Cross-sectional associations of pulmonary function with systemic inflammation and oxidative stress in individuals with chronic spinal cord injury

Diagnosis and Management of Cardiovascular Risk in Individuals With Spinal Cord Injury: A Narrative Review

More than 16 000 Americans experience spinal cord injury (SCI), resulting in chronic disability and other secondary sequelae, each year. Improvements in acute medical management have increased life expectancy. Cardiovascular disease is a leading cause of death in this population, and seems to occur earlier in individuals with SCI compared with the general population. People with SCI experience a high burden of traditional cardiovascular disease risk factors, including dyslipidemia and diabetes, and demonstrate anatomic, metabolic, and physiologic changes alongside stark reductions in physical activity after injury. They also experience multiple, complex barriers to care relating to disability and, in many cases, compounding effects of intersecting racial and socioeconomic health inequities. Given this combination of risk factors, some investigators have proposed that people with SCI are at increased risk for cardiovascular disease, beyond that associated with traditional risk factors, and SCI could be considered a risk-enhancing factor, analogous to other risk-enhancing factors defined by the 2019 American Heart Association/American College of Cardiology Primary Prevention Guidelines. However, more research is needed in this population to clarify the role of traditional risk factors, novel risk factors, health care access, social determinants of health, and intersectionality of disability, race, and socioeconomic status. There is an urgent need for primary care physicians and cardiologists to have awareness of the importance of timely diagnosis and management of cardiac risk factors for people with SCI.

Systemic and Pulmonary Inflammation/Oxidative Damage: Implications of General and Respiratory Muscle Training in Chronic Spinal-Cord-Injured Patients

Chronic spinal cord injury affects several respiratory-function-related parameters, such as a decrease in respiratory volumes associated with weakness and a tendency to fibrosis of the perithoracic muscles, a predominance of vagal over sympathetic action inducing airway obstructions, and a difficulty in mobilizing secretions. Altogether, these changes result in both restrictive and obstructive patterns. Moreover, low pulmonary ventilation and reduced cardiovascular system functionality (low venous return and right stroke volume) will hinder adequate alveolar recruitment and low O₂ diffusion, leading to a drop in peak physical performance. In addition to the functional effects described above, systemic and localized effects on this organ chronically increase oxidative damage and tissue inflammation. This narrative review describes both the deleterious effects of chronic spinal cord injury on the functional effects of the respiratory system as well as the role of oxidative damage/inflammation in this clinical context. In addition, the evidence for the effect of general and respiratory muscular training on the skeletal muscle as a possible preventive and treatment strategy for both functional effects and underlying tissue mechanisms is summarized.

Improved pulmonary function is associated with reduced inflammation after hybrid whole-body exercise training in persons with spinal cord injury

NEW FINDINGS

What is the central question of this study? Does 12 weeks of functional electrical stimulation (FES) rowing exercise training lead to suppressed systemic inflammation and an improvement in pulmonary function in persons with sub-acute spinal cord injury (SCI)? What is the main finding and its importance? Twelve weeks of FES rowing exercise improves pulmonary function and the magnitude of improvement is associated with reductions in inflammatory biomarkers. Thus, interventions targeting inflammation may lead to better pulmonary outcomes for person with sub-acute SCI.

ABSTRACT

The current study was designed to test the hypotheses that (1) reducing systemic inflammation via a 12-week functional electrical stimulation rowing exercise training (FESRT) prescription results in augmented pulmonary function, and (2) the magnitude of improvement in pulmonary function is inversely associated with the magnitude of systemic inflammation suppression in persons with sub-acute (≤2 years) spinal cord injury (SCI). We conducted a retrospective analysis of a randomized controlled trial (NCT#02139436). Twenty-one participants were enrolled (standard of care (SOC; n = 9) or FESRT (n = 12)). The exercise prescription was three sessions/week at 70-85% of peak heart rate. A two-way analysis of covariance and regression analysis was used to assess group differences and associations between pulmonary function, log transformed high-sensitivity C-reactive protein (hsCRPlog ) and white blood cell count (WBC). Following FESRT, clinically significant improvements in forced expiratory volume in 1 s (FEV1 ; 0.25 (0.08-0.43) vs. -0.06 (-0.26 to 0.15) litres) and forced vital capacity (0.22 (0.04-0.39) vs. 0.08 (-0.29 to 0.12) litres) were noted and systemic WBC (-1.45 (-2.48 to -0.50) vs. 0.41 (-0.74 to 1.56) μl) levels were suppressed compared to SOC (mean change (95% confidence interval); P < 0.05). Additionally, both ΔhsCRPlog and ΔWBC were predictors of ΔFEV1 (r2  = 0.89 and 0.43, respectively; P < 0.05). Twelve weeks of FESRT improves pulmonary function and reduces WBC in persons with sub-acute SCI. The potency of FESRT to augment pulmonary function may depend on adequate suppression of systemic inflammation.

Systemic inflammation after spinal cord injury: A review of biological evidence, related health risks, and potential therapies

Individuals with chronic traumatic spinal cord injury (SCI) develop progressive multi-system health problems that result in clinical illness and disability. Systemic inflammation is associated with many of the common medical complications and acquired diseases that accompany chronic SCI, suggesting that it contributes to a number of comorbid pathological conditions. However, many of the mechanisms that promote persistent systemic inflammation and its consequences remain ill-defined. This review describes the significant biological factors that contribute to systemic inflammation, major organ systems affected, health risks, and the potential treatment strategies. We aim to highlight the need for a better understanding of inflammatory processes, and to establish appropriate strategies to address inflammation in SCI.

Aging and Susceptibility to Pulmonary Disease

The lungs are continually subjected to noxious and inert substances, are immunologically active, and are in a constant state of damage and repair. This makes the pulmonary system particularly vulnerable to diseases of aging. Aging can be understood as random molecular damage that is unrepaired and accumulates over time, resulting in cellular defects and tissue dysfunction. The breakdown of cellular mechanisms, including stem cell exhaustion, genomic instability, telomere attrition, epigenetic alteration, loss of proteostasis, deregulated nutrient sensing, mitochondrial dysfunction, cellular senescence, altered intercellular communication, and changes in the extracellular matrix is thought to advance the aging process itself. Chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), and cancers illustrate a pathologic breakdown in these mechanisms beyond normal aging. The immune system becomes less effective with advancing age. There is a low-level state of chronic inflammation termed inflammaging which is thought to be driven by immunosenescence, the changes in the innate and adaptive immune systems with advancing age that lead to dysregulation and decreased effectiveness of the immune system. These processes of aging lead to expected changes in the form and function of the respiratory system, most notably a loss of lung elasticity, decrease in respiratory muscle strength, increase in ventilation-perfusion mismatching, and stiffening of the vasculature. The astute clinician is aware of these expected findings and does not often attribute dyspnea to aging alone. Maintaining a low threshold to investigate for comorbid disease and understanding how pulmonary disease presents differently in the elderly than in younger adults can improve clinical outcomes. © 2022 American Physiological Society. Compr Physiol 12:3509-3522, 2022.

Inflammation and Oxidative Stress as Common Mechanisms of Pulmonary, Autonomic and Musculoskeletal Dysfunction after Spinal Cord Injury

Simple Summary

When a spinal cord injury occurs, the neurons that regulate our voluntary movements, those involved in environment and somatic perception and those that regulate vegetative functions are affected. Once neuronal damage is established, the cells of other tissues are also affected in their functions, altering the interaction between organs and altering the proper functioning of the organism. Multiple studies in animal models, as well as in humans, have recognized as factors involved in organ damage the imbalance between the formation of highly reactive molecules called pro-oxidants and defensive mechanisms called antioxidants. Closely associated with this phenomenon, the inflammatory response is also pathologically activated. In this narrative review, we have analyzed the information involving these pathological processes at the level of the lung, the autonomic nervous system and the skeletal musculature after spinal cord injury. Knowing the abnormal functioning mechanisms that occur after a spinal cord injury not only offers a better understanding of the organic events but also offers future possibilities for therapeutic interventions that may benefit the thousands of patients suffering this pathology.

Abstract

One of the etiopathogenic factors frequently associated with generalized organ damage after spinal cord injury corresponds to the imbalance of the redox state and inflammation, particularly of the respiratory, autonomic and musculoskeletal systems. Our goal in this review was to gain a better understanding of this phenomenon by reviewing both animal and human studies. At the respiratory level, the presence of tissue damage is notable in situations that require increased ventilation due to lower thoracic distensibility and alveolar inflammation caused by higher levels of leptin as a result of increased fatty tissue. Increased airway reactivity, due to loss of sympathetic innervation, and levels of nitric oxide in exhaled air that are similar to those seen in asthmatic patients have also been reported. In addition, the loss of autonomic control efficiency leads to an uncontrolled release of catecholamines and glucocorticoids that induce immunosuppression, as well as a predisposition to autoimmune reactions. Simultaneously, blood pressure regulation is altered with vascular damage and atherogenesis associated with oxidative damage. At the muscular level, chronically elevated levels of prooxidants and lipoperoxidation associated with myofibrillar atrophy are described, with no reduction or reversibility of this process through antioxidant supplementation.

The Repression of the HMGB1-TLR4-NF-κB Signaling Pathway by Safflower Yellow May Improve Spinal Cord Injury

Spinal cord injury (SCI) often results in abnormal sensory and motor functions. Current interventions for SCI in the clinical setting are not effective partly due to the complexity concerning its pathophysiological mechanism. In the wake of SCI, considerable inflammatory cells assemble around the injured area that induces a series of inflammatory reactions and aggravates tissue lesions, thereby affecting the recovery of the damaged nerve tissue. Therefore, the inhibition of inflammatory responses can improve the repair of the injured spinal cord tissue. Safflower Yellow (SY) is the main active ingredient of Carthamus tinctorius. SY has anti-inflammatory effect, as it can inhibit IκBα phosphorylation to impede the NF-κB signaling pathway and p53 nuclear translocation. Besides, SY can limit the release of pro-inflammatory factors, which in turn may alleviate secondary SCI and prevent further complications. In this report, we analyze the pathophysiological mechanism of SCI, the role of inflammatory responses, and how SY interferes with the HMGB1-TLR-4-NF-κB signaling pathway to attenuate inflammatory responses in SCI.

Ibuprofen use is associated with reduced C-reactive protein and interleukin-6 levels in chronic spinal cord injury

Objective: To assess the association between ibuprofen use and the systemic inflammatory biomarkers C-reactive protein (CRP) and interleukin-6 (IL-6) in chronic Spinal Cord Injury (SCI).Study design: Prospective cohort study.Setting: Community dwelling individuals with SCI.Participants: 338 (278 male, 60 female) community dwelling individuals with chronic SCI (≥1-year post-injury).Interventions: None.Main outcome measures: CRP and IL-6 levels were quantified by ultra-sensitive ELISA assay. General linear models were used to assess associations between various clinical and demographic factors and CRP and IL-6 levels.Results: There were 50 active ibuprofen users and 288 non-users. After adjusting for clinical and demographic factors, ibuprofen users had significantly lower CRP levels (2.3 mg/L versus 3.5 mg/L, P = 0.04) and IL-6 levels (3.2 pg/ml versus 4.0 pg/ml, P = 0.04) compared to nonusers.Conclusions: Our study suggests that self-reported ibuprofen use may be negatively associated with CRP and IL-6 levels in chronic SCI after adjusting for known confounding factors, and suggests ibuprofen use may be an important, potential variable to consider in future studies focused on systemic inflammation in SCI. Future prospective studies require assessing frequency, duration, and dosage-dependent effects of ibuprofen on systemic markers of inflammation in chronic SCI. These findings may support future clinical trials to determine safety and efficacy of ibuprofen treatment for various outcomes in chronic SCI.

Obesity-Related Indices Are Associated with Longitudinal Changes in Lung Function: A Large Taiwanese Population Follow-Up Study

The global pandemic of obesity and the increasing incidence of chronic respiratory diseases are growing health concerns. The association between obesity and pulmonary function is uncertain. Therefore, this study aimed to explore associations between changes in lung function and obesity-related indices in a large longitudinal study. A total of 9059 participants with no personal histories of asthma, smoking, bronchitis, or emphysema were enrolled from the Taiwan Biobank and followed for 4 years. Lung function was assessed using spirometry measurements including forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC). Changes in FEV1/FVC (∆FEV1/FVC) between baseline and follow-up were calculated. The following obesity-related indices were studied: lipid accumulation product (LAP), body roundness index (BRI), conicity index (CI), body adiposity index (BAI), abdominal volume index (AVI), body mass index (BMI), waist–hip ratio (WHR), and waist-to-height ratio (WHtR). In multivariable analysis, the subjects with high BMI (p < 0.001), WHR (p < 0.001), WHtR (p < 0.001), LAP (p = 0.002), BRI (p < 0.001), CI (p = 0.005), BAI (p < 0.001), and AVI (p < 0.001) were significantly associated with a high baseline FEV1/FVC. After 4 years of follow-up, the subjects with high BMI (p < 0.001), WHR (p < 0.001), WHtR (p < 0.001), LAP (p = 0.001), BRI (p < 0.001), CI (p = 0.002), BAI (p < 0.001), and AVI (p < 0.001) were significantly associated with a low △FEV1/FVC. High obesity-related index values were associated with better baseline lung function and a rapid decrease in lung function at follow-up.

MicroRNA-7 promotes motor function recovery following spinal cord injury in mice

Spinal cord injury (SCI) is a devastating neurological condition for which there are no effective therapies. Following an initial injury, there is a cascade of multiple downstream events termed secondary injury. Thus, therapeutic approaches targeting a single pathway may not offer the best solution for treating SCI. One of the most attractive properties of microRNAs (miR) as potential therapeutics is that they are highly effective in regulating complex biological pathways by targeting multiple genes and pathways. The current study investigated the role of miR-7-5p (miR-7), which was previously shown to have neuroprotective functions, in promoting motor function recovery following SCI. We used an adeno-associated virus 1 (AAV1) vector to deliver the gene encoding miR-7 to the spinal cord of adult mice and found that this virus was mainly transduced into the neurons of the spinal cord. Transduction of AAV1-miR-7 improved hindlimb locomotor function following SCI over an 8-week observation period. This improvement was accompanied by reduced neuronal loss in the lesion. In addition, the beneficial effect of miR-7 was associated with enhanced levels of TH-positive axons in the lesion. Taken together, we suggest that miR-7 improves motor function recovery after SCI by protecting neuronal death and increasing axon levels. These findings suggest that miR-7 could be developed as a potential treatment for SCI in human.

Circulating PAMM, a novel antioxidant and anti-inflammatory protein, is elevated in acute SCI

Background

Peroxiredoxin activated in M-CSF stimulated monocytes (PAMM) is a novel protein produced by adipocytes with putative redox regulatory and anti-inflammatory properties. Because acute spinal cord injury (SCI) is associated with oxidative stress and neuroinflammation and because PAMM can be detected in systemic circulation, we hypothesized that acute neuro-trauma might induce changes in circulating PAMM expression. Specifically, we hypothesized that PAMM levels might vary based on the presence or absence of acute, traumatic SCI. We therefore investigated circulating PAMM levels in adults with and without acute traumatic SCI.

Methods

We studied 105 men and women (54 with SCI and 51 without SCI). Participants with SCI were admitted for acute rehabilitation within 1 month after injury. Serum samples were obtained during hospitalization and stored at − 80 °C until batch analysis. Total PAMM was quantified by ELISA assay (MyBiosource, Cat. No: MBS9327247) with a detection limit of 0.25 ng/ml. Separate multivariate models including age, BMI, and injury severity were assessed to determine significant clinical predictors of change in PAMM levels.

Results

When adjusting for BMI, age, and gender, mean change in PAMM levels were greatest in participants with motor complete SCI compared to able-bodied (1.65 ng/ml versus 0.94 ng/ml, p = 0.003). This model explained 26% of the variation in change in circulating PAMM levels.

Conclusions

Our results suggest that PAMM may be a novel biomarker of neurological injury or of native anti-inflammatory responses to neurological injury. More work is needed to establish the role of PAMM and other adipocyte-derived factors in the acute response to neurotrauma.

Cervical spinal stenosis and risk of pulmonary dysfunction

Background:

Cervical spinal stenosis (CSS) is defined as an abnormal narrowing of the cervical spinal canal. The essential clinical challenges with CSS are altered cervical spinal cord function and cervical radiculopathy. Phrenic nerve palsy leading to hemidiaphragmatic paresis may be a temporary or persistent phenomenon after cervical cord injury and CSS.

Objective:

The objective of the study is to elucidate the potential effect of CSS on the pulmonary functions.

Methods:

This is a case–control study which included 40 patients divided into two groups 30 females and 10 males patients with CSS (C5 and above) and 60 healthy volunteers with body mass index (BMI) <30 Kg/m². Pulmonary function tests have been done for all the patients.

Results:

The present study showed that VC in expiration (VC EX%), forced expiratory volume (FEV%), forced vital capacity % (FVC%), PEF%, and mean voluntary ventilation % (MVV%), were low in patients CSS compared with the control groups; P < 0.001, P < 0.001, P < 0.001, P = 0.042, and P = 0.037, respectively. As well, VC EX%, FEV1%, and FVC% were low in male patients in comparison to the controls P < 0.05. Besides, there were no significant differences regarding age, BMI, VC in inspiration (VC IN%), PEF%, FEV1/FVC%, and MVV%. Moreover, VC EX%, FEV1%, and FVC% were low in female patients compared to the controls, P < 0.001. Whereas, there were no significant differences that had been identified between female patients and female controls regarding age, BMI, VC IN%, PEF%, FEV1/FVC%, and MVV%. On the other hand, weight, height, and MVV% were low in female patients compared to male patients, P < 0.001.

Conclusion:

Chronic CSS leads to subclinical pulmonary dysfunction due to the involvement of the phrenic nerve. FEV% is the most sensitive parameter in the detection these disorders.

Fibrotic and apoptotic markers alteration in ovariectomised rats: addition of swimming training preserves lung architecture

CONTEXT

The important role of exercise in pulmonary function during menopause is not well known. Oestrogen deficiency in ageing female mice is accompanied by increase in apoptotic markers such as caspase3 in the lung.

OBJECTIVE

The present study was designed to investigate whether swimming training will ameliorate fibrosis and apoptosis resolution in the ovariectomy-induced lung injury rats.

MATERIAL AND METHOD

Thirty female rats were assigned to three groups (n = 10 in each group): sham; rats underwent bilateral laparotomy without ovariectomy, OVX; rats underwent bilateral ovariectomy, OVX.Exe; ovariectomised rats that underwent swimming training for eight weeks. At the end of eight weeks, the lungs were harvested and protein expressions in whole lung tissues were analysed by western blotting technique.

RESULT

Analysis of proteins expression in the lung showed significant differences between exercise and ovariectomised group (p < .05).

CONCLUSION

The present study indicates strong potential of exercise in experimental oestrogen deficiency-induced lung damage.

FEV1 and FVC and systemic inflammation in a spinal cord injury cohort

Background

Systemic inflammation has been associated with reduced pulmonary function in individuals with and without chronic medical conditions. Individuals with chronic spinal cord injury (SCI) have clinical characteristics that promote systemic inflammation and also have reduced pulmonary function. We sought to assess the associations between biomarkers of systemic inflammation with pulmonary function in a chronic SCI cohort, adjusting for other potential confounding factors.

Methods

Participants (n = 311) provided a blood sample, completed a respiratory health questionnaire, and underwent spirometry. Linear regression methods were used to assess cross-sectional associations between plasma C-reactive protein (CRP) and interleukin-6 (IL-6) with forced expiratory volume in one second (FEV₁), forced vital capacity (FVC), and FEV₁/FVC.

Results

There were statistically significant inverse relationships between plasma CRP and IL-6 assessed in quartiles or continuously with FEV₁ and FVC. In fully adjusted models, each interquartile range (5.91 mg/L) increase in CRP was associated with a significant decrease in FEV₁ (−55.85 ml; 95% CI: -89.21, −22.49) and decrease in FVC (−65.50 ml; 95% CI: -106.61, −24.60). There were similar significant findings for IL-6. There were no statistically significant associations observed with FEV₁/FVC.

Conclusion

Plasma CRP and IL-6 in individuals with chronic SCI are inversely associated with FEV₁ and FVC, independent of SCI level and severity of injury, BMI, and other covariates. This finding suggests that systemic inflammation associated with chronic SCI may contribute to reduced pulmonary function.

Electronic supplementary material

The online version of this article (doi:10.1186/s12890-017-0459-6) contains supplementary material, which is available to authorized users.

Menopause Is Associated with Accelerated Lung Function Decline

RATIONALE

Menopause is associated with changes in sex hormones, which affect immunity, inflammation, and osteoporosis and may impair lung function. Lung function decline has not previously been investigated in relation to menopause.

OBJECTIVES

To study whether lung function decline, assessed by FVC and FEV₁, is accelerated in women who undergo menopause.

METHODS

The population-based longitudinal European Community Respiratory Health Survey provided serum samples, spirometry, and questionnaire data about respiratory and reproductive health from three study waves (n = 1,438). We measured follicle-stimulating hormone and luteinizing hormone and added information on menstrual patterns to determine menopausal status using latent class analysis. Associations with lung function decline were investigated using linear mixed effects models, adjusting for age, height, weight, pack-years, current smoking, age at completed full-time education, spirometer, and including study center as random effect.

MEASUREMENTS AND MAIN RESULTS

Menopausal status was associated with accelerated lung function decline. The adjusted mean FVC decline was increased by -10.2 ml/yr (95% confidence interval [CI], -13.1 to -7.2) in transitional women and -12.5 ml/yr (95% CI, -16.2 to -8.9) in post-menopausal women, compared with women menstruating regularly. The adjusted mean FEV₁ decline increased by -3.8 ml/yr (95% CI, -6.3 to -2.9) in transitional women and -5.2 ml/yr (95% CI, -8.3 to -2.0) in post-menopausal women.

CONCLUSIONS

Lung function declined more rapidly among transitional and post-menopausal women, in particular for FVC, beyond the expected age change. Clinicians should be aware that respiratory health often deteriorates during reproductive aging.

Multiple organ dysfunction and systemic inflammation after spinal cord injury: a complex relationship

Spinal cord injury (SCI) is a devastating event that results in significant physical disabilities for affected individuals. Apart from local injury within the spinal cord, SCI patients develop a variety of complications characterized by multiple organ dysfunction or failure. These disorders, such as neurogenic pain, depression, lung injury, cardiovascular disease, liver damage, kidney dysfunction, urinary tract infection, and increased susceptibility to pathogen infection, are common in injured patients, hinder functional recovery, and can even be life threatening. Multiple lines of evidence point to pathological connections emanating from the injured spinal cord, post-injury systemic inflammation, and immune suppression as important multifactorial mechanisms underlying post-SCI complications. SCI triggers systemic inflammatory responses marked by increased circulation of immune cells and pro-inflammatory mediators, which result in the infiltration of inflammatory cells into secondary organs and persistence of an inflammatory microenvironment that contributes to organ dysfunction. SCI also induces immune deficiency through immune organ dysfunction, resulting in impaired responsiveness to pathogen infection. In this review, we summarize current evidence demonstrating the relevance of inflammatory conditions and immune suppression in several complications frequently seen following SCI. In addition, we highlight the potential pathways by which inflammatory and immune cues contribute to multiple organ failure and dysfunction and discuss current anti-inflammatory approaches used to alleviate post-SCI complications. A comprehensive review of this literature may provide new insights into therapeutic strategies against complications after SCI by targeting systemic inflammation.