Mitochondrial function in peripheral blood mononuclear cells of dairy cows subjected to an LPS-induced inflammatory challenge

Abstract

Mitochondria play a central role in energy metabolism and cellular stress responses, and circulating PBMCs can serve as biomarkers of mitochondrial function. The objective of this study was to assess mitochondrial function in PBMCs from dairy cows subjected to an acute LPS-induced inflammatory challenge using pair-fed control cows. Sixteen multiparous Holstein cows (639 ± 68 kgBW, 3.0 ± 1.4 BCS) were infused intravenously with LPS (Escherichia coli O55:B5; 62.5 ng/kgBW; LPS, n = 8) or sterile saline (CTRL, n = 8) at 15 ± 8 days postpartum. Cows were fed a TMR (18% CP and 36% NDF at DM) at 100% of nutrient requirements and milked twice daily. Infusion with LPS induced a 36% decrease in dry matter intake which resulted in a 13% decrease in milk yield. By design, CTRL cows were pair-fed to match the intake of LPS cows, resulting in no differences between treatments in dry matter intake or milk yield. The inflammatory response was confirmed by increased rectal temperature (maximum mean 40.3°C at 3 h post-infusion), heart rate (103 beats/min), and respiratory rate (70 breaths/min). Blood was collected six hours after infusion and PBMCs were isolated using the Ficoll–Paque gradient method. Mitochondrial oxygen consumption rates were measured oligomycin, carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone (FCCP), and antimycin A plus rotenone with an Oxytherm Hansatech. Data were analyzed using the MIXED procedure of SAS, including treatment as a fixed effect. Basal and oligomycin-resistant respiration were increased in LPS compared with CTRL cows (11.3 vs. 4.3 ± 1.7 and 4.3 vs. 2.1 ± 0.6 nmolO₂/min/10⁶ cells, P < 0.05), resulting in greater ATP-linked respiration (7.0 vs. 2.2 ± 1.4 nmolO₂/min/10⁶ cells, P < 0.05). The mitochondrial uncoupler FCCP did not further increase oxygen consumption rates. In conclusion, acute LPS-induced inflammation increases mitochondrial ATP demand in PBMCs of dairy cows, supporting their use as indicators of systemic mitochondrial energy requirements during inflammation.