SARS-CoV-2 Infection and Possible Neonatal Neurological Outcomes: A Literature Review.

The virus responsible for COVID-19 is designated "severe acute respiratory syndrome coronavirus 2" (SARS-CoV-2), a highly transmissible and pathogenic coronavirus. Although people of all ages are susceptible to SARS-CoV-2 infection, clinical manifestations may vary with age. The response of neonates to SARS-CoV-2 infection or exposure differs from that of children and adults. Encephalitis due to viral infections in the central nervous system (CNS) and childhood multisystem inflammatory syndrome (MIS-C) are some of the possible neonatal consequences of SARS-CoV-2 infection. This review aims to verify possible neonatal neurological outcomes after SARS-CoV-2 infection. Overall, the cellular and molecular basis of the neurological sequelae of SARS-CoV-2 in neonates remains unclear, and attempts to elucidate the pathophysiology of COVID-19 involve a comparison with the mechanism of other viral diseases. There are a considerable number of case reports in the literature exploring neurological outcomes in the neonatal period. In this review, we present possible effects of SARS-CoV-2 in neonates, emphasizing the importance of monitoring this group. The mechanisms of SARS-CoV-2 entry into the CNS have not yet been fully elucidated, and the potential severity of SARS-CoV-2 infection in neonates, as well as the possible short- and long-term neurological sequelae, remain unclear.

SARS-CoV-2 Infection in Pregnant Women: Neuroimmune-Endocrine Changes at the Maternal-Fetal Interface.

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) has devastating effects on the population worldwide. Given this scenario, the extent of the impact of the disease on more vulnerable individuals, such as pregnant women, is of great concern. Although pregnancy may be a risk factor in respiratory virus infections, there are no considerable differences regarding COVID-19 severity observed between pregnant and nonpregnant women. In these circumstances, an emergent concern is the possibility of neurodevelopmental and neuropsychiatric harm for the offspring of infected mothers. Currently, there is no stronger evidence indicating vertical transmission of SARS-CoV-2; however, the exacerbated inflammatory response observed in the disease could lead to several impairments in the offspring's brain. Furthermore, in the face of historical knowledge on possible long-term consequences for the progeny's brain after infection by viruses, we must consider that this might be another deleterious facet of COVID-19. In light of neuroimmune interactions at the maternal-fetal interface, we review here the possible harmful outcomes to the offspring brains of mothers infected by SARS-CoV-2.

Inflammatory, synaptic, motor, and behavioral alterations induced by gestational sepsis on the offspring at different stages of life.

BACKGROUND: The term sepsis is used to designate a systemic condition of infection and inflammation associated with hemodynamic changes that result in organic dysfunction. Gestational sepsis can impair the development of the central nervous system and may promote permanent behavior alterations in the offspring. The aim of our work was to evaluate the effects of maternal sepsis on inflammatory cytokine levels and synaptic proteins in the hippocampus, neocortex, frontal cortex, and cerebellum of neonatal, young, and adult mice. Additionally, we analyzed the motor development, behavioral features, and cognitive impairments in neonatal, young and adult offspring. METHODS: Pregnant mice at the 14th embryonic day (E14) were intratracheally instilled with saline 0.9% solution (control group) or Klebsiella spp. (3 × 108 CFU) (sepsis group) and started on meropenem after 5 h. The offspring was sacrificed at postnatal day (P) 2, P8, P30, and P60 and samples of liver, lung, and brain were collected for TNF-α, IL-1ß, and IL-6 measurements by ELISA. Synaptophysin, PSD95, and ß-tubulin levels were analyzed by Western blot. Motor tests were performed at all analyzed ages and behavioral assessments were performed in offspring at P30 and P60. RESULTS: Gestational sepsis induces a systemic pro-inflammatory response in neonates at P2 and P8 characterized by an increase in cytokine levels. Maternal sepsis induced systemic downregulation of pro-inflammatory cytokines, while in the hippocampus, neocortex, frontal cortex, and cerebellum an inflammatory response was detected. These changes in the brain immunity were accompanied by a reduction of synaptophysin and PSD95 levels in the hippocampus, neocortex, frontal cortex, and cerebellum, in all ages. Behavioral tests demonstrated motor impairment in neonates, and depressive-like behavior, fear-conditioned memory, and learning impairments in animals at P30 and P60, while spatial memory abilities were affected only at P60, indicating that gestational sepsis not only induces an inflammatory response in neonatal mouse brains, but also affects neurodevelopment, and leads to a plethora of behavioral alterations and cognitive impairments in the offspring. CONCLUSION: These data suggest that maternal sepsis may be causatively related to the development of depression, learning, and memory impairments in the litter.

IGF-1 and IGF-1R modulate the effects of IL-4 on retinal ganglion cells survival: The involvement of M1 muscarinic receptor.

Trophic factors are involved in different cellular responses. Previously we demonstrated that IL-4 treatment induces an increase in retinal ganglion cell survival (RGCS) and regulates cholinergic differentiation of retinal cells in vitro. Data from literature show that IGF-1 also promotes RGCS, an effect mediated by PI-3K/AKT pathway. The aim of this study was to investigate the role of IGF-1 and IGF-1R on RGCS mediated by IL-4 treatment and the role of M1 acetylcholine receptors in this effect. Here we show that the effect of IL-4 on RGCS depends on IGF-1 and IGF-1R activation, the PI-3K/AKT and NFkB intracellular pathways and depends on M1 mAChRs activation. IGF-1 increases the levels of M1 mAChRs in 15min, 45min, 24 h and 48 h in mixed retinal cells culture, modulates the levels of IL-4, pIGF-1R, IGF-1R. IL-4 modulates IGF-1, pIGF-1R and IGF-1R levels in different time intervals. These results put in evidence a crosstalk between IL-4 and IGF-1 and a role of M1 mAChRs, IGF-1 and IGF-1R in RGCS mediated by IL-4.

PKC delta activation increases neonatal rat retinal cells survival in vitro: Involvement of neurotrophins and M1 muscarinic receptors.

Protein kinase C (PKC) is a family of serine/threonine kinases related to several phenomena as cell proliferation, differentiation and survival. Our previous data demonstrated that treatment of axotomized neonatal rat retinal cell cultures for 48 h with phorbol 12-myristate 13-acetate (PMA), a PKC activator, increases retinal ganglion cells (RGCs) survival. Moreover, this treatment decreases M1 receptors (M1R) and modulates BDNF levels. The aim of this work was to assess the possible involvement of neurotrophins BDNF and NGF in the modulation of M1R levels induced by PKC activation, and its involvement on RGCs survival. Our results show that PMA (50 ng/mL) treatment, via PKC delta activation, modulates NGF, BDNF and M1R levels. BDNF and NGF mediate the decrease of M1R levels induced by PMA treatment. M1R activation is essential to PMA neuroprotective effect on RGCs as telenzepine (M1R selective antagonist) abolished it. Based on our results we suggest that PKC delta activation modulates neurotrophins levels by a signaling pathway that involves M1R activation and ultimately leading to an increase in RGCs survival in vitro.

The trophic effect of ouabain on retinal ganglion cells is mediated by IL-1ß and TNF-α.

Ouabain is a steroid hormone that binds to the enzyme Na(+), K(+) - ATPase and stimulates different intracellular pathways controlling growth, proliferation and cell survival. IL-1ß and TNF-α are pleiotropic molecules, conventionally regarded as pro-inflammatory cytokines with well-known effects in the immune system. In addition, IL-1ß and TNF-α also play important roles in the nervous system including neuroprotective effects. Previous data from our group showed that ouabain treatment is able to induce an increase in retinal ganglion cell survival kept in mixed retinal cell cultures. The aim of this work was to investigate if IL-1ß and TNF-α could be mediating the trophic effect of ouabain on retinal ganglion cells. Our results show that the trophic effect of ouabain on retinal ganglion cell was inhibited by either anti-IL-1ß or anti-TNF-α antibodies. In agreement, IL-1ß or TNF-α increased the retinal ganglion cells survival in a dose-dependent manner. Accordingly, ouabain treatment induces a temporal release of TNF-α and IL-1ß from retinal cell cultures. Interestingly, TNF-α and IL-1ß regulate each other intracellular levels. Our results suggest that ouabain treatment triggers the activation of TNF-α and IL-1ß signaling pathways leading to an increase in retinal ganglion cell survival.

IL-4 Induces Cholinergic Differentiation of Retinal Cells In Vitro.

Interleukin-4 (IL-4) is a pleiotropic cytokine that regulates several phenomena, among them survival and differentiation of neuronal and glial cells. The aim of this work was to investigate the effect of IL-4 on the cholinergic differentiation of neonatal rat retinal cells in vitro, evaluating its effect on the levels of cholinergic markers (CHT1-high-affinity choline transporter; VAChT-vesicular acetylcholine transporter, ChAT-choline acetyltransferase, AChE-acetylcholinesterase), muscarinic receptors, and on the signaling pathways involved. Lister Hooded rat pups were used in postnatal days 0-2 (P0-P2). Our results show that IL-4 treatment (50 U/mL) for 48 h increases the levels of the cholinergic transporters VAChT and CHT1, the acetylcholinesterase activity, and the number of ChAT-positive cells. It also induces changes in muscarinic receptor levels, leading to a small decrease in M1 levels and a significant increase in M3 and M5 levels after 48 h of treatment. We also showed that IL-4 effect on M3 receptors is dependent on type I IL-4 receptor and on an increase in NFκB phosphorylation. These results indicate that IL-4 stimulates cholinergic differentiation of retinal cells.

PMA increases M3 muscarinic receptor levels and decreases retinal cells proliferation through a change in the levels of cell-cycle regulatory proteins.

Protein kinase C (PKC) pathway plays important roles in different phenomena in nervous system development. Our previous data demonstrated that phorbol 12-myristate 13-acetate (PMA) treatment, a PKC activator, for 48 h decreases retinal cells proliferation by a mechanism mediated by muscarinic receptor activation, involving a decrease in M1 receptors levels. The aim of this work was to analyze how PMA interferes in the levels of cell cycle control proteins p53, p21 and cyclin D1 and also to investigate its influence on M3 receptor levels. Our results show that PMA (50 ng/mL) produces a significant increase in p21 and p53 levels, decreases cyclin D1 levels, and also enhances M3 receptors levels in cell cultures. Evaluating the postnatal retinal tissue development until 30 days, we observed that tissue differentiation is accompanied by an increase in M3 and p21 levels. Based on our results we suggest that PMA treatment is promoting a change in muscarinic receptors expression mimicking the pattern observed during tissue differentiation, indicating that PMA is probably accelerating the cholinergic differentiation in rat retinal cell cultures.