Temporal analysis of lipopolysaccharide-induced sickness behavior in virgin and lactating female rats

Impact of neuroinflammation on epigenetic transcriptional control of Sonic Hedgehog members in the central nervous system

Sonic Hedgehog (Shh) signaling plays a critical role during central nervous system (CNS) development, and its dysregulation leads to neurological disorders. Nevertheless, little is known about Shh signaling regulation in the adult brain. Here, we investigated the contribution of DNA methylation on the transcriptional control of Shh signaling pathway members and its basal distribution impact on the brain, as well as its modulation by inflammation. The methylation status of the promoter regions of these members and the transcriptional profile of DNA-modifying enzymes (DNA Methyltransferases - DNMTs and Tet Methylcytosine Dioxygenase - TETs) were investigated in a murine model of neuroinflammation by qPCR. We showed that, in the adult brain, methylation in the CpG promoter regions of the Shh signaling pathway members was critical to determine the endogenous differential transcriptional pattern observed between distinct brain regions. We also found that neuroinflammation differentially modulates gene expression of DNA-modifying enzymes. This study reveals the basal transcriptional profile of DNMTs and TETs enzymes in the CNS and demonstrates the effect of neuroinflammation on the transcriptional control of members of the Shh Signaling pathway in the adult brain.

Sickness Behavior Score Is Associated with Neuroinflammation and Late Behavioral Changes in Polymicrobial Sepsis Animal Model

The use of reliable scores is a constant development in critical illness. According to Sepsis-3 consensus, the use of Sequential Organ Failure Assessment (SOFA) score of 2 or more is associated with a higher mortality of sepsis patients. In experimental research, due murine animal model limitations, the use of a score systems can be an alternative to assess sepsis severity. In this work, we suggest a sickness behavior score (SBS) that uses physiological variables to assess sepsis severity and mortality. Animals were evaluated daily by the presence of six indicators of sickness behavior: temperature alteration, preference of water/sucrose, liquid intake, food intake, body weight, and movimentation. Male adult Wistar rats were evaluated daily after sepsis induction by cecal ligation and puncture (CLP) or laparotomy only (sham) for determination of SBS. Oxidative stress, IL-6, and HPA axis markers (corticosterone and adrenal gland weight) were evaluated 24 h after CLP to determine the correlation with the acute SBS and neuroinflammation. Also, BDNF and four cognitive behavioral tests were correlated with the chronic SBS, i.e., sum of 8 days after surgery. In result, septic rats presented higher SBS than sham animals. Sepsis severity markers were associated with acute and chronic SBS. Also, SBS was negative correlated with the cognitive tests. In conclusion, SBS shows to be reliable score to predict sepsis severity and mortality. The use of score system provides the analysis of global sickness behavior, beyond evaluation of each parameter individually.

Hyperprolactinemia Impaired the Effects of Lipopolysaccharide on Both Body Temperature and Sickness Behavior in Virgin Female Rats

OBJECTIVE

Previously we observed an attenuation of body temperature in lactating rats treated with lipopolysaccharide (LPS) compared with virgin saline-treated females. We proposed that high levels of prolactin (PRL) during lactation may induce this attenuation because PRL has a suppressive effect on inflammation. In the present study, we induced hyperprolactinemia in female virgin rats to investigate the effects of PRL on body temperature and sickness behavior induced by LPS.

METHODS

To induce hyperprolactinemia, female rats in the estrous phase received domperidone 3 times/day for 5 days and an LPS injection (D + LPS group). Two other groups were treated with saline solution for 5 days, and one of them received a saline injection (S + S group) and the other LPS (S + LPS group). Tympanic temperature was assessed 0, 2, 4, 6, 8, 10, 24, 48, 72, and 96 h after treatment. Body weight gain and food and water consumption were observed 24, 48, 72, and 96 h after treatment.

RESULTS

Hyperprolactinemia impaired LPS-induced hypothermia and hyperthermia phases of body temperature. Body weight gains in the S + LPS group and the D + LPS group were similar. A decrease in food consumption was observed in the D + LPS rats at 72 and 96 h compared to the S + LPS group.

CONCLUSION

Hyperprolactinemia impaired the body temperature increase induced by LPS and several signs of sickness behavior, suggesting that febrile responses to LPS can be modulated by the physiological state. These phenomena may have adaptive value for reproduction.

Lipopolysaccharide-induced sickness behavior in lactating rats decreases ultrasonic vocalizations and exacerbates immune system activity in male offspring

OBJECTIVE

The present study analyzed the effects of lipopolysaccharide (LPS) on maternal behavior during lactation and possible correlations with changes in emotional and immune responses in offspring.

METHODS

Lactating rats received 100 μg/kg LPS, and the control group received saline solution on lactation day (LD) 3. Maternal general activity and maternal behavior were observed on LD5 (i.e. the day that the peak of fever occurred). In male pups, hematological parameters and ultrasonic vocalizations (USVs) were assessed on LD5. At weaning, an additional dose of LPS (50 µg/kg, i.p.) was administered in male pups, and open-field behavior, oxidative burst and phagocytosis were evaluated.

RESULTS

A reduction in the time in which dams retrieved the pups was observed, whereas no effects on maternal aggressive behavior were found. On LD5, a reduction of the frequency of USVs was observed in pups, but no signs of inflammation were found. At weaning, an increase in immune system activity was observed, but no differences in open-field behavior were found.

CONCLUSION

These results indicate that inflammation in lactating mothers disrupted mother/pup interactions and may have produced short- and long-term effects on pup behavior as well as biological pathways that modulate inflammatory responses to bacterial endotoxin challenge in pups.