1,12-Substituted tetracyclines as antioxidant agents

Chromomycin, an antibiotic produced by Streptomyces flaviscleroticus might play a role in the resistance to oxidative stress and is essential for viability in stationary phase

The well-known role of antibiotics in killing sensitive organisms has been challenged by the effects they exert at subinhibitory concentrations. Unfortunately, there are very few published reports on the advantages these molecules may confer to their producers. This study describes the construction of a genetically verified deletion mutant of Streptomyces flaviscleroticus unable to synthesize chromomycin. This mutant was characterized by a rapid loss of viability in stationary phase that was correlated with high oxidative stress and altered antioxidant defences. Altered levels of key metabolites in the mutant signalled a redistribution of the glycolytic flux toward the PPP to generate NADPH to fight oxidative stress as well as reduction of ATP-phosphofructokinase and Krebs cycle enzymes activities. These changes were correlated with a shift in the preference for carbon utilization from glucose to amino acids. Remarkably, chromomycin at subinhibitory concentration increased longevity of the non-producer and restored most of the phenotypic features' characteristic of the wild type strain. Altogether these observations suggest that chromomycin may have antioxidant properties that would explain, at least in part, some of the phenotypes of the mutant. Our observations warrant reconsideration of the secondary metabolite definition and raise the possibility of crucial roles for their producers.

Current progress on antioxidants incorporating the pyrazole core

The search of new antioxidants, as drugs candidates, is an active field of medicinal chemistry. The synthesis of compounds with antioxidant potential has increased in recent years and a high number of structurally diverse compounds have been published. This review aims to show the current state-of-the-art on the development of antioxidant compounds incorporating the pyrazole pharmacophore. It is a well-timed review driven by the increasing number of papers, on this issue, that have been published since the beginning of the 21st century (from 2000 to 2017). The aim is to look deeper into the structures already published in the literature containing the pyrazole core as the unique pharmacophore or combined with other pharmacophores and see the relationship between the presence of this five-membered nitrogen heterocycle and the behaviour of the compounds as potential antioxidant agents. An attempt was made to whenever possible establish structure-activity relationships that could help the design of new and more potent antioxidant agents containing this important pharmacophore.

A minocycline derivative reduces nerve injury-induced allodynia, LPS-induced prostaglandin E2 microglial production and signaling via toll-like receptors 2 and 4

Many studies have shown that minocycline, an antibacterial tetracycline, suppresses experimental pain. While minocycline's positive effects on pain resolution suggest that clinical use of such drugs may prove beneficial, minocycline's antibiotic actions and divalent cation (Ca(2+); Mg(2+)) chelating effects detract from its potential utility. Thus, we tested the antiallodynic effect induced by a non-antibacterial, non-chelating minocycline derivative in a model of neuropathic pain and performed an initial investigation of its anti-inflammatory effects in vitro. Intraperitoneal minocycline (100mg/kg) and 12S-hydroxy-1,12-pyrazolinominocycline (PMIN; 23.75 mg/kg, 47.50mg/kg or 95.00 mg/kg) reduce the mechanical allodynia induced by chronic constriction injury of mouse sciatic nerve. PMIN reduces the LPS-induced production of PGE2 by primary microglial cell cultures. Human embryonic kidney cells were transfected to express human toll-like receptors 2 and 4, and the signaling via both receptors stimulated with PAM3CSK4 or LPS (respectively) was affected either by minocycline or PMIN. Importantly, these treatments did not affect the cell viability, as assessed by MTT test. Altogether, these results reinforce the evidence that the anti-inflammatory and experimental pain suppressive effects induced by tetracyclines are neither necessarily linked to antibacterial nor to Ca(2+) chelating activities. This study supports the evaluation of the potential usefulness of PMIN in the management of neuropathic pain, as its lack of antibacterial and Ca(2+) chelating activities might confer greater safety over conventional tetracyclines.

Lipid peroxidation is not the primary mechanism of bilirubin-induced neurologic dysfunction in jaundiced Gunn rat pups

BACKGROUND

Hazardous levels of bilirubin produce oxidative stress in vitro and may play a role in the genesis of bilirubin-induced neurologic dysfunction (BIND). We hypothesized that the antioxidants taurourosdeoxycholic acid (TUDCA), 12S-hydroxy-1,12-pyrazolinominocycline (PMIN), and minocycline (MNC) inhibit oxidative stress and block BIND in hyperbilirubinemic j/j Gunn rat pups that were given sulfadimethoxine to induce bilirubin encephalopathy.

METHODS

At peak postnatal hyperbilirubinemia, j/j Gunn rat pups were dosed with sulfadimethoxine to induce bilirubin encephalopathy. Pups were given TUDCA, PMIN, MNC, or vehicle pretreatment (15 min before sulfadimethoxine). After 24 h, BIND was scored by using a rating scale of neurobehavior and cerebellar tissue 4-hydroxynonenal and protein carbonyl dinitrophenyl content were determined. Nonjaundiced heterozygous N/j pups served as controls.

RESULTS

Administration of sulfadimethoxine induced BIND and lipid peroxidation but not protein oxidation in hyperbilirubinemic j/j pups. TUDCA, PMIN, and MNC each reduced lipid peroxidation to basal levels observed in nonjaundiced N/j controls, but only MNC prevented BIND.

CONCLUSION

These findings show that lipid peroxidation inhibition alone is not sufficient to prevent BIND. We speculate that the neuroprotective efficacy of MNC against BIND involves action(s) independent of, or in addition to, its antioxidant effects.

Tetracyclines and pain

Tetracyclines are natural or semi-synthetic bacteriostatic agents which have been used since late 1940s against a wide range of gram-positive and gram-negative bacteria and atypical organisms such as chlamydia, mycoplasmas, rickettsia, and protozoan parasites. After the discovery of the first tetracyclines, a second generation of compounds was sought in order to improve water solubility for parenteral administration or to enhance bioavailability after oral administration. This approach resulted in the development of doxycycline and minocycline in the 1970s. Doxycycline was included in the World Health Organization Model List of Essential Medicines either as antibacterial or to prevent malaria or to treat patients with this disease. Additional development led to the third generation of tetracyclines, being tigecycline the only medicine of this class to date. Besides antibacterial activities, the anti-inflammatory, antihypernociceptive and neuroprotective activities of tetracyclines began to be widely studied in the late 1990s. Indeed, there has been an increasing interest in investigating the effects induced by minocycline as this liposoluble derivative is known to cross the blood-brain barrier to the greatest extent. Minocycline induces antihypernociceptive effects in a wide range of animal models of nociceptive, inflammatory and neuropathic pain. In this study, we discuss the antihypernociceptive activity of tetracyclines and summarise its underlying cellular and molecular mechanisms.

A novel non-antibacterial, non-chelating hydroxypyrazoline derivative of minocycline inhibits nociception and oedema in mice

BACKGROUND AND PURPOSE

Many in vitro and fewer in vivo studies have shown that tetracyclines present anti-inflammatory activity. We investigated if a novel non-antibacterial, non-chelating hydroxypyrazoline derivative of minocycline, 12S-hydroxy-1,12-pyrazolinominocycline (PMIN), also induced antinociceptive and anti-inflammatory effects.

EXPERIMENTAL APPROACH

Antibacterial effects against a minocycline-sensitive Staphylococcus aureus strain were evaluated by applying a cylinder-plate agar diffusion technique. Antibacterial effects of diluted serum from mice pre-treated with minocycline or PMIN were also evaluated. Ca2+ binding activity was assessed by spectrophotometry. Formalin-induced nociceptive responses and carrageenan-induced paw oedema were evaluated in mice. The rota-rod apparatus was used to evaluate motor coordination.

KEY RESULTS

Minocycline, but not PMIN, inhibited bacterial growth. Serum from mice treated with minocycline, but not with PMIN, also induced such an effect. The UV absorption spectrum of solutions of minocycline, but not those of PMIN, was markedly changed in the presence of Ca2+. Minocycline or PMIN inhibited both phases of formalin-induced nociception and carrageenan-induced paw oedema. It is unlikely that antinociception resulted from lack of motor coordination, as tetracycline did not impair the performance of mice on the rotating rod.

CONCLUSIONS AND IMPLICATIONS

These results indicate that inhibition of nociception and oedema by tetracyclines is neither necessarily linked to antibacterial nor to Ca2+ chelating activities. This study supports the evaluation of the potential usefulness of PMIN in the treatment of painful and inflammatory diseases, as its lack of antibacterial and Ca2+ chelating activities might confer greater safety over conventional tetracyclines.

Synthesis and antioxidant activities of 3,5-dialkoxy-4-hydroxycinnamamides

A series of 3,5-dialkoxy-4-hydroxycinnamamides 6 and 7 was synthesized, and their antioxidant activity was assessed using the thiobarbituric acid reactive substance (TBARS) assay. Interestingly, cinnamamides with longer alkoxy groups on the C-3 and C-5 positions display enhanced inhibition, and most of the compounds in the series tested exhibit excellent lipid peroxidation inhibitory activities. Some cinamamides bearing hexyloxy or 2,6-di-tert-butyl-4-methyl phenol groups have submicromolar inhibitory activities.

Syntheses and biological activities of benzimidazolo[2,1-b] benzo[e]thiazepin-5(10H)-ones

Substituted benzimidazolo[2,1-b]benzo[e]thiazepin-5(10H)-one derivatives were prepared in moderate to good yield by reaction of mercapto benzimidazole derivatives with 2-chloromethylbenzoyl chloride as a coupling component. Their structures were confirmed by elemental analysis, IR, NMR, and MS. Their antioxidant properties were evaluated by several methods: scavenging effect on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals, reducing power assay, and inhibition of lipid peroxidation. In DPPH assay, 3h exhibited an activity stronger than trolox. In the reducing power assay and inhibition of lipid peroxidation, compound 3a was more active than 3h and similar to trolox. The antidiabetic effect was also determined, and the antidiabetic activities were correlated with their antioxidant properties, compound 3a was the most active compound in the in-vivo experiments.

Recent advances in MMP inhibitor design

The search for an MMP inhibitor with anticancer efficacy is a nearly three-decade endeavor. This inhibitor is yet to be found. The reasons for this failure include shortcomings in the chemistry of these compounds (including broad MMP sub-type selectivity, metabolic lability, and toxicity) as well as the emerging, and arguably extraordinary, complexity of MMP cell (and cancer) biology. Together these suggest that the successful anticancer inhibitor must possess MMP selectivity against the MMP subtype whose involvement is critical, yet highly temporally (with respect to metastatic progression) and mechanistically (with respect to matrix degradation) regulated. This review summarizes the progression of chemical structure and mechanistic thinking toward these objectives, with emphasis on the disappointment, the perseverance, and the resilient optimism that such an inhibitor is there to be discovered.