Tigecycline is a novel glycylcycline antibacterial drug, which shows both antibiotic function and anti-tumor activity. This review summarizes the single and combined use of tigecycline for tumor treatment and the underpinning mechanisms. As an inhibitor for mitochondrial DNA translation, tigecycline affects the proliferation, migration, and invasion of tumor cells mainly through inhibiting mitochondrial protein synthesis and inducing mitochondrial dysfunction. Although the effect of tigecycline monotherapy is controversial, the efficacy of combined use of tigecycline is satisfactory. Therefore, it is important to explore the molecular mechanisms underpinning the anti-tumor activity of tigecycline, with the aim to use it as a cheap and effective new anti-tumor drug.
Anti-Bacterial Agents/pharmacology* ; Humans ; Minocycline/pharmacology* ; Mitochondria ; Neoplasms/drug therapy* ; Tigecycline/pharmacology*

Acinetobacter baumannii ; drug effects ; Anti-Bacterial Agents ; pharmacology ; Carbapenems ; pharmacology ; Drug Resistance, Bacterial ; Microbial Sensitivity Tests ; Minocycline ; analogs & derivatives ; pharmacology

Objective To examine the neuroanatomical substrates underlying the effects of minocycline in alleviating lipopolysaccharide (LPS)-induced neuroinflammation. Methods Forty C57BL/6 male mice were randomly and equally divided into eight groups. Over three conse-cutive days, saline was administered to four groups of mice and minocycline to the other four groups. Immediately after the administration of saline or minocycline on the third day, two groups of mice were additionally injected with saline and the other two groups were injected with LPS. Six or 24 hours after the last injection, mice were sacrificed and the brains were removed. Immunohistochemical staining across the whole brain was performed to detect microglia activation via Iba1 and neuronal activation via c-Fos. Morphology of microglia and the number of c-Fo-positive neurons were analyzed by Image-Pro Premier 3D. One-way ANOVA and Fisher's least-significant differences were employed for statistical analyses. Results Minocycline alleviated LPS-induced neuroinflammation as evidenced by reduced activation of microglia in multiple brain regions, including the shell part of the nucleus accumbens (Acbs), paraventricular nucleus (PVN) of the hypothalamus, central nucleus of the amygdala (CeA), locus coeruleus (LC), and nucleus tractus solitarius (NTS). Minocycline significantly increased the number of c-Fo-positive neurons in NTS and area postrema (AP) after LPS treatment. Furthermore, in NTS-associated brain areas, including LC, lateral parabrachial nucleus (LPB), periaqueductal gray (PAG), dorsal raphe nucleus (DR), amygdala, PVN, and bed nucleus of the stria terminali (BNST), minocycline also significantly increased the number of c-Fo-positive neurons after LPS administration. Conclusion Minocycline alleviates LPS-induced neuroinflammation in multiple brain regions, possibly due to increased activation of neurons in the NTS-associated network.
Animals ; Female ; Lipopolysaccharides/toxicity* ; Male ; Mice ; Mice, Inbred C57BL ; Minocycline/pharmacology* ; Neuroinflammatory Diseases ; Solitary Nucleus

BACKGROUNDVancomycin-resistant Enterococci (VRE) cause serious infections that are difficult to treat. We carried out this study to determine the mutant prevention concentration (MPC) of linezolid when combined with minocycline against VRE strains, to determine the mechanism of drug resistance in vitro, and to provide a theoretical basis for the rational use of drugs against VRE.

METHODSThe minimum inhibitory concentrations (MICs) of linezolid and minocycline against 30 Enterococci (E.) isolates (including 20 VRE strains) were determined by the broth microdilution method. Drug interactions were assessed by the checkerboard microdilution tests and confirmed by time-kill studies. Two vancomycin-susceptible strains N27 and N40 (linezolid MIC, 2 g/ml; minocycline MIC, 4 µg/ml) and control strains E. faecalis ATCC 29212 and ATCC 51299 were also tested. The MPCs of linezolid and minocycline (alone and combined) were determined using the agar dilution method. Strains showing stable resistance were analyzed by polymerase chain reaction (PCR) amplification of domain V of the 23S rRNA gene.

RESULTSCheckerboard titration studies revealed synergistic effects of combination therapy in 26.7% of 30 E. isolates. Antagonism was not observed. The G2576U mutation was detected in stable linezolid-resistant strains of ATCC 29212, N40, and N27 before and after resistance screening, and MIC values increased with the number of G2576U mutations. The MPC of linezolid against E. decreased dramatically when combined with minocycline, and vice versa.

CONCLUSIONLinezolid or minocycline alone produce resistant strains; however, their joint use may reduce the MPC of each agent against VRE, thereby decreasing resistant mutants and bacterial infections.

Acetamides ; pharmacology ; Anti-Bacterial Agents ; pharmacology ; Anti-Infective Agents ; pharmacology ; Drug Therapy, Combination ; Enterococcus ; drug effects ; genetics ; Linezolid ; Microbial Sensitivity Tests ; Minocycline ; pharmacology ; Mutation ; Oxazolidinones ; pharmacology ; Vancomycin Resistance

We determined the antimicrobial susceptibility of 90 clinical isolates of Stenotrophomonas maltophilia collected in 2009 at a tertiary care hospital in Korea. Trimethoprim-sulfamethoxazole, minocycline, and levofloxacin were active against most of the isolates tested. Moxifloxacin and tigecycline were also active and hold promise as therapeutic options for S. maltophilia infections.
Anti-Infective Agents/*pharmacology ; Hospitals ; Korea ; Microbial Sensitivity Tests ; Minocycline/pharmacology ; Ofloxacin/pharmacology ; Stenotrophomonas maltophilia/*drug effects ; Trimethoprim-Sulfamethoxazole Combination/pharmacology

Microglia are important cells involved in the regulation of neuropathic pain (NPP) and morphine tolerance. Information on their plasticity and polarity has been elucidated after determining their physiological structure, but there is still much to learn about the role of this type of cell in NPP and morphine tolerance. Microglia mediate multiple functions in health and disease by controlling damage in the central nervous system (CNS) and endogenous immune responses to disease. Microglial activation can result in altered opioid system activity, and NPP is characterized by resistance to morphine. Here we investigate the regulatory mechanisms of microglia and review the potential of microglial inhibitors for modulating NPP and morphine tolerance. Targeted inhibition of glial activation is a clinically promising approach to the treatment of NPP and the prevention of morphine tolerance. Finally, we suggest directions for future research on microglial inhibitors.
Humans ; Calcitonin Gene-Related Peptide/antagonists & inhibitors* ; Drug Tolerance ; Hypoglycemic Agents/pharmacology* ; Microglia/physiology* ; MicroRNAs/physiology* ; Minocycline/pharmacology* ; Morphine/pharmacology* ; Neuralgia/etiology* ; Plant Extracts/pharmacology* ; Signal Transduction/physiology*

This study examined the protective effect of ischemic postconditioning (IPoC) and minocycline postconditioning (MT) on myocardial ischemia-reperfusion (I/R) injury in atherosclerosis (AS) animals and the possible mechanism. Forty male healthy rabbits were injected with bovine serum albumin following feeding on a high fat diet for 6 weeks to establish AS model. AS rabbits were randomly divided into 3 groups: (1) I/R group, the rabbits were subjected to myocardial ischemia for 35 min and then reperfusion for 12 h; (2) IPoC group, the myocardial ischemia lasted for 35 min, and then reperfusion for 20 s and ischemia for 20 s [a total of 3 cycles (R20s/I20s×3)], and then reperfusion was sustained for 12 h; (3) MT group, minocycline was intravenously injected 10 min before reperfusion. The blood lipids, malondialdehyde (MDA), superoxide dismutase (SOD), soluble cell adhesion molecule (sICAM), myeloperoxidase (MPO), and cardiac troponin T (cTnT) were biochemically determined. The myocardial infarction size (IS) and apoptosis index (AI) were measured by pathological examination. The expression of bcl-2 and caspase-3 was detected in the myocardial tissue by using reverse transcription-polymerase chain reaction (RT-PCR). The results showed that the AS models were successfully established. The myocardial IS, the plasma levels of MDA, sICAM, MPO and cTnT, and the enzymatic activity of MPO were significantly decreased, and the plasma SOD activity was significantly increased in IPoC group and MT group as compared with I/R group (P<0.05 for all). The myocardial AI and the caspase-3 mRNA expression were lower and the bcl-2 mRNA expression was higher in IPoC and MT groups than those in I/R group (all P<0.05). It is concluded that the IPoC and MT can effectively reduce the I/R injury in the AS rabbits, and the mechanisms involved anti-oxidation, anti-inflammation, up-regulation of bcl-2 expression and down-regulation of caspase-3 expression. Minocycline can be used as an effective pharmacologic postconditioning drug to protect myocardia from I/R injury.
Animals ; Atherosclerosis ; physiopathology ; Ischemic Preconditioning, Myocardial ; methods ; Male ; Minocycline ; pharmacology ; Myocardial Reperfusion Injury ; physiopathology ; Rabbits ; Reperfusion Injury ; physiopathology

OBJECTIVETo investigate the effect of minocycline on hyperpolarization-activated current (Ih) in the substantia gelatinosa (SG) neurons in rat spinal dorsal horn.

METHODSIn vitro spinal cord transverse slices were prepared from 3-5-week-old male Sprague-Dawley rats. Using whole-cell patch clamp technique, Ih currents were recorded before and after bath application of minocycline (1-300 µmol/L) to the SG neurons.

RESULTSIh currents were observed in nearly 50% of the recorded neurons, and were blocked by Ih blocker CsCl and ZD7288. Minocycline rapidly and reversibly reduced the amplitude of Ih and decreased the current density in a concentration-dependent manner with an IC50 of 34 µmol/L.

CONCLUSIONMinocycline suppresses the excitability of SG neurons through inhibiting the amplitude and current density of Ih and thereby contributes to pain modulation.

Animals ; Male ; Minocycline ; pharmacology ; Neurons ; drug effects ; Patch-Clamp Techniques ; Rats ; Rats, Sprague-Dawley ; Substantia Gelatinosa ; cytology

INTRODUCTIONTigecycline is an antibiotic belonging to the glycylcycline class with in vitro activity against most Gram-negative bacteria, other than Pseudomonas aeruginosa. This study investigated the in vitro activity of tigecycline against multi-resistant isolates of Enterobacteriaceae and Acinetobacter spp. isolated from clinical specimens in Singapore.

MATERIALS AND METHODSMinimum inhibitory concentrations (MICs) to tigecycline were determined for 173 isolates of multi-resistant Escherichia coli, Klebsiella spp., Enterobacter spp. and Acinetobacter spp. using agar dilution.

RESULTSThe MIC required to inhibit the growth of 90% of organisms varied from 0.5 to 4 mg/L for the study isolates. Based on a resistance breakpoint of >or=8 mg/L, resistance rates varied from 0% to 9%.

CONCLUSIONSTigecycline demonstrates good in vitro activity against multi-resistant strains of Enterobacteriaceae, with more variable activity against multi-resistant strains of Acinetobacter spp.

Acinetobacter ; drug effects ; Anti-Bacterial Agents ; pharmacology ; Drug Resistance, Multiple, Bacterial ; Enterobacteriaceae ; drug effects ; Escherichia coli ; drug effects ; Klebsiella ; drug effects ; Minocycline ; analogs & derivatives ; pharmacology ; Singapore

OBJECTIVE: To unravel the underlying mechanism of minocycline in formalin-induced inflammatory pain, and to investigate the effects of minocycline on synaptic transmission in substantia gela-tinosa (SG) neurons of rat spinal dorsal horn. METHODS: Behavioral and immunohistochemistry experiments: 30 male Sprague-Dawley (SD) rats (3-5 weeks old) were randomly assigned to control (n=8 rats), model (n=8 rats), saline treatment model (n=6 rats) and minocycline treatment model (n=8 rats) groups. The control group was subcutaneously injected with normal saline on the right hindpaws. Acute inflammatory pain model was established by injecting 5% (volume fraction) formalin into the right hindpaws. The rats in the latter two groups received intraperitoneal injection of saline and minocycline 1 h before the formalin injection, respectively. The time of licking and lifting was recorded every 5 min within 1 h after the subcutaneous injection of normal saline or formalin for all the groups, which was continuously recorded for 1 h. One hour after the pain behavioral recording, the spinal cord tissue was removed following transcardial perfusion of 4% paraformaldehyde. The expression of c-Fos protein in spinal dorsal horn was observed by immunohistochemistry. Electrophysiological experiment: In vitro whole-cell patch-clamp recordings were performed in spinal cord parasagittal slices obtained from 26 male SD rats (3-5 weeks old). Two to five neurons were randomly selected from each rat for patch-clamp recording. the effects of minocycline, fluorocitrate and doxycycline on spontaneous excitatory postsynaptic currents (sEPSCs) or spontaneous inhibitory postsynaptic currents (sIPSCs) of SG neurons were investigated. RESULTS: Compared with the control group, both the licking and lifting time and the expression of c-Fos protein in ipsilateral spinal dorsal horn of the model group were significantly increased. Intraperitoneal injection of minocycline largely attenuated the second phase of formalin-induced pain responses (t=2.957, P<0.05). Moreover, c-Fos protein expression was also dramatically reduced in both the superficial lamina (I-II) and deep lamina (III-IV) of spinal dorsal horn (t_I-II=3.912, t_III-IV=2.630, P<0.05). On the other side, bath application of minocycline significantly increased the sIPSCs frequency to 220%±10% (P<0.05) of the control but did not affect the frequency (100%±1%, t=0.112, P=0.951) and amplitude (98%±1%, t=0.273, P=0.167) of sEPSCs and the amplitude (105%±3%, t=0.568, P=0.058) of sIPSCs. However, fluorocitrate and doxycycline had no effect on the frequency [(99%±1%, t=0.366, P=0.099); (102%±1%, t=0.184, P=0.146), respectively] and amplitude [(98%±1%, t=0.208, P=0.253); (99%±1%, t=0.129, P=0.552), respectively] of sIPSCs. CONCLUSION Minocycline can inhibit formalin-induced inflammatory pain and the expression of c-Fos protein in spinal dorsal horn. These effects are probably due to its enhancement in inhibitory synaptic transmission of SG neurons but not its effect on microglial activation or antibiotic action.
Animals ; Anti-Bacterial Agents/pharmacology* ; Formaldehyde ; Inflammation/complications* ; Inhibitory Postsynaptic Potentials ; Male ; Minocycline/pharmacology* ; Pain/prevention & control* ; Random Allocation ; Rats ; Rats, Sprague-Dawley ; Spinal Cord