Mechanism of Escherichia coli Resistance to Pyrrhocoricin

Due to their lack of toxicity to mammalian cells and good serum stability, proline-rich antimicrobial peptides (PR-AMPs) have been proposed as promising candidates for the treatment of infections caused by antimicrobial-resistant bacterial pathogens. It has been hypothesized that these peptides act on multiple targets within bacterial cells, and therefore the likelihood of the emergence of resistance was considered to be low. Here, we show that spontaneous Escherichia coli mutants resistant to pyrrhocoricin arise at a frequency of approximately 6 × 10⁻⁷. Multiple independently derived mutants all contained a deletion in a nonessential gene that encodes the putative peptide uptake permease SbmA. Sensitivity could be restored to the mutants by complementation with an intact copy of the sbmA gene. These findings question the viability of the development of insect PR-AMPs as antimicrobials.     

Ophthalmological injuries associated with fractures of the orbitozygomaticomaxillary complex

Our aim was to evaluate ophthalmological injuries associated with fractures of the orbitozygomaticomaxillary complex that required operative treatment, and we collected data retrospectively over a period of five years (2012-2016 inclusive). Of the 190 patients, 162 were male with a median age of 31 (IQR 25 -39) years. Assault was the most common mechanism of injury (125/190, 66%). Minor ophthalmic injuries (those unlikely to cause permanent visual disturbance) and major ophthalmic injuries (those with the potential to cause permanent visual disturbance) were recorded. The common minor ophthalmic injuries were: diplopia, enophthalmos, proptosis, subconjunctival haemorrhage, and restriction of the extraocular muscles. Commotio retinae, traumatic mydriasis, retro-orbital haemorrhage, and hyphaema were the common major ophthalmic injuries. All 13 different major ophthalmic injuries were recorded in the group who had had orbital fractures reconstructed, which suggested that more intraocular damage can be caused by this type of fracture than by others. Visual acuity was reduced in 26/190 patients with only four having persistent postoperative changes at six weeks. The odds ratio for those patients who had a major ophthalmological injury and were unable to drive was 0.07 (95% CI 0.02 to 0.21, p = 0.001), which was highly significant. Ophthalmological assessment is strongly recommended for patients with fractures of the orbitozygomaticomaxillary complex.     

Prefrontal D1 dopamine signaling is required for temporal control

Temporal control, or how organisms guide movements in time to achieve behavioral goals, depends on dopamine signaling. The medial prefrontal cortex controls many goal-directed behaviors and receives dopaminergic input primarily from the midbrain ventral tegmental area. However, this system has never been linked with temporal control. Here, we test the hypothesis that dopaminergic projections from the ventral tegmental area to the prefrontal cortex influence temporal control. Rodents were trained to perform a fixed-interval timing task with an interval of 20 s. We report several results: first, that decreasing dopaminergic neurotransmission using virally mediated RNA interference of tyrosine hydroxylase impaired temporal control, and second that pharmacological disruption of prefrontal D1 dopamine receptors, but not D2 dopamine receptors, impaired temporal control. We then used optogenetics to specifically and selectively manipulate prefrontal neurons expressing D1 dopamine receptors during fixed-interval timing performance. Selective inhibition of D1-expressing prefrontal neurons impaired fixed-interval timing, whereas stimulation made animals more efficient during task performance. These data provide evidence that ventral tegmental dopaminergic projections to the prefrontal cortex influence temporal control via D1 receptors. The results identify a critical circuit for temporal control of behavior that could serve as a target for the treatment of dopaminergic diseases.     

4-Hydroxynonenal regulates mitochondrial function in human small airway epithelial cells

Prolonged exposure to oxidative stress causes Acute Lung Injury (ALI) and significantly impairs pulmonary function. Previously we have demonstrated that mitochondrial dysfunction is a key pathological factor in hyperoxic ALI. While it is known that hyperoxia induces the production of stable, but toxic 4-hydroxynonenal (4-HNE) molecule, it is unknown how the reactive aldehyde disrupts mitochondrial function. Our previous in vivo study indicated that exposure to hyperoxia significantly increases 4-HNE-Protein adducts, as well as levels of MDA in total lung homogenates. Based on the in vivo studies, we explored the effects of 4-HNE in human small airway epithelial cells (SAECs). Human SAECs treated with 25 μM of 4-HNE showed a significant decrease in cellular viability and increased caspase-3 activity. Moreover, 4-HNE treated SAECs showed impaired mitochondrial function and energy production indicated by reduced ATP levels, mitochondrial membrane potential, and aconitase activity. This was followed by a significant decrease in mitochondrial oxygen consumption and depletion of the reserve capacity. The direct effect of 4-HNE on the mitochondrial respiratory chain was confirmed using Rotenone. Furthermore, SAECs treated with 25 μM 4-HNE showed a time-dependent depletion of total Thioredoxin (Trx) proteins and Trx activity. Taken together, our results indicate that 4-HNE induces cellular and mitochondrial dysfunction in human SAECs, leading to an impaired endogenous antioxidant response.