Ureaplasma-Driven Neonatal Neuroinflammation: Novel Insights from an Ovine Model

Abstract

Ureaplasma species (spp.) are considered commensals of the adult genitourinary tract, but have been associated with chorioamnionitis, preterm birth, and invasive infections in neonates, including meningitis. Data on mechanisms involved in Ureaplasma-driven neuroinflammation are scarce. The present study addressed brain inflammatory responses in preterm lambs exposed to Ureaplasma parvum (UP) in utero. 7 days after intra-amniotic injection of UP (n = 10) or saline (n = 11), lambs were surgically delivered at gestational day 128-129. Expression of inflammatory markers was assessed in different brain regions using qRT-PCR and in cerebrospinal fluid (CSF) by multiplex immunoassay. CSF was analyzed for UP presence using ureB-based real-time PCR, and MRI scans documented cerebral white matter area and cortical folding. Cerebral tissue levels of atypical chemokine receptor (ACKR) 3, caspases 1-like, 2, 7, and C-X-C chemokine receptor (CXCR) 4 mRNA, as well as CSF interleukin-8 protein concentrations were significantly increased in UP-exposed lambs. UP presence in CSF was confirmed in one animal. Cortical folding and white matter area did not differ among groups. The present study confirms a role of caspases and the transmembrane receptors ACKR3 and CXCR4 in Ureaplasma-driven neuroinflammation. Enhanced caspase 1-like, 2, and 7 expression may reflect cell death. Increased ACKR3 and CXCR4 expression has been associated with inflammatory central nervous system (CNS) diseases and impaired blood-brain barrier function. According to these data and previous in vitro findings from our group, we speculate that Ureaplasma-induced caspase and receptor responses affect CNS barrier properties and thus facilitate neuroinflammation.

Keywords: Animal model; CNS Integrity; Immaturity; Neonatal meningitis; Preterm birth; Ureaplasma parvum.

Fig. 1

MRI scans were used to assess a potential influence of prenatal U. parvum exposure on cortical folding (a, sagittal plane) and brain white matter area (b, coronal plane). Results are presented in scatter plots showing means ± SD, comparing the control group (n = 5) and the group exposed to U. parvum (UP, n = 4). The animal with a positive CSF Ureaplasma PCR is marked in red

Fig. 2

Brain tissue mRNA expression of ACKR3, caspase (CASP) 1-like, CASP2, CASP3, CASP7, CASP9, CXCR 4, ICAM-1, VCAM-1, and VEGF was assessed for BFC and BPZ. Scatter plots present individual data points as well as means ± SD. U. parvum-exposed animals (UP, n = 10) were compared to control animals (n = 5). The animal tested positive for UP is marked in red. *p < 0.05, **p < 0.01 vs. control

Fig. 3

CSF protein concentrations of IFN-γ, IL-1α, IL-6, IL-8, IL-10, IL-17A, IL-36 RA, IP-10, MCP-1, MIP-1α, TNF, and VEGF depict responses to Ureaplasma exposure of fetal lambs (UP, n = 5) compared to control animals (n = 5). The CSF Ureaplasma-positive animal is marked in red. Data are shown as means ± SD, *p < 0.05 vs. control

Fig. 4

Scatter plots present somatic parameters itemized for the individual animals as well as means ± SD (please refer to Table 1 for n). The single animal with a positive CSF Ureaplasma PCR is marked in red