Breed-specific differences in the immune response to lipopolysaccharide in ewes.

Innate immune response to a lipopolysaccharide (LPS) challenge varies among sheep breeds. How different breeds respond to bacterial infections impacts management practices of sheep producers. Hence, clinical response, acute-phase response, and gene expression of pro- and anti-inflammatory markers in peripheral white blood cells (WBCs) were examined after an LPS challenge in Dorset and Suffolk ewes. Ewes received either PBS or 2.5 µg/kg LPS (i.v.) 4 to 5 d after onset of synchronized estrus. Blood was collected via jugular venipuncture intermittently for 24 h to determine WBC counts. Rectal temperatures and observations of behavioral/physical appearances were recorded hourly. After LPS, WBCs decreased the first hour (P = 0.0001) and rectal temperatures (P < 0.0001) increased through 4 h; both returned toward normal 6 h after challenge. Suffolk ewes exhibited greater changes in temperature (P = 0.03) and behavioral/physical responses (P < 0.0001) than Dorset ewes and had an enhanced acute-phase response demonstrated by increased concentrations of plasma haptoglobin (P = 0.04), as well as cortisol concentrations (P = 0.03). Real-time PCR was completed on buffy coat homogenates for expression of pro-inflammatory [CXCL8, IL-6, interferon gamma (IFNG), complement component 3 (C3), toll-like receptor 4 (TLR4), prostaglandin synthase 2 (PTGS2)] and anti-inflammatory [IL-10, superoxide dismutase 2 (SOD2), forkhead box P3 (FOXP3), peroxisome proliferator-activated receptor gamma (PPARG), mannose receptor C type 1 (MRC1), transforming growth factor ß (TGFß)] genes. After LPS treatment, gene expressions increased for CXCL8 (P = 0.0003), TLR4 (P = 0.004), SOD2 (P < 0.0001), and C3 (P = 0.003), while PPARG (P = 0.006) and MRC1 (P = 0.003) decreased. Overall, Dorset ewes had greater expression of TLR4 (P = 0.003), IL-10 (P = 0.045), PPARG (P = 0.002), FOXP3 (P = 0.001), and SOD2 (P = 0.0002), whereas Suffolk ewes had greater expression of IL-6 (P = 0.0007), IFNG (P = 0.02), PTGS2 (P = 0.0002), and C3 (P = 0.008). Suffolk ewes also displayed greater expression of IL-6 (P = 0.002) and C3 (P = 0.0004) in response to LPS. In conclusion, differences in gene expression may explain the enhanced inflammatory response in Suffolk ewes and may predispose Suffolk ewes to be more responsive to bacterial infection than Dorset ewes.

N-acetylcysteine reverses cardiac myocyte dysfunction in a rodent model of behavioral stress.

Compelling clinical reports reveal that behavioral stress alone is sufficient to cause reversible myocardial dysfunction in selected individuals. We developed a rodent stress cardiomyopathy model by a combination of prenatal and postnatal behavioral stresses (Stress). We previously reported a decrease in percent fractional shortening by echo, both systolic and diastolic dysfunction by catheter-based hemodynamics, as well as attenuated hemodynamic and inotropic responses to the ß-adrenergic agonist, isoproterenol (ISO) in Stress rats compared with matched controls (Kan H, Birkle D, Jain AC, Failinger C, Xie S, Finkel MS. J Appl Physiol 98: 77-82, 2005). We now report enhanced catecholamine responses to behavioral stress, as evidenced by increased circulating plasma levels of norepinephrine (P < 0.01) and epinephrine (P < 0.01) in Stress rats vs. controls. Cardiac myocytes isolated from Stress rats also reveal evidence of oxidative stress, as indicated by decreased ATP, increased GSSG, and decreased GSH-to-GSSG ratio in the presence of increased GSH peroxidase and catalase activities (P < 0.01, for each). We also report blunted inotropic and intracellular Ca(2+) concentration responses to extracellular Ca(2+) (P < 0.05), as well as altered inotropic responses to the intracellular calcium regulator, caffeine (20 mM; P < 0.01). Treatment of cardiac myocytes with N-acetylcysteine (NAC) (10(-3) M) normalized calcium handling in response to ISO and extracellular Ca(2+) concentration and inotropic response to caffeine (P < 0.01, for each). NAC also attenuated the blunted inotropic response to ISO and Ca(2+) (P < 0.01, for each). Surprisingly, NAC did not reverse the changes in GSH, GSSG, or GSH-to-GSSG ratio. These data support a GSH-independent salutary effect of NAC on intracellular calcium signaling in this rodent model of stress-induced cardiomyopathy.