Hematologic, prostaglandin F2α -metabolite, serum amyloid A, and serum iron changes in horses with experimentally induced endotoxemia

An updated description of bacterial pneumonia in adult horses and factors associated with death

BACKGROUND

Available descriptive studies on equine pneumonia are outdated or focus on specific horse or bacterial populations.

OBJECTIVES

To describe the clinical presentation and bacterial isolates of adult horses with bacterial pneumonia and identify factors associated with death.

ANIMALS

One hundred sixteen horses >2 years old with bacterial pneumonia.

METHODS

Retrospective case series. Data regarding history, physical examination, clinicopathologic features, treatment, bacterial culture and sensitivity, and outcome were collected and analyzed retrospectively.

RESULTS

Historical risk factors were present for 60% of cases, whereas abnormal vital signs on intake were present for <50%. Most horses (58%) underwent at least 1 change of antimicrobial treatment, and 67% received the highest-priority critically important antimicrobials. Streptococcus zooepidemicus was the most isolated bacteria (44%), followed by Escherichia coli (19%), Klebsiella spp. (18%), other Streptococcus species (17%), and Bacillus spp. (13%). Fusobacterium spp. were the most common anaerobic isolates (11%). Antimicrobial susceptibility varied widely. Survival to discharge was 73%. Heart rate at presentation (odds ratio [OR] 1.08, 95% confidence interval [CI] 1.008-1.17, P = .03) and higher creatinine (OR 14.1, 95% CI 1.56-127.6, P = .02) increased the risk of death. Higher lymphocyte count (OR 0.27, 95% CI 0.08-0.94, P = .04) reduced risk.

CONCLUSIONS AND CLINICAL IMPORTANCE

Contrasting older literature, Fusobacterium spp. were the most common anaerobes. Streptococcus zooepidemicus remained the most common isolate and was predictably susceptible to penicillin. Antimicrobial susceptibility was otherwise variable and broad applicability is limited as this was a single-center study. Increased risk of death associated with tachycardia and abnormally high serum creatinine concentration is consistent with previous studies.

Cardiac-specific overexpression of catalase attenuates lipopolysaccharide-induced cardiac anomalies through reconciliation of autophagy and ferroptosis

Lipopolysaccharide (LPS) from Gram-negative bacteria is a major contributor to cardiovascular failure, but the signaling mechanisms underlying its stress response are not fully understood. This study aimed to investigate the effect of the antioxidant enzyme catalase on LPS-induced cardiac abnormalities and the mechanisms involved, with particular focus on the interplay between autophagy, ferroptosis, and apoptosis. Cardiac-specific catalase (CAT) overexpression and wild-type (WT) mice were stimulated with LPS (6 mg/kg, intravenous injection), and cardiac morphology and function were evaluated. Oxidative stress, ferroptosis, apoptosis, and mitochondrial status were monitored, and survival curves were plotted based on the results of LPS stimulation. The results showed that, compared with WT mice, mice overexpressing catalase had a higher survival rate under LPS stimulation. Ultrasound echocardiography, cardiomyocyte characteristics, and Masson's trichrome staining showed that LPS inhibited cardiac function and caused cardiac fibrosis, while catalase alleviated these adverse effects. LPS increased apoptosis (TUNEL, caspase-3 activation, cleaved caspase-3), increased O₂^·- production, induced inflammation (TNF-α), autophagy, iron toxicity, and carbonyl damage, and significantly damaged mitochondria (mitochondrial membrane potential, mitochondrial proteins, and ultrastructure). These effects were significantly alleviated by catalase. Interestingly, the antioxidant N-acetylcysteine, autophagy inhibitor 3-methyladenine, and ferroptosis inhibitor lipostatin-1 all eliminated the LPS-induced contraction dysfunction and ferroptosis (using lipid peroxidation). Induction of ferroptosis could eliminate the cardioprotective effect of NAC. In conclusion, catalase rescues LPS-induced cardiac dysfunction by regulating oxidative stress, autophagy, ferroptosis, apoptosis, and mitochondrial damage in cardiomyocytes.

The Clinical Pharmacology and Therapeutic Evaluation of Non-Steroidal Anti-Inflammatory Drugs in Adult Horses

This review firstly examines the underlying pathophysiology of pain and inflammation associated with orthopedic disease and endotoxemia. Then, it reviews the clinical pharmacology (pharmacokinetics and pharmacodynamics) of both conventional and non-conventional NSAIDs in the adult horse, and finally provides an overview of different modalities to evaluate the therapeutic efficacy of NSAIDs in research.

Pharmacokinetics and efficacy of orally administered acetaminophen (paracetamol) in adult horses with experimentally induced endotoxemia

BACKGROUND

Acetaminophen has been evaluated in horses for treatment of musculoskeletal pain but not as an antipyretic.

OBJECTIVES

To determine the pharmacokinetics and efficacy of acetaminophen compared to placebo and flunixin meglumine in adult horses with experimentally induced endotoxemia.

ANIMALS

Eight university owned research horses with experimentally induced endotoxemia.

METHODS

Randomized placebo controlled crossover study. Horses were treated with acetaminophen (30 mg/kg PO; APAP), flunixin meglumine (1.1 mg/kg, PO; FLU), and placebo (PO; PLAC) 2 hours after administration of LPS. Plasma APAP was analyzed via LC-MS/MS. Serial CBC, lactate, serum amyloid A, heart rate and rectal temperature were evaluated. Serum IL-1β, IL-6, IL-8, IL-10, and TNF-α were evaluated by an equine-specific multiplex assay.

RESULTS

Mean maximum plasma APAP concentration was 13.97 ± 2.74 μg/mL within 0.6 ± 0.3 hour after administration. At 4 and 6 hours after treatment, both APAP (P = <.001, P = .03, respectively) and FLU (P = .0045 and P < .001, respectively) had a significantly greater decrease in rectal temperature compared to placebo. FLU caused greater heart rate reduction than APAP at 4 and 6 hours (P = .004 and P = .04), and PLAC at 4 hours (P = .05) after treatment.

CONCLUSIONS AND CLINICAL IMPORTANCE

The pharmacokinetics of acetaminophen in endotoxemic horses differ from those reported by previous studies in healthy horses. Acetaminophen is an option for antipyresis in clinical cases, particularly when administration of traditional NSAIDs is contraindicated.

Hemodynamic changes in cytokines, chemokines, acute phase proteins and prostaglandins in mares with subclinical endometritis

Apparently healthy mares with conception failure or embryonic loss may have subclinical endometritis (SE). Our objective was to document evidence of systemic immune responses against SE in mares. In apparently healthy (control) mares as well as those with chronic endometritis (ChE) or subacute suppurative endometritis (SSE), both considered classes of SE, serum concentrations of cytokines (IL-1β, IL-6, IL-10 and TNF_-α), chemokines (IL-8), acute phase protein (SAA), and plasma concentrations of prostaglandins (PGF_2α and PGE₂) were measured using validated enzyme linked immunoassays (EIA). Mixed-breed mares of known reproductive history, were used. Based on an endometrial cytological examination, mares were allocated into the following groups: healthy (control), ChE, and SSE (12, 26 and 11 mares, respectively). Serum concentrations of IL-6, IL-8 and IL-10 and plasma PGF_2α concentrations were increased (P < 0.01) in mares with SSE compared to healthy mares. Furthermore, serum concentrations of IL-6 (P < 0.05) and IL-10 (P < 0.05) were elevated in the ChE group compared to the healthy group whereas serum SAA (P < 0.01) and plasma PGE₂ (P < 0.05) were higher in healthy mares compared to ChE and SSE mares. However, serum concentrations of IL-1β and TNF_-α were not significantly different among groups. In conclusion, there were two novel findings: (1) development of serum testing for a set of biochemical markers has promise to explore the pathogenesis of inflammation in mares with SE; and (2) none of the individual biomarkers studied, excluding IL-8, was a significant predictor of SE. However, serum IL-6:IL-10 and IL-6:TNF_-α concentrations, as well as plasma PGE₂:PGF_2α ratios, may yield a novel diagnostic marker for chronic subclinical endometritis.