A Preclinical Model of Sepsis-Induced Myopathy with Disuse in Mice

Sepsis is a major cause of in-hospital deaths. Improvements in treatment result in a greater number of sepsis survivors. Approximately 75% of the ...

University of Florida

Cardiorespiratory dysfunction resulting from doxorubicin (DOX) chemotherapy treatment is a debilitating condition affecting cancer patient outcomes and quality of life. DOX treatment promotes cardiac and respiratory muscle pathology due to enhanced reactive oxygen species (ROS) production, mitochondrial dysfunction and impaired muscle contractility. In contrast, hyperbaric oxygen (HBO) therapy is considered a controlled oxidative stress that can evoke a substantial and sustained increase in muscle antioxidant expression. This HBO-induced increase in antioxidant capacity has the potential to improve cardiac and respiratory (i.e., diaphragm) muscle redox balance, preserving mitochondrial function and preventing muscle dysfunction. Therefore, we determined whether HBO therapy prior to DOX treatment is sufficient to enhance muscle antioxidant expression and preserve muscle redox balance and cardiorespiratory muscle function. To test this, adult female Sprague Dawley rats received HBO therapy (2 or 3 atmospheres absolute (ATA), 100% O, 1 h/day) for 5 consecutive days prior to acute DOX treatment (20 mg/kg i.p.). Our data demonstrate that 3 ATA HBO elicits a greater antioxidant response compared to 2 ATA HBO. However, these effects did not correspond with beneficial adaptations to cardiac systolic and diastolic function or diaphragm muscle force production in DOX treated rats. These findings suggest that modulating muscle antioxidant expression with HBO therapy is not sufficient to prevent DOX-induced cardiorespiratory dysfunction.

Effects of Hyperbaric Oxygen Preconditioning on Doxorubicin Cardiorespiratory Toxicity.

This study aimed to evaluate the acute effects of aerobic and resistance exercises on blood pressure and endothelial blood markers. We also correlated post-exercise blood pressure response with baseline cardiovascular parameters in middle-aged patients with hypertension. This cross-sectional study randomized 54 volunteers into the aerobic exercise group (AG,  = 27; 45.6 ± 7.7 years) or dynamic resistance exercise group (RG,  = 27; 45.8 ± 8.4 years). Blood marker evaluation, cardiopulmonary exercise tests, resting blood pressure monitoring, ambulatory blood pressure monitoring (ABPM), flow-mediated dilatation monitoring, and body composition evaluation were carried out. Exercise sessions were performed to evaluate post-exercise hypotension (PEH) and endothelial marker responses, in addition to post-exercise ABPM (ABPMex). This study is an arm of the study which was approved by the local ethics committee (No. 69373217.3.0000.5347) in accordance with the Helsinki Declaration and was registered at ClinicalTrials.gov (NCT03282942). The AG performed walking/running at 60% of the reserve heart rate, while the RG performed 10 exercises with two sets of 15-20 repetitions. The mean 24 h ABPM and ABPMex values showed no significant statistical differences. Systolic and diastolic blood pressure hypotension after aerobic and dynamic resistance were -10.59 ± 5.24/-6.15 ± 6.41 mmHg and -5.56 ± 7.61/-6.20 ± 8.25 mmHg, respectively. For an up-to-7 h assessment of resting pressure, there was a positive effect in the aerobic group. The concentrations of nitrites/nitrates (NOx) and endothelin-1 (ET-1) did not change during hypotension. Moreover, PEH and ABPMex were significantly correlated with baseline health variables. Thus, when middle-aged patients with hypertension perform aerobic or resistance exercise, the NOx/ET-1 pathway does not provide the best explanation for PEH. Finally, we found associations between baseline cardiovascular variables and endothelial vasoconstrictors with PEH.

Effects of exercise modalities on decreased blood pressure in patients with hypertension.

Different types of muscle contraction can cause different damage to the musculature and differences in inflammatory responses. Acute increases in circulatory inflammation markers can influence the crosstalk between coagulation and fibrinolysis processes, increasing the risk of thrombus formation and detrimental cardiovascular events. The aim of this study was to analyze the effects of concentric and eccentric exercise on hemostasis markers, C-reactive protein (CRP), and the relationship between these variables. Eleven healthy subjects with a mean age of 25.4 ± 2.8, non-smokers, with no history of cardiovascular disease and blood type O, randomly performed an isokinetic exercise protocol consisting of 75 concentric (CP) or eccentric (EP) contractions of knee extension, divided into five sets of 15 repetitions combined with 30-s rest. Blood samples for analysis of FVIII, von Willebrand factor, tissue plasminogen activator (t-PA), plasminogen activator inhibitor type-1 (PAI-1), and CRP were collected pre, post, 24 h, and 48 h after each protocol. Increased levels of CRP at 48 h in EP versus CP ( = 0.002), increased PAI-1 activity 48 h in EP versus CP ( = 0.044), and a reduction in t-PA at 48 h when compared with post-protocol in both protocols ( = 0.001). A correlation was found between CRP and PAI-1 at 48 h of PE ( = 0.69;  = 0.02). This study showed that both EP and CP increase the clotting process, albeit only the exercise performed eccentrically induces inhibition of fibrinolysis. This is possibly due to the increase in PAI-1 48 h after the protocol, which correlates with the increase in inflammation as demonstrated by the CRP levels.

Eccentric, but not concentric muscle contraction induce inflammation and impairs fibrinolysis in healthy young men.

Doxorubicin (DOX) is a chemotherapeutic agent highly effective at limiting cancer progression. Despite the efficacy of this anticancer drug, the clinical use of DOX is limited due to cardiotoxicity. The cardiac mitochondria are implicated as the primary target of DOX, resulting in inactivation of electron transport system complexes, oxidative stress, and iron overload. However, it is established that the cardiac mitochondrial subpopulations reveal differential responses to DOX exposure, with subsarcolemmal (SS) mitochondria demonstrating redox imbalance and the intermyofibrillar (IMF) mitochondria showing reduced respiration. In this regard, exercise training is an effective intervention to prevent DOX-induced cardiac dysfunction. Although it is clear that exercise confers mitochondrial protection, it is currently unknown if exercise training mitigates DOX cardiac mitochondrial toxicity by promoting beneficial adaptations to both the SS and IMF mitochondria. To test this, SS and IMF mitochondria were isolated from sedentary and exercise-preconditioned female Sprague Dawley rats exposed to acute DOX treatment. Our findings reveal a greater effect of exercise preconditioning on redox balance and iron handling in the SS mitochondria of DOX-treated rats compared to IMF, with rescue of cardiolipin synthase 1 expression in both subpopulations. These results demonstrate that exercise preconditioning improves mitochondrial homeostasis when combined with DOX treatment, and that the SS mitochondria display greater protection compared to the IMF mitochondria. These data provide important insights into the molecular mechanisms that are in part responsible for exercise-induced protection against DOX toxicity.

Exercise and Doxorubicin Modify Markers of Iron Overload and Cardiolipin Deficiency in Cardiac Mitochondria.

Doxorubicin (DOX) is a highly effective chemotherapy agent prescribed for cancer treatment. However, the clinical use of DOX is limited due to off-target toxicity in healthy tissues. In this regard, hepatic and renal metabolic clearance results in DOX accumulation within these organ systems. Within the liver and kidneys, DOX causes inflammation and oxidative stress, which promotes cytotoxic cellular signaling. While there is currently no standard of care to treat DOX hepatic- and nephrotoxicity, endurance exercise preconditioning may be an effective intervention to prevent elevations in liver alanine transaminase (ALT) and aspartate aminotransferase (AST) and to improve kidney creatinine clearance. To determine whether exercise preconditioning is sufficient to reduce liver and kidney toxicity resulting from acute exposure to DOX chemotherapy treatment, male and female Sprague-Dawley rats remained sedentary or were exercise trained prior to saline or DOX exposure. Our findings demonstrate that DOX treatment elevated AST and AST/ALT in male rats, with no effects of exercise preconditioning to prevent these increases. We also showed increased plasma markers of renin-angiotensin-aldosterone system (RAAS) activation and urine markers of proteinuria and proximal tubule damage, with male rats revealing greater differences compared to females. Exercise preconditioning showed improved urine creatinine clearance and reduced cystatin c in males, while females had reduced plasma angiotensin II (AngII) levels. Our results demonstrate both tissue- and sex-specific responses related to the effects of exercise preconditioning and DOX treatment on markers of liver and kidney toxicity.

Effects of Exercise Preconditioning on Doxorubicin-Induced Liver and Kidney Toxicity in Male and Female Rats.

Acute hyperbaric O (HBO) therapy after spinal cord injury (SCI) can reduce inflammation and increase neuronal survival. To our knowledge, it is unknown if these benefits of HBO require hyperbaric vs. normobaric hyperoxia. We used a C4 lateralized contusion SCI in adult male and female rats to test the hypothesis that the combination of hyperbaria and 100% O (i.e. HBO) more effectively mitigates spinal inflammation and neuronal loss, and enhances respiratory recovery, as compared to normobaric 100% O. Experimental groups included spinal intact, SCI no O therapy, and SCI + 100% O delivered at normobaric pressure (1 atmosphere, ATA), or at 2- or 3 ATA. O treatments lasted 1-h, commenced within 2-h of SCI, and were repeated for 10 days. The spinal inflammatory response was assessed with transcriptomics (RNAseq) and immunohistochemistry. Gene co-expression network analysis showed that the strong inflammatory response to SCI was dramatically diminished by both hyper- and normobaric O therapy. Similarly, both HBO and normobaric O treatments reduced the prevalence of immunohistological markers for astrocytes (glial fibrillary acidic protein) and microglia (ionized calcium binding adaptor molecule) in the injured spinal cord. However, HBO treatment also had unique impacts not detected in the normobaric group including upregulation of an anti-inflammatory cytokine (interleukin-4) in the plasma, and larger inspiratory tidal volumes at 10-days (whole body-plethysmography measurements). We conclude that normobaric O treatment can reduce the spinal inflammatory response after SCI, but pressured O (i.e., HBO) provides further benefit.

Franccesco P. Boeno

Department of Applied Physiology and Kinesiology,
College of Health and Human Performance,
Department of Applied Physiology and Kinesiology, College of Health and Human Performance

University of Florida

A Preclinical Model of Sepsis-Induced Myopathy with Disuse in Mice

Franccesco P. Boeno

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Applied Physiology and Kinesiology,College of Health and Human Performance,Department of Applied Physiology and Kinesiology, College of Health and Human Performance

University of Florida

A Preclinical Model of Sepsis-Induced Myopathy with Disuse in Mice

Department of Applied Physiology and Kinesiology,
College of Health and Human Performance,
Department of Applied Physiology and Kinesiology, College of Health and Human Performance