Semisynthetic Second-generation Tetracycline Research Articles

Possible Use of Minocycline in Adjunction to Intranasal Esketamine for the Management of Difficult to Treat Depression following Extensive Pharmacogenomic Testing: Two Case Reports

The advent of intra-nasal esketamine (ESK), one of the first so called fast-acting antidepressant, promises to revolutionize the management of treatment resistant depression (TRD). This NMDA receptor antagonist has proven to be rapidly effective in the short- and medium-term course of the illness, revealing its potential in targeting response in TRD. Although many TRD ESK responders are able to achieve remission, a considerable portion of them undergo a metamorphosis of their depression into different clinical presentations, characterized by instable responses and high recurrence rates that can be considered closer to the concept of Difficult to Treat Depression (DTD) than to TRD. The management of these DTD patients usually requires a further complex multidisciplinary approach and can benefit from the valuable contribution of new personalized medicine tools such as therapeutic drug monitoring and pharmacogenetics. Despite this, these patients usually come with long and complex previous treatments history and, often, advanced and sophisticated ongoing pharmacological schemes that can make the finding of new alternative options to face the current recurrences extremely challenging. In this paper, we describe two DTD patients—already receiving intranasal ESK but showing an instable course—who were clinically stabilized by the association with minocycline, a semisynthetic second-generation tetracycline with known and promising antidepressant properties.

In Situ Effects of Doxycycline on Neuromuscular Junction in Mice.

The antibacterial mechanism of doxycycline is known, but its effects on the nerve-muscle system are still not unclear. The aim of the study was to combine molecular targets of the neuromuscular machinery using the in situ neuronal blocker effect of doxycycline, a semisynthetic second-generation tetracycline derivative, on mice neuromuscular preparations. The effects of doxycycline were assessed on presynaptic, synaptic cleft, and postsynaptic neurotransmission, along with the muscle fiber, using the traditional myographic technique. Precisely, the effects of doxycycline were categorized into "all" or "nothing" effects depending on the concentration of doxycycline used; "all" was obtained with 4 μM doxycycline, and "nothing" was obtained with 1-3 μM doxycycline. The rationale of this study was to apply known pharmacological tools against the blocker effect of 4 μM doxycycline, such as F55-6 (Casearia sylvestris), CaCl2 (or Ca2+), atropine, neostigmine, polyethylene glycol (PEG 400), and d-Tubocurarine. The evaluation of cholinesterase enzyme activity and the diaphragm muscle histology were performed, and protocols on the neuromuscular preparation submitted to indirect or direct stimuli were complementary. Doxycycline does not affect cholinesterase activity nor causes damage to skeletal muscle diaphragm; it acts on ryanodine receptor, sarcolemmal membrane, and neuronal sodium channel with a postjunctional consequence due to the decreased availability of muscle nicotinic acetylcholine receptors. In conclusion, in addition to the neuronal blocker effect of doxycycline, we showed that doxycycline acts on multiple targets. It is antagonized by F55-6, a neuronal Na+-channel agonist, and Ca2+, but not by neostigmine.

Minocycline improves the recovery of nerve function and alleviates blood-brain barrier damage by inhibiting endoplasmic reticulum in traumatic brain injury mice model

Traumatic brain injury (TBI) is a clinical emergency with a very high incidence, disability, and fatality rate. Minocycline, a widely used semisynthetic second-generation tetracycline antibiotic, has anti-inflammatory and bactericidal effects. However, minocycline has not been explored as a therapeutic drug in TBI and if effective, the related molecular mechanism is also unclear. In this study, we examined the neuroprotective effect and possible mechanism of minocycline, in mice TBI model by studying the trauma-related functional and morphological changes. Also, in vitro cell studies were carried out to verify the animal model data. We found that minocycline significantly improved the neurobehavioral score, inhibited apoptosis, repaired the blood-brain barrier, and reduced the levels of inflammatory factors Interleukin-6 and tumor necrosis factor-α in TBI mice. In vitro, upon oxygen and glucose deprivation, minocycline reduced the levels of cellular inflammatory factors and increased the levels of tight junction and adherens junction proteins, thereby significantly improving the cell viability. Moreover, Mino treatment prevented the loss of tight junction and adherens junction proteins which were markedly reversed by an ER stress activator (tunicamycin) both in vivo and in vitro. Our findings set an effective basis for the clinical use of Mino to treat Traumatic brain injury-induced neurological deficits.

Tetracycline repurposing in neurodegeneration: focus on Parkinson's disease.

The prevalence of Parkinson's disease, which affects millions of people worldwide, is increasing due to the aging population. In addition to the classic motor symptoms caused by the death of dopaminergic neurons, Parkinson's disease encompasses a wide range of nonmotor symptoms. Although novel disease-modifying medications that slow or stop Parkinson's disease progression are being developed, drug repurposing, which is the use of existing drugs that have passed numerous toxicity and clinical safety tests for new indications, can be used to identify treatment compounds. This strategy has revealed that tetracyclines are promising candidates for the treatment of Parkinson's disease. Tetracyclines, which are neuroprotective, inhibit proinflammatory molecule production, matrix metalloproteinase activity, mitochondrial dysfunction, protein misfolding/aggregation, and microglial activation. Two commonly used semisynthetic second-generation tetracycline derivatives, minocycline and doxycycline, exhibit effective neuroprotective activity in experimental models of neurodegenerative/ neuropsychiatric diseases and no substantial toxicity. Moreover, novel synthetic tetracyclines with different biological properties due to chemical tuning are now available. In this review, we discuss the multiple effects and clinical properties of tetracyclines and their potential use in Parkinson's disease treatment. In addition, we examine the hypothesis that the anti-inflammatory activities of tetracyclines regulate inflammasome signaling. Based on their excellent safety profiles in humans from their use for over 50years as antibiotics, we propose the repurposing of tetracyclines, a multitarget antibiotic, to treat Parkinson's disease.

Burn-induced distant organ injury in rats and the effect of minocycline

Objectives: This study aimed to examine the anti-inflammatory potential of orally-administered minocycline, a semi-synthetic second-generation tetracycline, on burn-induced liver and kidney damage in rats. Materials and Methods: Female Sprague-Dawley rats (250- 300 g; n=7-8/group) were used. Burn and sham groups were exposed to 90 0C and 25 0C water bath for 10 s, respectively. Minocycline (20 mg/kg; twice daily; orogastrically) was administered for 24 h post-burn. After decapitation, trunk blood was collected for biochemical assays. Liver and kidneys were excised for histopathological evaluation and malondialdehyde (MDA), glutathione and chemiluminescence (CL) assays. Results: Minocycline treatment did not exert a significant effect on serum alanine aminotransferase, aspartate aminotransferase, blood urea nitrogen, and creatinine levels of the burn group. Increased serum total oxidant status of the burn group was reversed (P<0.001) and liver microscopic lesion score showed a slight reduction (P<0.01) by minocycline. Minocycline did not cause a significant effect on increased tissue MDA and glutathione levels of the burn group but reversed the elevated luminol CL levels (P<0.001, for liver and P<0.01, for kidney, respectively). Conclusion: Minocycline treatment to rats for 24 h post-burn was found to be effective to reduce oxidant production in the liver and kidney; however, it showed slight protection on these tissues against oxidant damage.

Minocycline supplementation for treatment of negative symptoms in early-phase schizophrenia: A double blind, randomized, controlled trial

BackgroundIt is difficult to improve negative symptoms and cognitive impairments in schizophrenia. A previous pilot study has shown that minocycline, a semi-synthetic second-generation tetracycline, is effective in treating for negative and/or cognitive symptoms in schizophrenia. ObjectivesThe present study was designed to examine the efficacy and safety of minocycline for the treatment of negative symptoms and cognitive impairments in patients with schizophrenia. MethodsNinety-two patients with early stage schizophrenia treated with risperidone entered this 16-week, double blind, randomized, placebo-controlled clinical trial. Subjects were randomly assigned to receive minocycline (200mg per day) or the placebo. The primary outcome was evaluated using the Scale for the Assessment of Negative Symptoms (SANS). Secondary outcomes included the response rate of SANS, the Positive and Negative Syndrome Scale (PANSS), the Clinical Global Impression Scale (CGI), and cognitive tests. ResultsSubjects receiving minocycline had greater improvements on SANS total scores and PANSS negative subscale scores (P<0.001) when compared with those receiving the placebo. Rates of treatment response (43.6%) in the minocycline group were significantly higher than those in the placebo group (10.0%) after 16weeks of treatment. There was no significant difference between the seven cognitive domains (P>0.05), except for the attention domain (P=0.044). ConclusionsThe addition of minocycline to atypical antipsychotic drugs in early schizophrenia had significant efficacy on negative symptoms but had a slight effect on the attention domains of patients with schizophrenia. It may be considered as a new adjunct treatment for negative symptoms of schizophrenia.Clinical trials.gov identifier: NCT01493622.

Impact of minocycline on neurodegenerative diseases in rodents: a meta-analysis

Minocycline is a semisynthetic second-generation tetracycline derivative, and many publications provide evidence of its successful neuroprotection in a variety of animal models. We searched PubMed and Chinese CNKI databases from January 1992 to May 2012 for studies on minocycline in neurodegenerative diseases in rodents. A meta-analysis that adopted weighted Cohen's d effect sizes, percent overlap, Fail-Safe N statistics, and confidence intervals was conducted. In total, 16 English and 3 Chinese articles with high or medium quality were included in this meta-analysis. The treatment benefits for rodents from low-dose (5 mg/kg/day), moderate-dose (45, 50, or 55 mg/kg/day), and high-dose (90 mg/kg/day) minocycline were larger in Huntington's disease, Alzheimer's disease, and stroke mouse models, respectively. In rats, a moderate dose (45 mg/kg/day) of minocycline was most effective. In conclusion, minocycline exerts neuroprotective effects in rodent models of neurodegenerative diseases. Anti-inflammatory, antiapoptotic, and antioxidant activities are discussed as the basis of this effect. However, there is insufficient information from these animal models on side effects of minocycline therapy.

Minocycline-Induced Bone Discoloration: A Case Report.

Minocycline is a semisynthetic second-generation tetracycline derivative that is widely used as a broad-spectrum antibiotic and anti-inflammatory agent1. Long-term treatment with tetracycline and its related derivatives causes discoloration and hyperpigmentation of the skin, bone, teeth, sclerae, thyroid, and oral mucosa2-11. Minocycline shares the same basic ringed structure found in other tetracyclines, with the exception of a dimethylamino group substitution at C7 and a functional group absence at C6. These differences in chemical structure result in more lipophilic properties than in other members of the tetracycline family12. Whereas tetracycline is known to cause discoloration in bone by oxidation-induced color change after binding irreversibly to hydroxyapatite, which is later deposited at the mineralization front on unmineralized mature osteoid, minocycline poorly chelates calcium and is thought to cause bone discoloration by a less well-understood mechanism13. Findings, including minocycline’s ability to discolor fully formed mature teeth as well as the presence of iron with trace amounts of calcium in minocycline-induced dark pigment, give credence to this idea14-16. Because of its lipophilic nature, minocycline is believed to achieve extensive tissue penetration, and in vitro protein-binding studies have also shown minocycline to bind collagen6,17. Once deposited, it is believed that minocycline is either degraded or lysosomally oxidized from its naturally yellow crystalline appearance to a black deposit3,18. Gross examination often reveals a bluish-gray or black discoloration of the bone and surrounding soft tissue, although these findings can be mutually exclusive1. The incidence of minocycline-induced discoloration of bone is unknown since it is more commonly found as an incidental finding during routine surgical procedures. However, staining of adult dentition has been reported to occur in 3% to 6% of patients on long-term minocycline …

Protective Effect of Minocycline Against Cisplatin-induced Ototoxicity

ObjectivesCisplatin, a widely used chemotherapeutic agent, has serious side effects, including nephrotoxicity and ototoxicity. Minocycline is a semisynthetic second-generation tetracycline that exerts anti-inflammatory and neuroprotective effects. The purpose of this study was to elucidate the protective effect of minocycline against cisplatin-induced ototoxicity in the auditory hair cell.MethodsThe House Ear Institute-Organ of Corti 1 (HEI-OC1) cell line and guinea pigs were used for in vitro and in vivo experiments. Cells were exposed to cisplatin with or without pre-treatment with minocycline. Cell survival was analyzed using MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide). Whole-cell lysates were collected and immunoblotted with antibodies against Bcl-2, p-c-Jun, active caspase-3, cleaved poly (ADP-ribose) polymerase (PARP), and apoptosis-inducing factor (AIF). The guinea pigs received intraperitoneal injections of cisplatin alone or following minocycline pretreatment. The auditory brainstem response was tested and the cochleae were harvested and evaluated using scanning electron microscopy.ResultsSurvival significantly increased in cells pretreated with minocycline compared with cells exposed to cisplatin alone. Cisplatin treatment increased the expression of active caspase 3, p-c Jun, PARP, and AIF, and pretreatment with minocycline attenuated this response. In animal study, the threshold shift by cisplatin injection in the auditory brainstem response was less pronounced in animals pretreated with minocycline. Scanning electron microscopy revealed more severe damage to the outer hair cells at the basal and middle turns than the apical turn.ConclusionMinocycline partially protects against cisplatin-induced ototoxicity via both caspase-dependent and independent apoptosis pathways.

Minocycline attenuates both OGD-induced HMGB1 release and HMGB1-induced cell death in ischemic neuronal injury in PC12 cells

High mobility group box-1 (HMGB1), a non-histone DNA-binding protein, is massively released into the extracellular space from neuronal cells after ischemic insult and exacerbates brain tissue damage in rats. Minocycline is a semisynthetic second-generation tetracycline antibiotic which has recently been shown to be a promising neuroprotective agent. In this study, we found that minocycline inhibited HMGB1 release in oxygen–glucose deprivation (OGD)-treated PC12 cells and triggered the activation of p38mitogen-activated protein kinase (MAPK) and extracellular signal-regulated kinases (ERK1/2). The ERK kinase (MEK)1/2 inhibitor U-0126 and p38MAPK inhibitor SB203580 blocked HMGB1 release in response to OGD. Furthermore, HMGB1 triggered cell death in a dose-dependent fashion. Minocycline significantly rescued HMGB1-induced cell death in a dose-dependent manner. In light of recent observations as well as the good safety profile of minocycline in humans, we propose that minocycline might play a potent neuroprotective role through the inhibition of HMGB1-induced neuronal cell death in cerebral infarction.

Minocycline prevents Aβ(25–35)-induced reduction of somatostatin and neprilysin content in rat temporal cortex

Aims Tetracyclines have been demonstrated to inhibit formation of β-amyloid (Aβ) aggregates and to disassemble preformed fibrils. Minocycline, a semi-synthetic second-generation tetracycline, can reverse Aβ-induced impairment of cognitive functions. Since somatostatin is involved in cognition and we recently showed that Aβ(25–35) lowers somatostatin expression in the rat temporal cortex, our aim here was to analyze the effects of minocycline on somatostatin immunoreactivity and mRNA levels in the temporal cortex of Aβ(25–35)-infused and healthy rats. Moreover, since brain levels of neprilysin, an Aβ-degrading enzyme, decrease with age, favoring the appearance of senile neuritic plaques, we tested whether minocyline could affect neprilysin expression. Main methods Wistar rats were thus injected with minocycline twice on the first day of treatment. On the following day, and during 14 days, Aβ(25–35) or vehicle were administered. Minocycline was injected once again on days 13 and 14. All animals were sacrificed 24 h after the last drug injection. Key findings Minocycline abrogated the Aβ(25–35)-induced decrease of somatostatin-like immunoreactive content, somatostatin mRNA levels, phosphorylated-CREB content and neprilysin levels. Minocycline alone enhanced these targets. Significance Our findings indicate that minocycline prevents the deleterious effects of Aβ(25–35) on SRIF and neprilysin expression in the rat temporal cortex and that it has protective effects per se on these parameters.

Minocycline provides protection against β-amyloid(25-35)-induced alterations of the somatostatin signaling pathway in the rat temporal cortex

Minocycline is a semi-synthetic second-generation tetracycline known to improve cognition in amyloid precursor protein transgenic mice. Whether it can protect the somatostatin (SRIF) receptor-effector system, also involved in learning and memory, from alterations induced by chronic i.c.v. infusion of β-amyloid peptide (Aβ)(25-35) is presently unknown. Hence, in the present study, we tested the effects of minocycline on the SRIF signaling pathway in the rat temporal cortex. To this end, male Wistar rats were injected with minocycline (45 mg/kg body weight) i.p. twice on the first day of treatment. On the following day and during 14 days, Aβ(25-35) was administered i.c.v. via an osmotic minipump connected to a cannula implanted in the left lateral ventricle (300 pmol/day). Minocycline (22.5 mg/kg, i.p.) was injected once again the last 2 days of the Aβ(25-35) infusion. The animals were killed by decapitation 24 h after the last drug injection. Our results show that minocycline prevents the decrease in SRIF receptor density and somatostatin receptor (sst) 2 expression and the attenuated capacity of SRIF to inhibit adenylyl cyclase (AC) activity, alterations present in the temporal cortex of Aβ(25-35)-treated rats. Furthermore, minocycline blocks the Aβ(25-35)-induced decrease in phosphorylated cyclic AMP (cAMP) response element binding protein (p-CREB) content and G-protein-coupled receptor kinase 2 (GRK) protein expression in this brain area. Altogether, the present data demonstrate that minocycline in vivo provides protection against Aβ-induced impairment of the SRIF signal transduction pathway in the rat temporal cortex and suggest that it may have a potential as a therapeutic agent in human Alzheimer's disease, although further studies are warranted.

Minocycline neuroprotects, reduces microglial activation, inhibits caspase 3 induction, and viral replication following Japanese encephalitis

Minocycline is broadly protective in neurological disease models featuring inflammation and cell death and is being evaluated in clinical trials. Japanese encephalitis virus (JEV) is one of the most important causes of viral encephalitis worldwide. There is no specific treatment for Japanese encephalitis (JE) and no effective antiviral drugs have been discovered. Studies indicate that JE involves profound neuronal loss as well as secondary inflammation caused because of cell death. Minocycline is a semisynthetic second-generation tetracycline that exerts anti-inflammatory and antiapoptotic effects that are completely separate from its antimicrobial action. Because tetracycline treatment is clinically well tolerated, we investigated whether minocycline protects against experimental model of JE. Intravenous inoculation of GP78 strain of JEV in adult mice results in lethal encephalitis and caused primarily because of neuronal death and secondary inflammation caused because of cell death. Minocycline confers complete protection in mice following JEV infection (p < 0.0001). Neuronal apoptosis, microglial activation, active caspase activity, proinflammatory mediators, and viral titer were markedly decreased in minocycline-treated JEV infected mice on ninth day post-infection. Treatment with minocycline may act directly on brain cells, because neuronal cell line Neuro2a were also salvaged from JEV-induced death. Our data suggest that minocycline may be a candidate to consider in human clinical trials for JE patients.

Protective effect of minocycline, a semi-synthetic second-generation tetracycline against 3-nitropropionic acid (3-NP)-induced neurotoxicity

3-Nitropropionic acid (3-NP) is an irreversible inhibitor of the electron transport enzyme succinate dehydrogenase, a mitochondrial Complex II enzyme. Minocycline is a semi-synthetic second-generation tetracycline with neuroprotective activity and has the capability to effectively cross the blood–brain barrier. We investigated the effects of minocycline on behavioral, biochemical, inflammation related and neurochemical alterations induced by the sub-chronic administration of 3-nitropropionic acid to rats. Chronic pre-administration of minocycline (50 and 100 mg/kg) dose dependently prevented 3-NP-induced dysfunction behavioral (hypoactivity, memory retention, locomotor and rota-rod activity). In addition, 3-NP produced a marked increase in lipid peroxidation levels whereas decreased the activities of catalase and succinate dehydrogenase. In contrast, pretreatment of 3-NP injected rats with minocycline resulted in the attenuation of all these alterations. A marked increase in an inflammatory cytokine TNF-α by 3-NP was also decreased by minocycline treatment. Neurochemically, the administration of 3-NP significantly decreased the levels of catecholamines in the brain homogenates (dopamine, norepinephrine and serotonin) which were reversed by pretreatment of minocycline. The present finding explains the neuroprotective effect of minocycline against 3-NP toxicity by virtue of its antioxidant and anti-inflammatory activity.

FC4E A PRACTICAL CLINICAL TRIAL COMPARING HALOPERIDOL, RISPERIDONE AND OLANZAPINE FOR THE ACUTE TREATMENT OF FIRST EPISODE OF NON-AFFECTIVE PSYCHOSIS

It is difficult to improve negative symptoms and cognitive impairments in schizophrenia. A previous pilot study has shown that minocycline, a semi-synthetic second-generation tetracycline, is effective in treating for negative and/or cognitive symptoms in schizophrenia.The present study was designed to examine the efficacy and safety of minocycline for the treatment of negative symptoms and cognitive impairments in patients with schizophrenia.Ninety-two patients with early stage schizophrenia treated with risperidone entered this 16-week, double blind, randomized, placebo-controlled clinical trial. Subjects were randomly assigned to receive minocycline (200 mg per day) or the placebo. The primary outcome was evaluated using the Scale for the Assessment of Negative Symptoms (SANS). Secondary outcomes included the response rate of SANS, the Positive and Negative Syndrome Scale (PANSS), the Clinical Global Impression Scale (CGI), and cognitive tests.Subjects receiving minocycline had greater improvements on SANS total scores and PANSS negative subscale scores (P < 0.001) when compared with those receiving the placebo. Rates of treatment response (43.6%) in the minocycline group were significantly higher than those in the placebo group (10.0%) after 16 weeks of treatment. There was no significant difference between the seven cognitive domains (P > 0.05), except for the attention domain (P = 0.044).The addition of minocycline to atypical antipsychotic drugs in early schizophrenia had significant efficacy on negative symptoms but had a slight effect on the attention domains of patients with schizophrenia. It may be considered as a new adjunct treatment for negative symptoms of schizophrenia.Clinical trials.gov identifier: NCT01493622.

Inhibitory action of minocycline on lipopolysaccharide-induced release of nitric oxide and prostaglandin E2 in BV2 microglial cells.

Microglia are the major inflammatory cells in the central nervous system and become activated in response to brain injuries such as ischemia, trauma, and neurodegenerative diseases including Alzheimer's disease (AD). Moreover, activated microglia are known to release a variety of proinflammatory cytokines and oxidants such as nitric oxide (NO). Minocycline is a semisynthetic second-generation tetracycline that exerts anti-inflammatory effects that are completely distinct form its antimicrobial action. In this study, the inhibitory effects of minocycline on NO and prostaglandin E2 (PGE2) release was examined in lipopolysaccharides (LPS)-challenged BV2 murine microglial cells. Further, effects of minocycline on inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression levels were also determined. The results showed that minocycline significantly inhibited NO and PGE2 production and iNOS and COX-2 expression in BV2 microglial cells. These findings suggest that minocycline should be evaluated as potential therapeutic agent for various pathological conditions due to the excessive activation of microglia.

Minocycline blocks nitric oxide-induced neurotoxicity by inhibition p38 MAP kinase in rat cerebellar granule neurons

Minocycline, a semisynthetic second-generation tetracycline, was reported to have neuroprotective effects in models of global and focal cerebral ischemia, the R6/2 mouse model of Huntington disease, as well as glutamate-induced neurotoxicity in mixed neuronal/glial cultures. It was suggested that neuroprotective effects of minocycline resulted from inhibition of microglial/astroglial activation ‘Proc. Natl. Acad. Sci. USA 95 1998 15769’. To determine whether or not minocycline is able to directly protect neurons against injury insults and to delineate its neuroprotective mechanism(s), we treated cultured rat cerebellar granule neurons (CGN) with nitric oxide (NO) in the presence or absence of minocycline. We found that minocycline protected neurons against NO-induced neuronal death in a concentration-dependent fashion. Consistent to other reports, NO was able to induce p38 MAP kinase phosphorylation at 3–6 h and such an induction could be significantly inhibited by minocycline. Furthermore, SB 203580, a p38 MAP kinase inhibitor, almost completely attenuated NO-induced neuronal death of CGN as well. These results suggest that minocycline is able to block NO-induced neurotoxicity in CGN by inhibiting NO-induced phosphorylation of p38 MAP kinase. Our finding may explain the neuroprotective mechanism of minocycline in those neurodegenerative models.

A tetracycline derivative, minocycline, reduces inflammation and protects against focal cerebral ischemia with a wide therapeutic window.

The only treatment of patients with acute ischemic stroke is thrombolytic therapy, which benefits only a fraction of stroke patients. Both human and experimental studies indicate that ischemic stroke involves secondary inflammation that significantly contributes to the outcome after ischemic insult. Minocycline is a semisynthetic second-generation tetracycline that exerts antiinflammatory effects that are completely separate from its antimicrobial action. Because tetracycline treatment is clinically well tolerated, we investigated whether minocycline protects against focal brain ischemia with a wide therapeutic window. Using a rat model of transient middle cerebral artery occlusion, we show that daily treatment with minocycline reduces cortical infarction volume by 76 +/- 22% when the treatment is started 12 h before ischemia and by 63 +/- 35% when started even 4 h after the onset of ischemia. The treatment inhibits morphological activation of microglia in the area adjacent to the infarction, inhibits induction of IL-1beta-converting enzyme, and reduces cyclooxygenase-2 expression and prostaglandin E(2) production. Minocycline had no effect on astrogliosis or spreading depression, a wave of ionic transients thought to contribute to enlargement of cortical infarction. Treatment with minocycline may act directly on brain cells, because cultured primary neurons were also salvaged from glutamate toxicity. Minocycline may represent a prototype of an antiinflammatory compound that provides protection against ischemic stroke and has a clinically relevant therapeutic window.