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One bout of neonatal inflammation impairs adult respiratory motor plasticity in male and female rats

  1. Austin D Hocker
  2. Sarah A Beyeler
  3. Alyssa N Gardner
  4. Stephen M Johnson
  5. Jyoti J Watters
  6. Adrianne G Huxtable  Is a corresponding author
  1. University of Oregon, United States
  2. University of Wisconsin-Madison, United States
Research Article
Cite this article as: eLife 2019;8:e45399 doi: 10.7554/eLife.45399
8 figures, 3 tables and 1 additional file

Figures

Neonatal inflammation increases mortality in neonatal males and transiently delays weight gain in male and female rats.

After neonatal inflammation (P4, LPS 1 mg/kg, i.p.) male mortality (A) is increased within 24 hr (Fisher’s exact test, p = 0.006), but not in females (p = 0.466), relative to saline controls. Weekly male and female weights (B) after neonatal saline or LPS. (*p < 0.05, significant pairwise difference within sex).

https://doi.org/10.7554/eLife.45399.003
Neonatal systemic inflammation undermines adult, Q-pathway-evoked pLTF in male and female rats.

Representative integrated phrenic neurograms from male (A) and female rats (B) after neonatal (P4) saline (top traces, black) or LPS (1 mg/kg, i.p.; bottom traces, grey). Q-pathway-evoked pLTF is evident in adults after neonatal saline as the progressive increase in phrenic nerve amplitude from baseline (dashed line) over 60 min following moderate acute intermittent hypoxia (mAIH, 3 × 5 min episodes, PaO235–45 mmHg). Group data (C) demonstrate Q-pathway-evoked pLTF 60 min after mAIH is abolished in adults by neonatal LPS in both males (circles) and females (triangles) and no change in phrenic amplitude in time controls (**p < 0.01, ***p < 0.001 from baseline, # p < 0.05, ### p < 0.001 between groups, ‡ p < 0.05 from adult males and females after neonatal saline).

https://doi.org/10.7554/eLife.45399.005
Acute, adult anti-inflammatory (ketoprofen, Keto) restores Q-pathway-evoked pLTF after neonatal systemic inflammation in adult male and female rats.

Representative integrated phrenic neurograms for adult male (A) and female (B) rats after neonatal (P4) saline (top traces, black) or LPS (1 mg/kg, i.p.; bottom traces, grey) and acute, adult ketoprofen (12.5 mg/kg, i.p., 3 hr). Q-pathway-evoked pLTF is evident as the progressive increase in phrenic nerve amplitude from baseline (black dashed line) over 60 min following moderate acute intermittent hypoxia (mAIH, 3 × 5 min episodes, PaO235–45 mmHg). Group data (C) demonstrate adult ketoprofen restores Q-pathway-evoked pLTF 60 min after mAIH in adults after neonatal LPS in both males (circles) and females (triangles) and no change in phrenic amplitude in time controls (***p < 0.001 from baseline, ‡ p < 0.05 from all other groups).

https://doi.org/10.7554/eLife.45399.007
Neonatal inflammation does not increase adult medullary or spinal inflammatory gene expression.

Homogenate samples isolated from adult medullas showed no significant increase in inflammatory mRNA after neonatal inflammation (A). Similarly, homogenate samples from isolated adult cervical spinal cords (B) were not increased by neonatal inflammation, but COX2 gene expression was significantly decreased in adults after neonatal inflammation (*p < 0.05).

https://doi.org/10.7554/eLife.45399.009
Neonatal systemic inflammation undermines adult, S-pathway-evoked pLTF in male and female rats.

Representative integrated phrenic neurograms for adult male (A) and female (B) rats after neonatal (P4) saline (top traces, black) or LPS (1 mg/kg, i.p.; bottom traces, grey). S-pathway-evoked pLTF is evident as the progressive increase in phrenic nerve amplitude from baseline (black dashed line) over 60 min following severe acute intermittent hypoxia (sAIH, 3 × 5 min episodes, PaO225–35 mmHg) in adults after neonatal saline. Group data (C) demonstrate S-pathway-evoked pLTF 60 min after sAIH is abolished in adults by neonatal LPS in both males (circles) and females (triangles) and no change in phrenic amplitude in time controls (**p < 0.01, ***p < 0.001 from baseline ## p < 0.01, ### p < 0.001 between groups, ‡ p < 0.05 from male and female adults after neonatal saline).

https://doi.org/10.7554/eLife.45399.011
Adult, anti-inflammatory (ketoprofen, keto) does not restore S-pathway-evoked pLTF after neonatal systemic inflammation in adult male and female rats.

Representative integrated phrenic neurograms for adult male (A) and female (B) rats after neonatal (P4) saline (top traces, black) or LPS (1 mg/kg, i.p.; bottom traces, grey) and acute, adult ketoprofen (12.5 mg/kg, i.p., 3 hr). S-pathway-evoked pLTF is evident as the progressive increase in phrenic nerve amplitude from baseline (black dashed line) over 60 min following severe acute intermittent hypoxia (sAIH, 3 × 5 min episodes, PaO235–45 mmHg) in adults after neonatal saline. Group data (C) demonstrate acute, adult ketoprofen does not restore S-pathway-evoked pLTF 60 min after sAIH after neonatal LPS in adult males (circles) and females (triangles) and no change in phrenic amplitude in time controls (**p < 0.01, ***p < 0.001 from baseline, ## p < 0.01, ### p < 0.001 between groups, ‡ p < 0.05 from adult males and females after neonatal saline).

https://doi.org/10.7554/eLife.45399.013
Intermittent adult, adenosine receptor agonism reveals plasticity after neonatal systemic inflammation in male and female rats.

Representative integrated phrenic neurograms for adult male (A) and female (B) rats after neonatal (P4) saline (top traces, black) or LPS (1 mg/kg, i.p.; bottom traces, grey). S-pathway-evoked phrenic motor plasticity is evident as the progressive increase in phrenic nerve amplitude from baseline (black dashed line) 90 min following intermittent CGS-21680 (100 µM, black arrows, 3 × 5 min apart) in adults after neonatal saline. Group data (C) demonstrate adult CGS-21680 reveals S-pathway-evoked plasticity after neonatal LPS in adult males (circles) and females (triangles) and no change in phrenic amplitude in vehicle controls (***p < 0.001 from baseline, ‡ p < 0.001 from adult males and females after neonatal saline).

https://doi.org/10.7554/eLife.45399.015
Neonatal inflammation does not alter GFAP or IBA1 immunofluorescence in adult preBötzinger Complex or ventral cervical spinal cords.

After neonatal LPS (1 mg/kg, i.p., (P4), representative confocal images (40x) from adult preBötC (A and B) and cervical spinal cords (C and D) displayed no qualitative differences in immunoreactivity for GFAP (green, astrocytes) or IBA1 (green, microglia) in males (left panels) or females (right panels). PreBötC neurons are labeled with antibodies for NK1R (red, A and B) and motor neurons are labeled with antibodies for ChAT (red, C and D). Neonatal inflammation did not significantly change mean fluorescent intensity of either GFAP or IBA1 in the preBötC (E) or cervical spinal cord (F), suggesting no lasting differences in astrocytes or microglia after neonatal inflammation. Scale bars: 50 µm.

https://doi.org/10.7554/eLife.45399.017

Tables

Table 1
Acute, adult hypoxic phrenic responses.
https://doi.org/10.7554/eLife.45399.019
MaleFemale †††
Neonatal salineNeonatal LPSNeonatal salineNeonatal LPS
Moderate hypoxia114 ± 4193 ± 36185 ± 53*148 ± 63
Keto + Moderate hypoxia118 ± 36118 ± 44165 ± 52189 ± 82*
MaleFemale †
Neonatal SalineNeonatal LPSNeonatal SalineNeonatal LPS
Severe hypoxia139 ± 37106 ± 10172 ± 125172 ± 26
Keto + Severe hypoxia151 ± 25174 ± 96194 ± 45235 ± 63
  1. Group data for adult, acute hypoxic phrenic responses to moderate (PaO235–45 mmHg) and severe (PaO225–35 mmHg) hypoxia demonstrate no differences after neonatal (P4) saline or LPS (1 mg/kg, i.p), or after adult ketoprofen (12.5 mg/kg, i.p, 3 hr) within each sex. Significant differences between sexes demonstrate larger responses in females after moderate or severe hypoxia († p<0.05, ††† p<0.001). *p<0.05 from male neonatal LPS. Moderate hypoxia: neonatal saline male (n = 7), neonatal LPS male (n = 10), neonatal saline female (n = 6), neonatal LPS female (n = 6). Keto + Moderate hypoxia: neonatal saline male (n = 4), neonatal LPS male (n = 4), neonatal saline female (n = 5), neonatal LPS female (n = 5). Severe hypoxia: neonatal saline male (n = 5), neonatal LPS male (n = 4), neonatal saline female (n = 4), neonatal LPS female (n = 4). Keto + Moderate hypoxia: neonatal saline male (n = 5), neonatal LPS male (n = 5), neonatal saline female (n = 5), neonatal LPS female (n = 6)

Table 2
Physiological parameters during electrophysiology experiments.
https://doi.org/10.7554/eLife.45399.021
Temperature (°C)PaO2 (mmHg)PaCO2 (mmHg)pHMAP (mmHg)
BaselineMaleFemaleMaleFemaleMaleFemaleMaleFemaleMaleFemale
Neonatal Saline + mAIH37.4 ± 0.237.4 ± 0.2254 ± 19259 ± 5343.2 ± 5.648.9 ± 3.77.37 ± 0.067.36 ± 0.02124 ± 9121 ± 18
Neonatal LPS + mAIH37.6 ± 0.237.5 ± 0.2266 ± 30268 ± 2442.8 ± 4.7#45.0 ± 1.87.37 ± 0.047.37 ± 0.02127 ± 10123 ± 23
Neonatal Saline + Keto + mAIH37.3 ± 0.137.4 ± 0.3249 ± 21255 ± 2841.7 ± 4.948.6 ± 3.57.38 ± 0.037.33 ± 0.02132 ± 8121 ± 12
NeonatalLPS + Keto + mAIH37.4 ± 0.237.4 ± 0.3276 ± 40283 ± 3341.5 ± 3.247.9 ± 3.67.39 ± 0.037.34 ± 0.02129 ± 16117 ± 14
Neonatal Saline + sAIH37.6 ± 0.337.5 ± 0.2295 ± 18266 ± 943.3 ± 5.947.7 ± 3.17.37 ± 0.027.36 ± 0.00133 ± 6121 ± 19
Neonatal LPS + sAIH37.4 ± 0.137.4 ± 0.4297 ± 28264 ± 3545.3 ± 4.247.7 ± 4.07.36 ± 0.027.36 ± 0.02135 ± 20132 ± 14
Neonatal Saline + Keto + sAIH37.4 ± 0.337.5 ± 0.1256 ± 46268 ± 2941.6 ± 2.2e49.9 ± 3.57.39 ± 0.037.34 ± 0.02110 ± 12113 ± 29
NeonatalLPS + Keto + sAIH37.5 ± 0.237.4 ± 0.2243 ± 45245 ± 3942.3 ± 3.451.6 ± 6.87.37 ± 0.017.31 ± 0.04121 ± 3129 ± 13
NeonatalSaline + CGS-2168037.5 ± 0.237.3 ± 0.2268 ± 21237 ± 1445.4 ± 5.346.2 ± 37.36 ± 0.047.34 ± 0.03119 ± 24121 ± 10
Neonatal LPS + CGS-2168037.6 ± 0.337.4 ± 0.3247 ± 27247 ± 2146.2 ± 2.946.6 ± 2.77.37 ± 0.027.34 ± 0.02114 ± 12107 ± 15
Time Controls37.7 ± 0.1250 ± 4549.4 ± 4.07.36 ± 0.05110 ± 10
Time Controls + Keto37.5 ± 0.3250 ± 1744.0 ± 9.17.37 ± 0.06115 ± 39
CGS-21680 Vehicle Controls37.4 ± 0.3237 ± 4045.8 ± 0.87.37 ± 0.03110 ± 17
Hypoxia
Neonatal Saline + mAIH37.4 ± 0.237.3 ± 0.138 ± 2*,†, ‡40 ± 3*,†, ‡42.2 ± 5.1#48.8 ± 3.87.35 ± 0.077.36 ± 0.03#62 ± 23*,†, ‡65 ± 30*,†, ‡
Neonatal LPS + mAIH37.5 ± 0.437.4 ± 0.139 ± 2*,†, ‡39 ± 4*,†, ‡43.0 ± 4.8#45.4 ± 2.87.36 ± 0.04#7.36 ± 0.02#68 ± 19*,†, ‡80 ± 21
Neonatal Saline + Keto + mAIH37.5 ± 0.237.4 ± 0.338 ± 1*,†, ‡39 ± 3*,†, ‡41.9 ± 3.548.6 ± 3.77.37 ± 0.03#7.32 ± 0.0462 ± 1156 ± 6*,†, ‡
NeonatalLPS + Keto + mAIH37.5 ± 0.237.5 ± 0.340 ± 2*,†, ‡39 ± 4*,†, ‡40.9 ± 2.2#47.8 ± 4.97.36 ± 0.047.32 ± 0.0371 ± 1466 ± 19
Neonatal Saline + sAIH37.6 ± 0.237.4 ± 0.329 ± 5*,†, ‡29 ± 2*,†, ‡43.5 ± 5.947.7 ± 2.37.35 ± 0.037.32 ± 0.0658 ± 9*,†, ‡53 ± 11*,†, ‡
Neonatal LPS + sAIH37.4 ± 0.337.5 ± 0.330 ± 4*,†, ‡31 ± 5*,†, ‡46.3 ± 4.247.3 ± 5.97.34 ± 0.037.31 ± 0.0361 ± 2059 ± 20*,†, ‡
Neonatal Saline + Keto + sAIH37.4 ± 0.237.5 ± 0.230 ± 2*,†, ‡32 ± 3*,†, ‡42.3 ± 2.2#48.9 ± 3.77.36 ± 0.037.29 ± 0.0334 ± 8*,†, ‡,45 ± 29*,†, ‡
NeonatalLPS + Keto + sAIH37.3 ± 0.337.6 ± 0.231 ± 2*,†, ‡32 ± 1*,†, ‡42.2 ± 3.2#52.2 ± 5.87.34 ± 0.037.28 ± 0.0637 ± 11*,†, ‡,43 ± 21*,†, ‡
Time Controls37.6 ± 0.3226 ± 4048.7 ± 4.77.35 ± 0.04107 ± 13
Time Controls + Keto37.5 ± 0.2258 ± 1345.5 ± 9.37.37 ± 0.06#109 ± 44
60 min
Neonatal Saline + mAIH37.5 ± 0.437.3 ± 0.1234 ± 28259 ± 2243.4 ± 5.748.6 ± 3.77.38 ± 0.05#7.35 ± 0.02114 ± 9117 ± 27
Neonatal LPS + mAIH37.5 ± 0.337.4 ± 0.3253 ± 19268 ± 23*42.9 ± 4.4#45.2 ± 2.67.39 ± 0.04#7.37 ± 0.01116 ± 14121 ± 25
Neonatal Saline + Keto + mAIH37.3 ± 0.237.3 ± 0.3262 ± 14257 ± 3242.5 ± 4.948.7 ± 4.07.38 ± 0.017.33 ± 0.04121 ± 13115 ± 11
NeonatalLPS + Keto + mAIH37.6 ± 0.337.6 ± 0.3257 ± 18276 ± 40*41.5 ± 2.747.8 ± 3.67.36 ± 0.027.34 ± 0.06123 ± 11112 ± 18
Neonatal Saline + sAIH37.5 ± 0.337.4 ± 0.2262 ± 36258 ± 1943.7 ± 5.547.6 ± 2.97.37 ± 0.047.32 ± 0.03135 ± 9115 ± 24
Neonatal LPS + sAIH37.7 ± 0.237.4 ± 0.2282 ± 16*266 ± 1846.2 ± 4.847.7 ± 4.57.36 ± 0.027.35 ± 0.02127 ± 14128 ± 17
Neonatal Saline + Keto + sAIH37.7 ± 0.337.4 ± 0.3248 ± 42262 ± 942.3 ± 2.650.2 ± 4.27.37 ± 0.037.32 ± 0.03§105 ± 10109 ± 36
NeonatalLPS + Keto + sAIH37.5 ± 0.237.4 ± 0.3252 ± 24245 ± 2142.2 ± 351.2 ± 6.97.38 ± 0.027.31 ± 0.04117 ± 14125 ± 19
NeonatalSaline + CGS-2168037.3 ± 0.337.6 ± 0.1270 ± 46215 ± 4845.7 ± 4.947 ± 3.37.34 ± 0.067.35 ± 0.04112 ± 30126 ± 21
Neonatal LPS + CGS-2168037.4 ± 0.437.4 ± 0.4254 ± 26256 ± 2146.1 ± 3.246.5 ± 3.27.37 ± 0.017.33 ± 0.04107 ± 16101 ± 25
Time Controls37.5 ± 0.3220 ± 2548.4 ± 3.77.36 ± 0.04102 ± 22
Time Controls + Keto37.6 ± 0.2272 ± 2144.3 ± 8.77.37 ± 0.07111 ± 48
CGS-21680 Vehicle Controls37.6 ± 0.2271 ± 2745.4 ± 1.67.36 ± 0.03108 ± 7
  1. MAP, mean arterial pressure; PaO2, arterial oxygen pressure; PaCO2, arterial carbon dioxide pressure. Neonatal Saline +mAIH male (n = 7) female (n = 7); Neonatal LPS +mAIH male (n = 12) female (n = 6); Neonatal Saline +Keto + mAIH male (n = 4) female (n = 5); Neonatal LPS +Keto + mAIH male (n = 4) female (n = 5); Neonatal Saline +sAIH male (n = 5) female (n = 4); Neonatal LPS +sAIH male (n = 4) female (n = 4); Neonatal Saline +Keto + sAIH male (n = 5) female (n = 5); Neonatal LPS +Keto + sAIH male (n = 5) female (n = 6); Time Control (n = 5); Time Control + Keto (n = 4). Statistical comparisons: ANOVA-RM, Tukey’s post hoc: * different from Time control within time point, different from TC +Keto within time point,  different from baseline and 60 min, § different from baseline, # different from female neonatal LPS +Keto + sAIH within time point, different from female LPS within time point

Table 2—source data 1

Physiological parameters.

https://doi.org/10.7554/eLife.45399.022
Key resources table
Reagent type
(species) or
resource
DesignationSource or
reference
IdentifiersAdditional
information
Chemical compound, drugLPS (Lipopolysaccharides from e Coli (0111:B4))Sigma AldrichL4130dissolved in saline, 1 mg/ml
Chemical compound, drugKeto ((S) - (+) - Ketoprofen)Sigma Aldrich471909dissolved in 50% ethanol in saline,12.5 mg/ml
Chemical compound, drugCGS-21680Sigma AldrichC141dissolved in DMSO to50 mM for storage in aliquots. Dissolved to 100 uM in 10% DMSO and artificial CSF for injections.
Antibodyanti-GFAP (Rabbit polyclonal)Millipore(Millipore Cat# AB5804, RRID:AB_2109645)(1:1000)
Antibodyanti-NK1R (Guinea
pig polyclonal)
Millipore(Millipore Cat#
AB15810, RRID:AB_11213393)
(1:500)
Antibodyanti-IBA1 (Rabbit polyclonal)Wako(Wako Cat# 019–19741, RRID:AB_839504)(1:1000)
Antibodyanti-CHaT (Goat polyclonal)Millipore(Millipore Cat# AB144P, RRID:AB_2079751)(1:300)
Antibodydonkey-anti-rabbit 647 IgG secondaryLife Technologies(Molecular Probes Cat# A-31573, RRID:AB_2536183)(1:1000)
Antibodydonkey-anti-goat 555 IgG secondaryLife Technologies(Molecular Probes Cat# A-21432, RRID:AB_141788)(1:1000)
Antibodydonkey-anti-guinea pig 488 IgG secondaryJackson Immuno(Jackson ImmunoResearch Labs Cat# 706-545-148, RRID:AB_2340472)(1:1000)
Sequence-based reagentIL-1β forward primerIntegrated DNA TechnologiesCTG CAG ATG CAA TGG AAA GA
Sequence-based reagentIL-1β reverse primerIntegrated DNA TechnologiesTTG CTT CCA AGG CAG ACT TT
Sequence-based reagentIL-6 forward primerIntegrated DNA TechnologiesGTG GCT AAG GAC CAA GAC CA
Sequence-based reagentIL-6 reverse primerIntegrated DNA TechnologiesGGT TTG CCG AGT AGA CCT CA
Sequence-based reagentiNOS forward primerIntegrated DNA TechnologiesAGG GAG TGT TGT TCC AGG TG
Sequence-based reagentiNOS reverse primerIntegrated DNA TechnologiesTCT GCA GGA TGT CTT GAA CG
Sequence-based reagentTNFα forward primerIntegrated DNA TechnologiesTCC ATG GCC CAG ACC CTC ACA C
Sequence-based reagentTNFα reverse primerIntegrated DNA TechnologiesTCC GCT TGG TGG TTT GCT ACG
Sequence-based reagentCOX2 forward primerIntegrated DNA TechnologiesTGT TCC AAC CCA TGT CAA AA
Sequence-based reagentCOX2 reverse primerIntegrated DNA TechnologiesCGT AGA ATC CAG TCC GGG TA
Sequence-based reagent18 s forward primerIntegrated DNA TechnologiesCGG GTG CTC TTA GCT GAG TGT CCC
Sequence-based reagent18 s reverse primerIntegrated DNA TechnologiesCTC GGG CCT GCT TTG AAC AC

Data availability

All data generated or analyzed during this study are included in the manuscript and supporting files. Source data are available for all figures.

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