Communication of gut microbiota and brain via immune and neuroendocrine signaling

The gastrointestinal tract of the human is inhabited by about 5 × 10¹³ bacteria (of about 1,000 species) as well as archaea, fungi, and viruses. Gut microbiota is known to influence the host organism, but the host may also affect the functioning of the microbiota. This bidirectional cooperation occurs in three main inter-organ signaling: immune, neural, and endocrine. Immune communication relies mostly on the cytokines released by the immune cells into circulation. Also, pathogen-associated or damage-associated molecular patterns (PAMPs or DAMPs) may enter circulation and affect the functioning of the internal organs and gut microbiota. Neural communication relies mostly on the direct anatomical connections made by the vagus nerve, or indirect connections via the enteric nervous system. The third pathway, endocrine communication, is the broadest one and includes the hypothalamic-pituitary-adrenal axis. This review focuses on presenting the latest data on the role of the gut microbiota in inter-organ communication with particular emphasis on the role of neurotransmitters (catecholamines, serotonin, gamma-aminobutyric acid), intestinal peptides (cholecystokinin, peptide YY, and glucagon-like peptide 1), and bacterial metabolites (short-chain fatty acids).

The Anti-Inflammatory Effect of Cabbage Leaves Explained by the Influence of bol-miRNA172a on FAN Expression

Recently, the possibility of cross-kingdom gene expression regulation by miRNAs from other species (“xenomiRs”), specifically from plants, has acquired scientific meaning. Based on the one of oldest methods for dealing with inflammation via the use of cabbage leaf compresses, we investigated the effects of Brassica oleracea derived miR172a on the potential human target gene encoding FAN (Factor Associated with Neutral Sphingomyelinase Activation) protein. In vitro experiments showed a decrease in FAN protein levels in both human and mouse cells transfected with bol-miRNA172a. As the FAN protein mediates inflammatory responses, the potential of miR172a to mitigate the inflammatory process was tested in a mouse model of rheumatoid arthritis. Animal studies showed the decreased oedema of inflamed paws in mouse with rheumatoid arthritis model induced after treatment with miR172a.

Anti-CD52 Therapy for Multiple Sclerosis: An Update in the COVID Era

CD52 is a small surface glycoprotein composed of 12 amino acids. CD52 is found mostly on the surface of mature immune cells, such as lymphocytes, monocytes, eosinophils, and dendritic cells, as well as the male genital tract: within the epididymis and on the surface of mature sperm. Low CD52 expression is also found in neutrophils. CD52 function is not fully understood, although experiments with anti-CD52 antibodies have shown that CD52 is essential for lymphocyte transendothelial migration and may contribute to costimulation of CD4⁺ T cells and T-cell activation and proliferation. Although knowledge about exact CD52 function is still poor, CD52 presence on the surface of a broad spectrum of immune cells makes it a therapeutic target, especially in immunomediated diseases, such as multiple sclerosis. In multiple sclerosis, alemtuzumab is registered for adult patients with the relapsing–remitting form of the disease defined by clinical and imaging features. Despite the high efficacy of the drug, the main issue is its safety. The main adverse effects of alemtuzumab are associated with drug infusion due to cytokine release and cytotoxic effects of antibodies associated with lymphocyte depletion, which leads to immunosuppression, and secondary autoimmunity that may be the effect of excessive B-cell repopulation and cancer. This review presents current knowledge on the drug’s mechanism of action, efficacy and safety data from clinical trials, and real-world observations, including available though scarce data on using alemtuzumab in the COVID era.

The Positive and Negative Outcome of Morphine and Disulfiram Subacute Co-Administration in Rats in the Absence of Ethanol Challenge

Recently, a well-known anti-alcohol agent, disulfiram (DSF), has gain much interest, as it was found to be effective in the treatment of cocaine abusers, thus also giving hope for patients addicted to opioids and other illicit drugs. Therefore, this study was aimed to investigate the possible outcome that might occur within the subacute co-administration of both morphine (MRF) and DSF in rats, but in the absence of ethanol challenge. As observed, intraperitoneal DSF dose-dependently enhanced MRF-mediated analgesia with the maximal efficacy at a dose of 100 mg/kg. Furthermore, MRF-induced tolerance and aggressive behavior were significantly reduced by DSF (100 mg/kg, i.p.) in comparison to MRF solely. Nonetheless, significant blood biochemical markers of hepatotoxicity were found (i.e., alteration in the levels of glutathione, blood urea nitrogen, etc.), following a combination of both drugs. Likewise, histological analysis of liver tissue revealed severe changes in the group of DSF + MRF, which includes swelling, cell death, damage to certain vessels, and hemorrhages into the liver parenchyma. Our findings indicate that DSF should be used with extreme caution, especially within the course of subacute concomitant use with MRF, as several possible side effects may take place.

Novel opioid-neurotensin-based hybrid peptide with spinal long-lasting antinociceptive activity and a propensity to delay tolerance development

The behavioral responses exerted by spinal administration of the opioid-neurotensin hybrid peptide, PK23, were studied in adult male rats. The antinociceptive effect upon exposure to a thermal stimulus, as well as tolerance development, was assessed in an acute pain model. The PK23 chimera at a dose of 10 nmol/rat produced a potent pain-relieving effect, especially after its intrathecal administration. Compared with intrathecal morphine, this novel compound was found to possess a favourable side effect profile characterized by a reduced scratch reflex, delayed development of analgesic tolerance or an absence of motor impairments when given in the same manner, though some animals died following barrel rotation as a result of its i.c.v. administration (in particular at doses higher than 10 nmol/rat). Nonetheless, these results suggest the potential use of hybrid compounds encompassing both opioid and neurotensin structural fragments in pain management. This highlights the enormous potential of synthetic neurotensin analogues as promising future analgesics.

Common Genetic Variants Link the Abnormalities in the Gut-Brain Axis in Prematurity and Autism

This review considers a link between prematurity and autism by comparing symptoms, physiological abnormalities, and behavior. It focuses on the bidirectional signaling between the microbiota and the brain, here defined as the microbiota-gut-vagus-heart-brain (MGVHB) axis and its systemic disruption accompanying altered neurodevelopment. Data derived from clinical and animal studies document increased prevalence of gastrointestinal, cardiovascular, cognitive, and behavioral symptoms in both premature and autistic children and suggest an incomplete maturation of the gut-blood barrier resulting in a “leaky gut,” dysbiosis, abnormalities in vagal regulation of the heart, altered development of specific brain regions, and behavior. Furthermore, this review posits the hypothesis that common genetic variants link the abnormalities in the MGVHB axis in premature and autistic pathologies. This hypothesis is based on the recently identified common genetic variants: early B cell factor 1 (EBF1), selenocysteine tRNA-specific eukaryotic elongation factor (EEFSEC), and angiotensin II receptor type 2 (AGTR2), in the maternal and infant DNA samples, associated with risk of preterm birth and independently implicated in a risk of autism. We predict that the AGTR2 variants involved in the brain maturation and oxytocin-arginine-vasopressin (OXT-AVP) pathways, related to social behavior, will contribute to our understanding of the link between prematurity and autism paving a way to new therapies.

A rat model to study maternal depression during pregnancy and postpartum periods, its comorbidity with cardiovascular diseases and neurodevelopmental impact in the offspring

This study aimed to develop an animal model of human depression during pregnancy and lactation to examine the effect of maternal, perinatal depression on offspring development. Maternal depression during pregnancy affects up to 20% of women and is a risk factor for both the developmental and long-term health issues. It is often comorbid with the cardiovascular disease (CVD) that affects the uteroplacental circulation and impacts offspring development. More than half of the expecting mothers with depression use antidepressants that cross the placenta and may interfere with the neurodevelopmental programming. Thus, depressed pregnant mothers face a difficult choice whether "to use or not to use" antidepressant therapy, since both untreated depression and antenatal antidepressant exposure present increased risks of neurodevelopmental pathologies. The ongoing clinical debate presents inconclusive data, while the existing animal models of maternal depression do not include early gestational periods, and, do not monitor depressive-like behavior nor address the cardiovascular abnormalities. The presented model includes pregestational depressive behavior extending into pregnancy and lactation, periods that have not been previously examined. Rat dams exposed to pre-gestational chronic mild stress (CMS) developed a sustained decrease in self-grooming behavior, correlated with hormonal, behavioral, and cardiac changes persisting through the postpartum period. Preliminary data indicate neurodevelopmental delays, behavioral and cardiac abnormalities, and altered levels of both the brain and the heart markers in the offspring of stressed dams. Furthermore, the preliminary data predict that maternal pregnancy during the perinatal period is likely to impact the neurodevelopmental process in a sex-dependent manner. Thus the presented here model (PG-LAC CMS) fulfills both the face and the construct validity criteria for maternal stress-induced depression during pregnancy and postpartum that may facilitate further studies of the relative risks of untreated vs. antidepressant-treated maternal depression during pregnancy to the mother and her offspring.

Modulation of 22-khz postejaculatory vocalizations by conditioning to new place: Evidence for expression of a positive emotional state

It has been assumed that the 22-kHz ultrasonic vocalizations (USVs) are emitted by adult rats as a result of a negative emotional state. However, emission of the 22-kHz vocalizations by male rats has been also observed following ejaculation, which has a high rewarding value as shown by a conditioned place preference test. These observations suggest that 22-kHz USVs may also occur in response to a positive emotional state. The aim of this study was to determine whether the postejaculatory 22-kHz USVs are related to conditioning processes. The 22 kHz USVs were recorded in Sprague-Dawley males in the postejaculatory refractory period during conditioning processes to a new chamber unrelated to copulation. During the first session in the clean recording chamber, males vocalized marginally and exhibited intensive rearing behavior. From the second to fourth sessions, vocalization duration increased and the number of rearing decreased. Following established conditioning process, odor cues from foreign males, but not the familiar ones, resulted in decreased duration of 22-kHz USVs and increased the number of rearing. On the other hand, in the presence of mating cues (copulatory chamber and presence of the female), males exhibited increased duration of postejaculatory 22-kHz USVs and reduced number of rearing. These results demonstrated that the conditioning to the cues, both unrelated and related to copulation, is important for evoking postejaculatory 22-kHz USVs as well as the relaxation state. Furthermore, these results confirmed the postejaculatory 22-kHz USVs' involvement in expression of the positive emotional state. (PsycINFO Database Record

Oral Administration of Lactococcus lactis Expressing Synthetic Genes of Myelin Antigens in Decreasing Experimental Autoimmune Encephalomyelitis in Rats

Background

Multiple sclerosis is a human autoimmunological disease that causes neurodegeneration. One of the potential ways to stop its development is induction of oral tolerance, whose effect lies in decreasing immune response to the fed antigen. It was shown in animal models that administration of specific epitopes of the three main myelin proteins – myelin oligodendrocyte glycoprotein (MOG), myelin basic protein (MBP), and proteolipid protein (PLP) – results in induction of oral tolerance and suppression of disease symptoms. Use of bacterial cells to produce and deliver antigens to gut mucosa seems to be an attractive method for oral tolerance induction in treatment of diseases with autoimmune background.

Material/Methods

Synthetic genes of MOG35-55, MBP85-97, and PLP139-151 myelin epitopes were generated and cloned in Lactococcus lactis under a CcpA-regulated promoter. The tolerogenic effect of bacterial preparations was tested on experimental autoimmune encephalomyelitis, which is the animal model of MS. EAE was induced in rats by intradermal injection of guinea pig spinal cord homogenate into hind paws.

Results

Rats were administered preparations containing whole-cell lysates of L. lactis producing myelin antigens using different feeding schemes. Our study demonstrates that 20-fold, but not 4-fold, intragastric administration of autoantigen-expressing L. lactis cells under specific conditions reduces the clinical symptoms of EAE in rats.

Conclusions

The present study evaluated the use of myelin antigens produced in L. lactis in inhibiting the onset of experimental autoimmune encephalomyelitis in rats. Obtained results indicate that application of such recombinant cells can be an attractive method of oral tolerance induction.

Spinal cord hydrolysate ameliorate immunological reaction in experimental allergic encephalomyelitis

The aim of this study was to use the hydrolysate of pig spinal cord proteins to induce oral tolerance in the animal model of sclerosis multiplex - experimental allergic encephalomyelitis. The female Lewis rats were fed with hydrolysate of pig spinal cord proteins in two doses for one week before immunization, which was induced by injection of guinea pig spinal cord homogenate. At the peak of clinical symptoms (the 13th day post immunization) the rats were sacrificed and the spleen removed. Splenocytes were suspended in a culture medium and placed in microculture plates. The cells were stimulated with homogenate. The cells were cultured for seven days. Proliferation of splenocytes was estimated by means of methyl-3H thymidine incorporation. In supernatants of cultures of splenocytes the level of cytokines INF-gamma, IL-10, IL-4, and TGF-gamma was measured. It was demonstrated that homogenate-induced splenocytes of hydrolysate-fed rats gave rise to low proliferation as compared to the controls used. The IFN-gamma was inhibited in hydrolysate-fed animals. The hydrolysate of pig spinal cord proteins has a modulatory effect on the immune reaction, particularly on the orally-induced antigen-specific modulation of autoimmune response.