Anxiolytic activity of the neuroprotective peptide HLDF-6 and its effects on brain neurotransmitter systems in BALB/c and C57BL/6 mice

HLDF-6 peptides exhibit neuroprotective effects in the experimental model of preclinical Parkinson's disease

The mechanisms of the neuroprotective action of the hexapeptides HLDF-6 encoded by the amino acid sequence 41-46 of Human Leukemia Differentiation Factor and its homoserine derivative HLDF-6H were studied in an experimental 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced model of Parkinson's disease (PD). C57Bl/6 mice received two intraperitoneal injections of 18 mg/kg MPTP-HCl, with an interval of 2 hours. MPTP-induced motor dysfunction was assessed using horizontal grid test. Our data show that chronic intranasal administration of peptides (3 weeks, 300 μg/kg/day) restored normal levels of dopamine and improved its turnover rates in the striatum. Furthermore, peptide administration increased serum estradiol levels and led to a significant improvement in motor functions in MPTP-treated mice. Additionally, peptide treatment increased the levels of mRNA encoding neurotrophin BDNF, but normalized the levels of mRNA encoding the inflammatory mediators TGFβ1, IL1β and IFNγ in the brain. Collectively, our behavioral and biochemical studies demonstrate that HLDF-6 peptides have a therapeutic potential for treating PD. We propose that HLDF-6 peptides may exert their neuroprotective mechanism, at least in part, by normalizing estradiol levels and modulating the expression of key factors involved in neurotrophic support and neuroinflammation.

Neurotropic peptide HLDF-6-amide reduces age-related decline in sexual activity in old male rats

Aging is associated with a decline in the erectile capacity and sexual motivation. Emerging new therapy for the treatment of these age-related pathologies in men is the use of the regulatory peptides. We validated the use of HLDF-6-amide (Thr-Gly-Glu-Hse-His-Arg-NH2) as a potential modulator of sexual performance in aged male rats. Behavioral tests, including the standard parameters of sexual behavior, were performed longitudinally at 20 and 26 months of age. The effects of HLDF-6-amide administered daily at 300 μg/kg for 3 week on the levels of sex hormones and the activity of antioxidant enzymes and indicators of inflammation were evaluated. HLDF-6-amide administration increased the copulative activity of the 20-month-old male rats. This effect of HLDF-6-amide was more pronounced in the 26-month-old rats. Although HLDF-6-amide did not have the effect on the levels of circulating testosterone and estradiol, it reduced the activity of leukocyte elastase and glutathione-S-peroxidase, suggesting that the peptide has anti-inflammatory and antioxidant properties. Therefore, this study shows that HLDF-6-amide has the positive impact on sexual activity in this rodent model, representing a new therapeutic approach for improving sexual performance in older men.

Long-lasting monoaminergic and behavioral dysfunctions in a mice model of socio-environmental stress during adolescence

Adolescence is one of the critical periods of development and has great importance to health for an individual as an adult. Stressors or traumatic events during this period are associated with several psychiatric disorders as related to anxiety or depression and cognitive impairments, but whether negative experiences continue to hinder individuals as they age is not as well understood. We determined how stress during adolescence affects behavior and neurochemistry in adulthood. Using an unpredictable paradigm (2 stressors per day for 10days) in Balb/c mice, behavioral, hormonal, and neurochemical changes were identified 20days after the cessation of treatment. Adolescent stress increased motor activity, emotional arousal and vigilance, together with a reduction in anxiety, and also affected recognition memory. Furthermore, decreased serotonergic activity on hippocampus, hypothalamus and cortex, decreased noradrenergic activity on hippocampus and hypothalamus, and increased the turnover of dopamine in cortex. These data suggest behavioral phenotypes associated with emotional arousal, but not depression, emerge after cessation of stress and remain in adulthood. Social-environmental stress can induce marked and long-lasting changes in HPA resulting from monoaminergic neurotransmission, mainly 5-HT activity.