the potential to prevent LID regardless of the intensity of dopaminergic lesioning and 2) that the anti-inflammatory effects of Doxy probably account for LID attenuation. Overall, the present results further indicate that Doxy might represent an attractive and alternative treatment for LID in PD.

The Outcome of Neurorehabilitation Efficacy and Management of Traumatic Brain Injury

For public health professionals, traumatic brain injury (TBI) and its possible protracted repercussions are a significant source of worry. In opposed to patient neurorehabilitation with developed brain abnormalities of different etiologies, neurorehabilitation of affected persons has several distinct features. The clinical repercussions of the various types of TBI injuries will be discussed in detail in this paper. During severe TBI, the medical course frequently follows a familiar first sequence of coma, accompanied by disordered awareness, followed by agitation and forgetfulness, followed by return of function. Clinicians must be aware of common medical issues that might occur throughout the various stages of neurorehabilitation, for example, posttraumatic hydrocephalus, paroxysmal sympathetic hyperactivity and posttraumatic neuroendocrine disorders, at each step of the process. Furthermore, we address problems about the scheduling of various rehabilitation programs as well as the availability of current data for comprehensive rehabilitative neuropsychology techniques.

Challenges of repurposing tetracyclines for the treatment of Alzheimer's and Parkinson's disease

The novel antibiotic-exploiting strategy in the treatment of Alzheimer's (AD) and Parkinson's (PD) disease has emerged as a potential breakthrough in the field. The research in animal AD/PD models provided evidence on the antiamyloidogenic, anti-inflammatory, antioxidant and antiapoptotic activity of tetracyclines, associated with cognitive improvement. The neuroprotective effects of minocycline and doxycycline in animals initiated investigation of their clinical efficacy in AD and PD patients which led to inconclusive results and additionally to insufficient safety data on a long-standing doxycycline and minocycline therapy in these patient populations. The safety issues should be considered in two levels; in AD/PD patients (particularly antibiotic-induced alteration of gut microbiota and its consequences), and as a world-wide threat of development of bacterial resistance to these antibiotics posed by a fact that AD and PD are widespread incurable diseases which require daily administered long-lasting antibiotic therapy. Recently proposed subantimicrobial doxycycline doses should be thoroughly explored for their effectiveness and long-term safety especially in AD/PD populations. Keeping in mind the antibacterial activity-related far-reaching undesirable effects both for the patients and globally, further work on repurposing these drugs for a long-standing therapy of AD/PD should consider the chemically modified tetracycline compounds tailored to lack antimicrobial but retain (or introduce) other activities effective against the AD/PD pathology. This strategy might reduce the risk of long-term therapy-related adverse effects (particularly gut-related ones) and development of bacterial resistance toward the tetracycline antibiotic agents but the therapeutic potential and desirable safety profile of such compounds in AD/PD patients need to be confirmed.

Bifunctional conducting polymer matrices with antibacterial and neuroprotective effects

Current trends in the field of neural tissue engineering include the design of advanced biomaterials combining excellent electrochemical performance with versatile biological characteristics. The purpose of this work was to develop an antibacterial and neuroprotective coating based on a conducting polymer - poly(3,4-ethylenedioxypyrrole) (PEDOP), loaded with an antibiotic agent - tetracycline (Tc). Employing an electrochemical technique to immobilize Tc within a growing polymer matrix allowed to fabricate robust PEDOP/Tc coatings with a high charge storage capacity (63.65 ± 6.05 mC/cm²), drug release efficiency (629.4 µg/cm² ± 62.7 µg/cm²), and low charge transfer resistance (2.4 ± 0.1 kΩ), able to deliver a stable electrical signal. PEDOP/Tc were found to exhibit strong antimicrobial effects against Gram-negative bacteria Escherichia coli, expressed through negligible adhesion, reduction in viability, and a characteristic elongation of bacterial cells. Cytocompatibility and neuroprotective effects were evaluated using a rat neuroblastoma B35 cell line, and were analyzed using MTT, cell cycle, and Annexin-V apoptosis assays. The presence of Tc was found to enhance neural cell viability and neurite outgrowth. The results confirmed that PEDOP/Tc can serve as an efficient neural electrode coating able to enhance charge transfer, as well as to exhibit bifunctional biological characteristics, different for eukaryotic and prokaryotic cells.

Early Antibiotic Administration is Independently Associated with Improved Survival in Traumatic Brain Injury

BACKGROUND

Central and systemic immune dysfunction after traumatic brain injury (TBI) can lead to infectious-related complications, which may result in delayed mortality. The role of early empiric antibiotics after TBI has not been characterized to date, but is recommended in select cases to decrease complications. We aimed to determine the relationship between early antibiotic use and in-hospital mortality in TBI patients.

METHODS

A retrospective review was conducted of TBI patients requiring ICU admission at an urban, academic, Level I trauma center from 01/2014 to 08/2016. Data collection included demographics, injury characteristics, details regarding antibiotic use, and outcomes. Early antibiotic administration was defined as any antibiotic given within 48 hs from admission. Patients given early antibiotics (EARLY) were compared to those who received their first dose later or did not receive any antibiotics (non-EARLY).

RESULTS

Of the 488 TBI patients meeting inclusion criteria, 189 (38.7%) received early antibiotics. EARLY patients were younger (EARLY 54.2 versus non-EARLY 61.5 ys, P <0.01) and more likely to be male (71.4% versus 60.9%, P = 0.02). Injury severity scores (23.6 versus 17.2, P <0.01) and regional head abbreviated injury scale scores (3.9 versus 3.7, P <0.01) were significantly higher in patients who received early antibiotics. Unadjusted in-hospital mortality rates were similar, however EARLY was associated with a lower mortality rate (AOR 0.17, 95% CI: 0.07 - 0.43, adjusted P <0.01) after adjusting for confounders.

CONCLUSIONS

Despite presenting with a higher injury burden, TBI patients who received early antibiotics had a lower associated mortality rate compared to their counterparts. Future investigations are necessary to understand the underlying mechanisms that result in this potential survival benefit.

The Chemically-Modified Tetracycline COL-3 and Its Parent Compound Doxycycline Prevent Microglial Inflammatory Responses by Reducing Glucose-Mediated Oxidative Stress

We used mouse microglial cells in culture activated by lipopolysaccharide (LPS) or α-synuclein amyloid aggregates (αSa) to study the anti-inflammatory effects of COL-3, a tetracycline derivative without antimicrobial activity. Under LPS or αSa stimulation, COL-3 (10, 20 µM) efficiently repressed the induction of the microglial activation marker protein Iba-1 and the stimulated-release of the pro-inflammatory cytokine TNF-α. COL-3′s inhibitory effects on TNF-α were reproduced by the tetracycline antibiotic doxycycline (DOX; 50 µM), the glucocorticoid dexamethasone, and apocynin (APO), an inhibitor of the superoxide-producing enzyme NADPH oxidase. This last observation suggested that COL-3 and DOX might also operate themselves by restraining oxidative stress-mediated signaling events. Quantitative measurement of intracellular reactive oxygen species (ROS) levels revealed that COL-3 and DOX were indeed as effective as APO in reducing oxidative stress and TNF-α release in activated microglia. ROS inhibition with COL-3 or DOX occurred together with a reduction of microglial glucose accumulation and NADPH synthesis. This suggested that COL-3 and DOX might reduce microglial oxidative burst activity by limiting the glucose-dependent synthesis of NADPH, the requisite substrate for NADPH oxidase. Coherent with this possibility, the glycolysis inhibitor 2-deoxy-D-glucose reproduced the immunosuppressive action of COL-3 and DOX in activated microglia. Overall, we propose that COL-3 and its parent compound DOX exert anti-inflammatory effects in microglial cells by inhibiting glucose-dependent ROS production. These effects might be strengthened by the intrinsic antioxidant properties of DOX and COL-3 in a self-reinforcing manner.

Minocycline Treatment Reduces Mass and Force Output From Fast-Twitch Mouse Muscles and Inhibits Myosin Production in C2C12 Myotubes

Minocycline, a tetracycline-class of antibiotic, has been tested with mixed effectiveness on neuromuscular disorders such as amyotrophic lateral sclerosis, autoimmune neuritis and muscular dystrophy. The independent effect of minocycline on skeletal muscle force production and signalling remain poorly understood. Our aim here is to investigate the effects of minocycline on muscle mass, force production, myosin heavy chain abundance and protein synthesis. Mice were injected with minocycline (40 mg/kg i.p.) daily for 5 days and sacrificed at day six. Fast-twitch EDL, TA muscles and slow-twitch soleus muscles were dissected out, the TA muscle was snap-frozen and the remaining muscles were attached to force transducer whilst maintained in an organ bath. In C2C12 myotubes, minocycline was applied to the media at a final concentration of 10 μg/mL for 48 h. In minocycline treated mice absolute maximal force was lower in fast-twitch EDL while in slow-twitch soleus there was an increase in the time to peak and relaxation of the twitch. There was no effect of minocycline treatment on the other contractile parameters measured in isolated fast- and slow-twitch muscles. In C2C12 cultured cells, minocycline treatment significantly reduced both myosin heavy chain content and protein synthesis without visible changes to myotube morphology. In the TA muscle there was no significant changes in myosin heavy chain content. These results indicate that high dose minocycline treatment can cause a reduction in maximal isometric force production and mass in fast-twitch EDL and impair protein synthesis during myogenesis in C2C12 cultured cells. These findings have important implications for future studies investigating the efficacy of minocycline treatment in neuromuscular or other muscle-atrophy inducing conditions.

Modulation of Huntington's disease in Drosophila

Huntington's disease (HD) is a progressive neurodegenerative disorder which deteriorates the physical and mental abilities of the patients. It is an autosomal dominant disorder and is mainly caused by the expansion of a repeating CAG triplet. A number of animal models ranging from worms, fruit flies, mice and rats to pigs, sheep and monkeys are available which have been helpful in understanding various pathways involved during the progression of the disease. Drosophila is one of the most commonly used model organisms for biomedical science, due to low cost maintenance, short life span and easily implications of genetic tools. The present review provides brief description of HD and the studies carried out for HD to date taking Drosophila as a model.

CMT-3 targets different α-synuclein aggregates mitigating their toxic and inflammogenic effects

Parkinson's disease (PD) is a neurodegenerative disorder for which only symptomatic treatments are available. Repurposing drugs that target α-synuclein aggregation, considered one of the main drivers of PD progression, could accelerate the development of disease-modifying therapies. In this work, we focused on chemically modified tetracycline 3 (CMT-3), a derivative with reduced antibiotic activity that crosses the blood–brain barrier and is pharmacologically safe. We found that CMT-3 inhibited α-synuclein amyloid aggregation and led to the formation of non-toxic molecular species, unlike minocycline. Furthermore, CMT-3 disassembled preformed α-synuclein amyloid fibrils into smaller fragments that were unable to seed in subsequent aggregation reactions. Most interestingly, disaggregated species were non-toxic and less inflammogenic on brain microglial cells. Finally, we modelled the interactions between CMT-3 and α-synuclein aggregates by molecular simulations. In this way, we propose a mechanism for fibril disassembly. Our results place CMT-3 as a potential disease modifier for PD and possibly other synucleinopathies.

Antibiotics with therapeutic effects on spinal cord injury: a review

Accumulating evidence indicates that a considerable number of antibiotics exert anti-inflammatory and neuroprotective effects in different central and peripheral nervous system diseases including spinal cord injury (SCI). Both clinical and preclinical studies on SCI have found therapeutic effects of antibiotics from different families on SCI. These include macrolides, minocycline, β-lactams, and dapsone, all of which have been found to improve SCI sequels and complications. These antibiotics may target similar signaling pathways such as reducing inflammatory microglial activity, promoting autophagy, inhibiting neuronal apoptosis, and modulating the SCI-related mitochondrial dysfunction. In this review paper, we will discuss the mechanisms underlying therapeutic effects of these antibiotics on SCI, which not only could supply vital information for investigators but also guide clinicians to consider administering these antibiotics as part of a multimodal therapeutic approach for management of SCI and its complications.

Management of Traumatic Brain Injury: From Present to Future

TBI (traumatic brain injury) is a major cause of death among youth in industrialized societies. Brain damage following traumatic injury is a result of direct and indirect mechanisms; indirect or secondary injury involves the initiation of an acute inflammatory response, including the breakdown of the blood–brain barrier (BBB), brain edema, infiltration of peripheral blood cells, and activation of resident immunocompetent cells, as well as the release of numerous immune mediators such as interleukins and chemotactic factors. TBI can cause changes in molecular signaling and cellular functions and structures, in addition to tissue damage, such as hemorrhage, diffuse axonal damages, and contusions. TBI typically disturbs brain functions such as executive actions, cognitive grade, attention, memory data processing, and language abilities. Animal models have been developed to reproduce the different features of human TBI, better understand its pathophysiology, and discover potential new treatments. For many years, the first approach to manage TBI has been treatment of the injured tissue with interventions designed to reduce the complex secondary-injury cascade. Several studies in the literature have stressed the importance of more closely examining injuries, including endothelial, microglia, astroglia, oligodendroglia, and precursor cells. Significant effort has been invested in developing neuroprotective agents. The aim of this work is to review TBI pathophysiology and existing and potential new therapeutic strategies in the management of inflammatory events and behavioral deficits associated with TBI.

Molecular targets in cerebral malaria for developing novel therapeutic strategies

Cerebral malaria (CM) is the severe neurological complication associated with Plasmodium falciparum infection. In clinical settings CM is predominantly characterized by fever, epileptic seizures, and asexual forms of parasite on blood smears, coma and even death. Cognitive impairment in the children and adults even after survival is one of the striking consequences of CM. Poor diagnosis often leads to inappropriate malaria therapy which in turn progress into a severe form of disease. Activation of multiple cell death pathways such as Inflammation, oxidative stress, apoptosis and disruption of blood brain barrier (BBB) plays critical role in the pathogenesis of CM and secondary brain damage. Thus, understanding such mechanisms of neuronal cell death might help to identify potential molecular targets for CM. Mitigation strategies for mortality rate and long-term cognitive deficits caused by existing anti-malarial drugs still remains a valid research question to ask. In this review, we discuss in detail about critical neuronal cell death mechanisms and the overall significance of adjunctive therapy with recent trends, which provides better insight towards establishing newer therapeutic strategies for CM.

Minocycline Preserves the Integrity and Permeability of BBB by Altering the Activity of DKK1-Wnt Signaling in ICH Model

Disruption of the blood-brain barrier (BBB) and subsequent neurological deficits are the most severe consequence of intracerebral hemorrhage (ICH). Minocycline has been wildly used clinically as a neurological protective agent in clinical practice. However, the underlying mechanisms by which minocycline functions remain unclear. Therefore, we assessed the influence of minocycline on BBB structure, neurological function, and inflammatory responses in a collagenase-induced ICH model, and elucidated underlying molecular mechanisms as well. Following a single injection of collagenase VII-S into the basal ganglia, BBB integrity was assessed by Evans blue extravasation while neurological function was assessed using an established neurologic function scoring system. Minocycline treatment significantly alleviated the severity of BBB disruption, brain edema, and neurological deficits in ICH model. Moreover, minocycline decreased the production of inflammatory mediators including TNF, IL-6, and MMP-9, by microglia. Minocycline treatment decreased DKK1 expression but increased Wnt1, β-catenin and Occludin, a phenomenon mimicked by DKK1 silencing. These data suggest that minocycline improves the consequences of ICH by preserving BBB integrity and attenuating neurologic deficits in a DKK1-related manner that involves enhancement of the Wnt1-β-catenin activity.

Oxytetracycline does not cause growth promotion in finfish

Until recently, use of antibiotics to enhance terrestrial animal growth performance was a common, U.S. Food and Drug Administration (FDA)-approved, but controversial practice. There are no FDA-approved production claims for antibiotic drug use in fish, but it is a common misconception that antibiotics are widely used for this purpose in U.S. aquaculture. Antibiotics are not thought to be effective growth promoters in fish, but there is little quantitative data available to address whether there are growth-promoting effects that might incentivize the use of antibiotics in this way, despite legal prohibitions. Therefore, this study was conducted to determine if oral administration of oxytetracycline, an antibiotic with known growth-promoting effects in terrestrial livestock, has a similar effect when applied to channel catfish Ictalurus punctatus, hybrid striped bass Morone chrysops × M. saxatilis, Nile tilapia Oreochromis niloticus, or rainbow trout Oncorhynchus mykiss. Oxytetracycline products with production claims are typically applied at doses substantially lower than the approved therapeutic doses for the same products. Medication (0, 0.24, or 1.2 g oxytetracycline dihydrate kg-1 feed) and feeding rates (3% BW d-1) were selected to achieve target daily doses of 0, 16, or 80 mg kg-1 fish representing control, subtherapeutic, and therapeutic treatments. Replicate groups of fish (N = 4) were fed accordingly for 8 wk. Overall, oral administration of oxytetracycline did not affect survival or promote growth of the selected taxa, with no significant differences observed for weight gain, feed conversion ratio, or specific growth rate (P > 0.05 in all cases). Few differences were observed in organosomatic indices and in the frequency of tissue abnormalities; where present, these differences tended to suggest a negative effect of long-term dietary exposure to oxytetracycline. These data demonstrate that there is no benefit to dietary supplementation with oxytetracycline for nontherapeutic purposes in a range of economically important finfish species. As such, our results indicate there is little incentive to misuse oxytetracycline products for purposes of growth promotion in U.S. aquaculture.

Microglia Play an Active Role in Obesity-Associated Cognitive Decline

Obesity affects >600 million people worldwide, a staggering number that appears to be on the rise. One of the lesser known consequences of obesity is its deleterious effects on cognition, which have been well documented across many cognitive domains and age groups. To investigate the cellular mechanisms that underlie obesity-associated cognitive decline, we used diet-induced obesity in male mice and found memory impairments along with reductions in dendritic spines, sites of excitatory synapses, increases in the activation of microglia, the brain's resident immune cells, and increases in synaptic profiles within microglia, in the hippocampus, a brain region linked to cognition. We found that partial knockdown of the receptor for fractalkine, a chemokine that can serve as a "find me" cue for microglia, prevented microglial activation and cognitive decline induced by obesity. Furthermore, we found that pharmacological inhibition of microglial activation in obese mice was associated with prevention of both dendritic spine loss and cognitive degradation. Finally, we observed that pharmacological blockade of microglial phagocytosis lessened obesity-associated cognitive decline. These findings suggest that microglia play an active role in obesity-associated cognitive decline by phagocytosis of synapses that are important for optimal function.SIGNIFICANCE STATEMENT Obesity in humans correlates with reduced cognitive function. To investigate the cellular mechanisms underlying this, we used diet-induced obesity in mice and found impaired performance on cognitive tests of hippocampal function. These deficits were accompanied by reduced numbers of dendritic spines, increased microglial activation, and increased synaptic profiles within microglia. Inhibition of microglial activation by transgenic and pharmacological methods prevented cognitive decline and dendritic spine loss in obese mice. Moreover, pharmacological inhibition of the phagocytic activity of microglia was also sufficient to prevent cognitive degradation. This work suggests that microglia may be responsible for obesity-associated cognitive decline and dendritic spine loss.

Inflammation in CNS neurodegenerative diseases

Neurodegenerative diseases, the leading cause of morbidity and disability, are gaining increased attention as they impose a considerable socioeconomic impact, due in part to the ageing community. Neuronal damage is a pathological hallmark of Alzheimer's and Parkinson's diseases, amyotrophic lateral sclerosis, Huntington's disease, spinocerebellar ataxia and multiple sclerosis, although such damage is also observed following neurotropic viral infections, stroke, genetic white matter diseases and paraneoplastic disorders. Despite the different aetiologies, for example, infections, genetic mutations, trauma and protein aggregations, neuronal damage is frequently associated with chronic activation of an innate immune response in the CNS. The growing awareness that the immune system is inextricably involved in shaping the brain during development as well as mediating damage, but also regeneration and repair, has stimulated therapeutic approaches to modulate the immune system in neurodegenerative diseases. Here, we review the current understanding of how astrocytes and microglia, as well as neurons and oligodendrocytes, shape the neuroimmune response during development, and how aberrant responses that arise due to genetic or environmental triggers may predispose the CNS to neurodegenerative diseases. We discuss the known interactions between the peripheral immune system and the brain, and review the current concepts on how immune cells enter and leave the CNS. A better understanding of neuroimmune interactions during development and disease will be key to further manipulating these responses and the development of effective therapies to improve quality of life, and reduce the impact of neuroinflammatory and degenerative diseases.

Involvement of Neuroinflammation in the Pathogenesis of Monocrotaline-Induced Pulmonary Hypertension

Pulmonary hypertension (PH) is a devastating disease and its successful treatment remains to be accomplished despite recent advances in pharmacotherapy. It has been proposed that PH be considered as a systemic disease, rather than primarily a disease of the pulmonary vasculature. Consequently, an investigation of the intricate interplay between multiple organs such as brain, vasculature, and lung in PH could lead to the identification of new targets for its therapy. However, little is known about this interplay. This study was undertaken to examine the concept that altered autonomic-pulmonary communication is important in PH pathophysiology. Therefore, we hypothesize that activation of microglial cells in the paraventricular nucleus of hypothalamus and neuroinflammation is associated with increased sympathetic drive and pulmonary pathophysiology contributing to PH. We utilized the monocrotaline rat model for PH and intracerebroventricular administration of minocycline for inhibition of microglial cells activation to investigate this hypothesis. Hemodynamic, echocardiographic, histological, immunohistochemical, and confocal microscopic techniques assessed cardiac and pulmonary function and microglial cells. Monocrotaline treatment caused cardiac and pulmonary pathophysiology associated with PH. There were also increased activated microglial cells and mRNA for proinflammatory cytokines (IL [interleukin]-1β, IL-6, and TNF [tumor necrosis factor]-α) in the paraventricular nucleus. Furthermore, increased sympathetic drive and plasma norepinephrine were observed in rats with PH. Intracerebroventricular infusion of minocycline inhibited all these parameters and significantly attenuated PH. These observations implicate a dysfunctional autonomic-lung communication in the development and progression of PH providing new therapeutic targets, such as neuroinflammation, for PH therapy.

Antineuroinflammation of Minocycline in Stroke

Accumulating research substantiates the statement that inflammation plays an important role in the development of stroke. Both proinflammatory and anti-inflammatory mediators are involved in the pathogenesis of stroke, an imbalance of which leads to inflammation. Anti-inflammation is a kind of hopeful strategy for the prevention and treatment of stroke. Substantial studies have demonstrated that minocycline, a second-generation semisynthetic antibiotic belonging to the tetracycline family, can inhibit neuroinflammation, inflammatory mediators and microglia activation, and improve neurological outcome. Experimental and clinical data have found the preclinical and clinical potential of minocycline in the treatment of stroke due to its anti-inflammation properties and anti-inflammation-induced pathogeneses, including antioxidative stress, antiapoptosis, inhibiting leukocyte migration and microglial activation, and decreasing matrix metalloproteinases activity. Hence, it suggests a great future for minocycline in the therapeutics of stroke that diminish the inflammatory progress of stroke.

Minocycline protects developing brain against ethanol-induced damage

Fetal alcohol spectrum disorders (FASD) are caused by ethanol exposure during the pregnancy and is the leading cause of mental retardation. Ethanol exposure during the development results in the loss of neurons in the developing brain, which may underlie many neurobehavioral deficits associated with FASD. It is important to understand the mechanisms underlying ethanol-induced neuronal loss and develop appropriate therapeutic strategies. One of the potential mechanisms involves neuroimmune activation. Using a third trimester equivalent mouse model of ethanol exposure, we demonstrated that ethanol induced a wide-spread neuroapoptosis, microglial activation, and neuroinflammation in C57BL/6 mice. Minocycline is an antibiotic that inhibits microglial activation and alleviates neuroinflammation. We tested the hypothesis that minocycline may protect neurons ethanol-induced neuron death by inhibiting microglial activation and neuroinflammation. We showed that minocycline significantly inhibited ethanol-induced caspase-3 activation, microglial activation, and the expression of pro-inflammatory cytokines. In contrast, minocycline reversed ethanol inhibition of anti-inflammatory cytokines. Minocycline blocked ethanol-induced activation of GSK3β, a key mediator of neuroinflammation and microglial activation in the developing brain. Consistent with the in vivo observations, minocycline inhibited ethanol-induced the expression of pro-inflammatory cytokines and activation of GSK3β in a microglia cell line (SIM-9). GSK3β inhibitor eliminated ethanol activation of pro-inflammatory cytokines in SIM-9 cells. Co-cultures of cortical neurons and SIM-9 microglia cells sensitized neurons to alcohol-induced neuronal death. Minocycline protected neurons against ethanol-induced neuronal death in neurons/microglia co-cultures. Together, these results suggest that minocycline may ameliorate ethanol neurotoxicity in the developing by alleviating GSK3β-mediated neuroinflammation.

Preventive effects of minocycline in a neurodevelopmental two-hit model with relevance to schizophrenia

Maternal immune activation can increase the vulnerability of the offspring to develop neuroimmune and behavioral abnormalities in response to stress in puberty. In offspring of immune-challenged mothers, stress-induced inflammatory processes precede the adult onset of multiple behavioral dysfunctions. Here, we explored whether an early anti-inflammatory intervention during peripubertal stress exposure might prevent the subsequent emergence of adult behavioral pathology. We used an environmental two-hit model in mice, in which prenatal maternal administration of the viral mimetic poly(I:C) served as the first hit, and exposure to sub-chronic unpredictable stress during peripubertal maturation as the second hit. Using this model, we examined the effectiveness of the tetracycline antibiotic minocycline (MINO) given during stress exposure to block stress-induced inflammatory responses and to prevent subsequent behavioral abnormalities. We found that combined exposure to prenatal immune activation and peripubertal stress caused significant deficits in prepulse inhibition and increased sensitivity to the psychotomimetic drugs amphetamine and dizocilpine in adulthood. MINO treatment during stress exposure prevented the emergence of these behavioral dysfunctions. In addition, the pharmacological intervention blocked hippocampal and prefrontal microglia activation and interleukin-1β expression in offspring exposed to prenatal infection and peripubertal stress. Together, these findings demonstrate that presymptomatic MINO treatment can prevent the subsequent emergence of multiple behavioral abnormalities relevant to human neuropsychiatric disorders with onset in early adulthood, including schizophrenia. Our epidemiologically informed two-hit model may thus encourage attempts to explore the use of anti-inflammatory agents in the early course of brain disorders that are characterized by signs of central nervous system inflammation during development.

Minocycline Effectively Protects the Rabbit's Spinal Cord From Aortic Occlusion-Related Ischemia

OBJECTIVES

To identify the minocycline anti-inflammatory and antiapoptotic mechanisms through which it is believed to exert spinal cord protection during aortic occlusion in the rabbit model.

DESIGN

An animal model of aortic occlusion-related spinal cord ischemia. Randomized study with a control group and pre-ischemia and post-ischemia escalating doses of minocycline to high-dose minocycline in the presence of either hyperglycemia, a pro-apoptotic maneuver, or wortmannin, a specific phosphatidylinositol 3-kinase antagonist.

SETTING

Tertiary medical center and school of medicine laboratory.

PARTICIPANTS

Laboratory animals-rabbits.

INTERVENTIONS

Balloon obstruction of infrarenal aorta introduced via femoral artery incision.

RESULTS

Severe hindlimb paralysis (mean Tarlov score 0.36±0.81 out of 3) was observed in all the control group animals (9 of 11 with paraplegia and 2 of 11 with paraparesis) compared with 11 of 12 neurologically intact animals (mean Tarlov score 2.58±0.90 [p = 0.001 compared with control]) in the high-dose minocycline group. This protective effect was observed partially during a state of hyperglycemia and was completely abrogated by wortmannin. Minocycline administration resulted in higher neurologic scores (p = 0.003) and a shift to viable neurons and more apoptotic-stained nuclei resulting from reduced necrosis (p = 0.001).

CONCLUSIONS

In a rabbit model of infrarenal aortic occlusion, minocycline effectively reduced paraplegia by increasing the number of viable neurons in a dose-dependent manner. Its action was completely abrogated by inhibiting the phosphatidylinositol 3-kinase pathway and was inhibited partially by the pro-apoptotic hyperglycemia maneuver, indicating that the activation of cell salvage pathways and mitochondrial sites are possible targets of minocycline action in an ischemic spinal cord.

Investigational agents for treatment of traumatic brain injury

INTRODUCTION

Traumatic brain injury (TBI) is a major cause of death and disability worldwide. To date, there are no pharmacologic agents proven to improve outcomes from TBI because all the Phase III clinical trials in TBI have failed. Thus, there is a compelling need to develop treatments for TBI.

AREAS COVERED

The following article provides an overview of select cell-based and pharmacological therapies under early development for the treatment of TBI. These therapies seek to enhance cognitive and neurological functional recovery through neuroprotective and neurorestorative strategies.

EXPERT OPINION

TBI elicits both complex degenerative and regenerative tissue responses in the brain. TBI can lead to cognitive, behavioral, and motor deficits. Although numerous promising neuroprotective treatment options have emerged from preclinical studies that mainly target the lesion, translation of preclinical effective neuroprotective drugs to clinical trials has proven challenging. Accumulating evidence indicates that the mammalian brain has a significant, albeit limited, capacity for both structural and functional plasticity, as well as regeneration essential for spontaneous functional recovery after injury. A new therapeutic approach is to stimulate neurovascular remodeling by enhancing angiogenesis, neurogenesis, oligodendrogenesis, and axonal sprouting, which in concert, may improve neurological functional recovery after TBI.

Biotic acts of antibiotics

Biological functions of antibiotics are not limited to killing. The most likely function of antibiotics in natural microbial ecosystems is signaling. Does this signaling function of antibiotics also extend to the eukaryotic – in particular mammalian – cells? In this review, the host modulating properties of three classes of antibiotics (macrolides, tetracyclines, and β-lactams) will be briefly discussed. Antibiotics can be effective in treatment of a broad spectrum of diseases and pathological conditions other than those of infectious etiology and, in this capacity, may find widespread applications beyond the intended antimicrobial use. This use, however, should not compromise the primary function antibiotics are used for. The biological background for this inter-kingdom signaling is also discussed.

Inhibition of microglia activation as a phenotypic assay in early drug discovery

Complex biological processes such as inflammation, cell death, migration, proliferation, and the release of biologically active molecules can be used as outcomes in phenotypic assays during early stages of drug discovery. Although target-based approaches have been widely used over the past decades, a disproportionate number of first-in-class drugs have been identified using phenotypic screening. This review details phenotypic assays based on inhibition of microglial activation and their utility in primary and secondary screening, target validation, and pathway elucidation. The role of microglia, both in normal as well as in pathological conditions such as chronic neurodegenerative diseases, is reviewed. Methodologies to assess microglia activation in vitro are discussed in detail, and classes of therapeutic drugs known to decrease the proinflammatory and cytotoxic responses of activated microglia are appraised, including inhibitors of glutaminase, cystine/glutamate antiporter, nuclear factor κB, and mitogen-activated protein kinases.

Beneficial effects of minocycline and botulinum toxin-induced constraint physical therapy following experimental traumatic brain injury

BACKGROUND

Effective recovery from functional impairments caused by traumatic brain injury (TBI) requires appropriate rehabilitation therapy. Multiple pathways are involved in secondary injury and recovery suggesting a role for multimodal approaches.

OBJECTIVE

Here, we examined the efficacy of the anti-inflammatory agent minocycline and botulinum toxin (botox)-induced limb constraint with structured physical therapy, delivered alone or in combination, after a severe TBI produced by a controlled cortical impact in rats.

METHODS

Minocycline was administered at 25 mg/kg daily for 2 weeks beginning 1 day after TBI or sham surgery. For constraint/physical therapy, botox-type A was injected into the nonaffected forearm muscle 1 day after injury and 2 weeks of physical therapy commenced at 5 days after injury. Functional evaluations were conducted 8 weeks after injury.

RESULTS

Minocycline, either as a monotherapy or as combination treatment with botox/physical therapy significantly reduced impairments of spatial learning and memory in the water maze test, whereas botox/physical therapy reduced forelimb motor asymmetry and improved manual dexterity in the cylinder and vermicelli handling tests, A synergistic effect between the 2 treatments was observed when rats performed tasks requiring dexterity. Inflammation was attenuated in the peri-contusion cortex and hippocampus in all TBI groups receiving mono or combination therapies, though there was no significant difference in lesion size among groups.

CONCLUSION

These data provide a rationale for incorporating anti-inflammatory treatment during rehabilitation therapy.

A pilot open-label trial of minocycline in patients with autism and regressive features

BACKGROUND

Minocycline is a tetracycline derivative that readily crosses the blood brain barrier and appears to have beneficial effects on neuroinflammation, microglial activation and neuroprotection in a variety of neurological disorders. Both microglial activation and neuroinflammation have been reported to be associated with autism. The study was designed to evaluate the effects of minocycline treatment on markers of neuroinflammation and autism symptomatology in children with autism and a history of developmental regression.

METHODS

Eleven children were enrolled in an open-label trial of six months of minocycline (1.4 mg/kg). Ten children completed the trial. Behavioral measures were collected and cerebrospinal fluid (CSF), serum and plasma were obtained before and at the end of minocycline treatment and were analyzed for markers of neuroinflammation.

RESULTS

Clinical improvements were negligible. The laboratory assays demonstrated significant changes in the expression profile of the truncated form of brain derived neurotrophic factor (BDNF) (P = 0.042) and hepatic growth factor (HGF) (P = 0.028) in CSF. In serum, the ratio of the truncated BDNF form and α-2 macroglobulin (α-2 M), was also significantly lower (P = 0.028) while the mature BDNF/α-2 M ratio revealed no difference following treatment. Only the chemokine CXCL8 (IL-8) was significantly different (P = 0.047) in serum while no significant changes were observed in CSF or serum in chemokines such as CCL2 (MCP-1) or cytokines such as TNF-α, CD40L, IL-6, IFN-γ and IL-1β when pre- and post-treatment levels of these proteins were compared. No significant pre- and post-treatment changes were seen in the profiles of plasma metalloproteinases, putative targets of the effects of minocycline.

CONCLUSIONS

Changes in the pre- and post-treatment profiles of BDNF in CSF and blood, HGF in CSF and CXCL8 (IL-8) in serum, suggest that minocycline may have effects in the CNS by modulating the production of neurotrophic growth factors. However, in this small group of children, no clinical improvements were observed during or after the six months of minocycline administration.

TRIAL REGISTRATION

NCT00409747.

Comparative genomics and functional study of lipid metabolic genes in Caenorhabditis elegans

BACKGROUND

Animal models are indispensable to understand the lipid metabolism and lipid metabolic diseases. Over the last decade, the nematode Caenorhabditis elegans has become a popular animal model for exploring the regulation of lipid metabolism, obesity, and obese-related diseases. However, the genomic and functional conservation of lipid metabolism from C. elegans to humans remains unknown. In the present study, we systematically analyzed genes involved in lipid metabolism in the C. elegans genome using comparative genomics.

RESULTS

We built a database containing 471 lipid genes from the C. elegans genome, and then assigned most of lipid genes into 16 different lipid metabolic pathways that were integrated into a network. Over 70% of C. elegans lipid genes have human orthologs, with 237 of 471 C. elegans lipid genes being conserved in humans, mice, rats, and Drosophila, of which 71 genes are specifically related to human metabolic diseases. Moreover, RNA-mediated interference (RNAi) was used to disrupt the expression of 356 of 471 lipid genes with available RNAi clones. We found that 21 genes strongly affect fat storage, development, reproduction, and other visible phenotypes, 6 of which have not previously been implicated in the regulation of fat metabolism and other phenotypes.

CONCLUSIONS

This study provides the first systematic genomic insight into lipid metabolism in C. elegans, supporting the use of C. elegans as an increasingly prominent model in the study of metabolic diseases.

Tetracyclines and neuromuscular disorders

Tetracyclines are a class of antibiotics which could act as neuroprotective molecules in several neurological disorders, such as Huntington disease, Parkinson disease, stroke and multiple sclerosis. The main biological effects of tetracyclines are the inhibition of microglial activation, the attenuation of apoptosis and the suppression of reactive oxygen species production. The anti-apoptotic effect of tetracyclines involves the mitochondrion, and the major target for neuroprotective effects of tetracyclines lies within the complex network that links mitochondria, oxidative stress and apoptosis.

Neuromuscular disorders are due to dysfunction of motor neurons, peripheral nerves, neuromuscular junction, or skeletal muscle itself. Animal studies have shown that minocycline could play neuroprotective effects in amyotrophic lateral sclerosis, but these positive findings have not been replicated in patients. Other neuromuscular disorders which tetracyclines may benefit are Guillain-Barré syndrome and other neuropathies, muscular dystrophies and mitochondrial disorders. However, well-designed double-blind controlled trials are still needed. Further studies are strongly needed to establish the most appropriate timing and dosage, as well as the indications for which tetracyclines could be effective and safe.

Here, we review the neuroprotective effects of tetracyclines in animal models, the clinical studies in humans, and we focus on their potential application in patients with neuromuscular disorders.

What is behind the non-antibiotic properties of minocycline?

Minocycline is a second-generation, semi-synthetic tetracycline that has been in use in therapy for over 30 years for its antibiotic properties against both Gram-positive and Gram-negative bacteria. It displays antibiotic activity due to its ability to bind to the 30S ribosomal subunit of bacteria and thus inhibit protein synthesis. More recently, it has been described to exert a variety of biological actions beyond its antimicrobial activity, including anti-inflammatory and anti-apoptotic activities, inhibition of proteolysis, as well as suppression of angiogenesis and tumor metastasis, which have been confirmed in different experimental models of non-infectious diseases. There are also many studies that have focused on the mechanisms involved in these non-antibiotic properties of minocycline, including anti-oxidant activity, inhibition of several enzyme activities, inhibition of apoptosis and regulation of immune cell activation and proliferation. This review summarizes the current findings in this topic, mainly focusing on the mechanisms underlying the immunomodulatory and anti-inflammatory activities of minocycline.

Tetracycline treatment in patients with progressive external ophthalmoplegia

BACKGROUND

Tetracyclines could have neuroprotective effects in neuromuscular and neurodegenerative disorders. AIMS OF THE STUDY AND METHODS: Objective of this double-blind randomized pilot study (followed by an adjunctive open-label phase) was to evaluate whether tetracycline (500 mg/day × 14 days/month × 3 months) could be useful in patients (n = 16) with progressive external ophthalmoplegia (PEO).

RESULTS

Our results do not formally support any effect of tetracycline on eye motility in PEO. However, some possible protective effects could not be completely ruled out, i.e. a further analysis suggests a possible difference between the tetracycline group and the placebo group, significant at least for oblique motility, when comparing the ratio between the end of the double-blind phase and baseline. Tetracycline could modify some oxidative stress biomarkers in patients with PEO.

CONCLUSIONS

Further studies are needed to confirm such effects of tetracycline in patients with PEO, if any, and to clarify the mechanisms of action for antioxidant effects of tetracyclines in mitochondrial disorders and other diseases.

Minocycline protects SH-SY5Y cells from 6-hydroxydopamine by inhibiting both caspase-dependent and -independent programmed cell death

Minocycline, a tetracyclic antibiotic, exerts both antiinflammation by acting on microglia and a direct protection on neurons by inhibiting the apoptotic machinery at various levels. However, we are not aware of any study investigating the effects of minocycline on caspase-independent programmed cell death (PCD) pathways. This study investigated these alternative pathways in SH-SY5Y cells, a human dopaminergic cell line, challenged with 6-hydroxydopamine (6-OHDA). Minocycline exhibited neuroprotection and inhibition of the toxin-induced caspase-3-like activity, DNA fragmentation, and chromatin condensation, hallmarks of apoptosis. Moreover, we revealed that 6-OHDA also activated caspase-independent PCDs (such as paraptosis), which required de novo protein synthesis. Additionally, by separately monitoring caspase-dependent and caspase-independent pathways, we showed that inhibition of apoptosis only partially explained the protective effect of minocycline. Moreover, we observed that minocycline reduced the protein content of cells but, unexpectedly, increased the protein synthesis. These findings suggest that minocycline may actually increase protein degradation, so it may also accelerate the clearance of aberrant proteins. In conclusion, we report for the first time evidence indicating that minocycline may inhibit PCD pathways that are additional to conventional apoptosis.

Sexual dimorphism in ischemic stroke: lessons from the laboratory

Ischemic stroke is emerging as a major health problem for elderly women. Women have lower stroke incidence than men until an advanced age, when the epidemiology of ischemic stroke shifts and incidence rises dramatically in women. Experimental models of rodent stroke have replicated this clinical epidemiology, with exacerbated injury in older compared with young female rodents. Many of the detrimental effects of aging on ischemic stroke outcome in females can be replicated by ovariectomy, suggesting that hormones such as estrogen play a neuroprotective role. However, emerging data suggest that the molecular mechanisms leading to ischemic cell death differ in the two sexes, and these effects may be independent of circulating hormone levels. This article highlights recent clinical and experimental literature on sex differences in stroke outcomes and mechanisms.

Treating inflammation in childhood neurodegenerative disorders

Inflammation of the central nervous system is a prominent feature in many childhood neurodegenerative conditions, with various studies demonstrating the upregulation of the innate and adaptive immune system. Recent evidence also suggests that this inflammatory process can contribute to further neurodegeneration. Furthermore, immunosuppression in mouse models of a few lysosomal storage disorders has demonstrated that attenuation of this immune response can influence the clinical and neuropathological progression. However, there are significant challenges before this finding translates to patient care. Treating inflammation in neurodegenerative conditions requires the identification of the time point when inflammation becomes pathogenic, after which the safest therapeutic strategies are required to target the various components and confounders of inflammation. Nevertheless, as the progress made towards effective gene-, cellular-, and enzyme-based therapy in most of these disorders has been disappointing, treating pathogenic inflammation may offer the clinician another therapeutic strategy in managing these devastating disorders.

High throughput screening of small molecule libraries for modifiers of radiation responses

PURPOSE

An unbiased approach of drug discovery through high-throughput screening (HTS) of libraries of chemically defined and bioactive small molecule compounds was used to identify modulators of radiation injury with an emphasis on radioprotectors and mitigators rather than radiosensitisers. Assay system endpoints included radiation-induced genotoxicity and DNA damage in yeast and apoptosis in murine lymphocytes. Large-scale data mining of chemically diverse libraries identified agents that were effective with all endpoints. HTS of bioactive compound libraries against murine lymphocytes profiled tetracycline and fluoroquinolone antibiotics and cyclopiazonic acid as having activity, and structure-activity analysis showed a common pharmacophore. Purine nucleosides, the interferon inducer tilorone, and linoleic acid were also identified as potential mitigators of radiation damage that often were also radioprotective. Many of these compounds enhance DNA repair, have anti-inflammatory activity, and stimulate hematopoiesis. Selected compounds within these initial verified hits from both types of libraries identified potent mitigators of lethal whole body irradiation (WBI) in mice.

CONCLUSION

In spite of the fact that in vitro HTS has limitations and is unable to fully recapitulate all aspects of the complex in vivo acute radiation response, it identified several classes of molecules that had activity as radioprotectors and radiomitigators of the hematopoietic system in vivo. In the future, addition of 3-dimensional (3-D) or stem cell cultures or pathway analysis, may improve the power of HTS, but our findings indicate that common, evolutionary conserved, canonical pathways can be identified that could be exploited to mitigate radiation-induced defects.

A novel target of action of minocycline in NGF-induced neurite outgrowth in PC12 cells: translation initiation [corrected] factor eIF4AI

BACKGROUND

Minocycline, a second-generation tetracycline antibiotic, has potential activity for the treatment of several neurodegenerative and psychiatric disorders. However, its mechanisms of action remain to be determined.

METHODOLOGY/PRINCIPAL FINDINGS

We found that minocycline, but not tetracycline, significantly potentiated nerve growth factor (NGF)-induced neurite outgrowth in PC12 cells, in a concentration dependent manner. Furthermore, we found that the endoplasmic reticulum protein inositol 1,4,5-triphosphate (IP3) receptors and several common signaling molecules (PLC-γ, PI3K, Akt, p38 MAPK, c-Jun N-terminal kinase (JNK), mammalian target of rapamycin (mTOR), and Ras/Raf/ERK/MAPK pathways) might be involved in the active mechanism of minocycline. Moreover, we found that a marked increase of the eukaryotic translation initiation factor eIF4AI protein by minocycline, but not tetracycline, might be involved in the active mechanism for NGF-induced neurite outgrowth.

CONCLUSIONS/SIGNIFICANCE

These findings suggest that eIF4AI might play a role in the novel mechanism of minocycline. Therefore, agents that can increase eIF4AI protein would be novel therapeutic drugs for certain neurodegenerative and psychiatric diseases.

Therapeutic approaches to multiple sclerosis: an update on failed, interrupted, or inconclusive trials of immunomodulatory treatment strategies

Multiple sclerosis (MS) continues to be a therapeutic challenge, and much effort is being made to develop new and more effective immune therapies. Particularly in the past decade, neuroimmunologic research has delivered new and highly effective therapeutic options, as seen in the growing number of immunotherapeutic agents and biologics in development. However, numerous promising clinical trials have failed to show efficacy or have had to be halted prematurely because of unexpected adverse events. Some others have shown results that are of unknown significance with regard to a reliable assessment of true efficacy versus safety. For example, studies of the highly innovative monoclonal antibodies that selectively target immunologic effector molecules have not only revealed the impressive efficacy of such treatments, they have also raised serious concerns about the safety profiles of these antibodies. These results add a new dimension to the estimation of risk-benefit ratios regarding acute or long-term adverse effects. Therapeutic approaches that have previously failed in MS have indicated that there are discrepancies between theoretical expectations and practical outcomes of different compounds. Learning from these defeats helps to optimize future study designs and to reduce the risks to patients. This review summarizes trials on MS treatments since 2001 that failed or were interrupted, attempts to analyze the underlying reasons for failure, and discusses the implications for our current view of MS pathogenesis, clinical practice, and design of future studies. In order to maintain clarity, this review focuses on anti-inflammatory therapies and does not include studies on already approved and effective disease-modifying therapies, albeit used in distinct administration routes or under different paradigms. Neuroprotective and alternative treatment strategies are presented elsewhere.

Brain microglial cytokines in neurogenic hypertension

Accumulating evidence indicates a key role of inflammation in hypertension and cardiovascular disorders. However, the role of inflammatory processes in neurogenic hypertension remains to be determined. Thus, our objective in the present study was to test the hypothesis that activation of microglial cells and the generation of proinflammatory cytokines in the paraventricular nucleus (PVN) contribute to neurogenic hypertension. Intracerebroventricular infusion of minocycline, an anti-inflammatory antibiotic, caused a significant attenuation of mean arterial pressure, cardiac hypertrophy, and plasma norepinephrine induced by chronic angiotensin II infusion. This was associated with decreases in the numbers of activated microglia and mRNAs for interleukin (IL) 1beta, IL-6, and tumor necrosis factor-alpha, and an increase in the mRNA for IL-10 in the PVN. Overexpression of IL-10 induced by recombinant adenoassociated virus-mediated gene transfer in the PVN mimicked the antihypertensive effects of minocycline. Furthermore, acute application of a proinflammatory cytokine, IL-1beta, into the left ventricle or the PVN in normal rats resulted in a significant increase in mean arterial pressure. Collectively, this indicates that angiotensin II induced hypertension involves activation of microglia and increases in proinflammatory cytokines in the PVN. These data have significant implications on the development of innovative therapeutic strategies for the control of neurogenic hypertension.

Neuroinflammation in Huntington's disease

Huntington's disease (HD) is a monogenic neurodegenerative disease characterized by abnormal motor movements, personality changes and early death. In contrast to other neurodegenerative diseases, very little is known about the role of neuroinflammation in HD. While the current data clearly demonstrate the existence of inflammatory processes in HD pathophysiology, the question of whether neuroinflammation is purely reactive or might actively participate in disease pathogenesis is currently a matter of ongoing research and debate. This review will try to shed some light on the current state of research in this area and provide an outlook on potential future developments.