Minocycline, a classic antibiotic, exerts psychotropic effects by normalizing microglial neuroinflammation-evoked tryptophan-kynurenine pathway dysregulation in chronically stressed male mice.

The dysregulation of tryptophan-kynurenine pathway (TKP) is extensively involved in the pathophysiology of Alzheimer's disease, depression, and neurodegenerative disorders. Minocycline, a classic antibiotic, may exert psychotropic effects associated with the modulation of TKP. In this study, we examined the effects of minocycline in improving behaviour and modulating TKP components in chronically stressed male mice. Following repeated treatment with 22.5 mg/kg and 45 mg/kg minocycline for 27 days, the stressed mice particularly with higher dose displayed significant improvement on cognitive impairment, depression- and anxiety-like behaviour. Minocycline suppressed stress-induced overexpression of pro-inflammatory cytokines and restored anti-inflammatory cytokines. Chronic stress dramatically suppressed blood and prefrontal cortical levels of the primary substrate tryptophan (TRP), the neuroprotective metabolite kynurenic acid (KYNA), and KYNA/KYN ratio, but increased the intermediate kynurenine (KYN), 3-hydroxykynurenine (3-HK), KYN/TRP ratio, and the neurotoxic metabolite quinolinic acid (QUIN). Minocycline partially or completely reversed changes in these components. Minocycline also inhibited stress-induced overexpression of QUIN-related enzymes, indoleamine 2, 3-dioxygenase 1(iDO-1), kynureninase (KYNU), kynurenine 3-monooxygenase (KMO), 3-hydroxyanthranilate 3,4-dioxygenase (3-HAO), but rescued the decreased expression of kynurenine aminotransferase (KAT) in brain regions. Behavioral improvements were correlated with multiple TKP metabolites and enzymes. These results suggest that the psychotropic effects of minocycline are mainly associated with the restoration of biodistribution of the primary substrate in the brain and normalization of neuroinflammation-evoked TKP dysregulation.

Pestalotiopsis jiangsuensis sp. nov. Causing Needle Blight on Pinus massoniana in China.

Pinus massoniana Lamb. is an important, common afforestation and timber tree species in China. Species of Pestalotiopsis are well-known pathogens of needle blight. In this study, the five representative strains were isolated from needle blight from needles of Pi. massoniana in Nanjing, Jiangsu, China. Based on multi-locus phylogenetic analyses of the three genomic loci (ITS, TEF1, and TUB2), in conjunction with morphological characteristics, a new species, namely Pestalotiopsis jiangsuensis sp. nov., was described and reported. Pathogenicity tests revealed that the five representative strains of the species described above were pathogenic to Pi. massoniana. The study revealed the diversity of pathogenic species of needle blight on Pi. massoniana. This is the first report of needle blight caused by P. jiangsuensis on Pi. massoniana in China and worldwide. This provides useful information for future research on management strategies of this disease.