Development and Application of Extraction Methods for LC-MS Quantification of Microcystins in Liver Tissue

A method was developed to extract and quantify microcystins (MCs) from mouse liver with limits of quantification (LOQs) lower than previously reported. MCs were extracted from 40-mg liver samples using 85:15 (v:v) CH₃CN:H₂O containing 200 mM ZnSO₄ and 1% formic acid. Solid-phase extraction with a C18 cartridge was used for sample cleanup. MCs were detected and quantified using HPLC-orbitrap-MS with simultaneous MS/MS detection of the 135.08 m/z fragment from the conserved Adda amino acid for structural confirmation. The method was used to extract six MCs (MC-LR, MC-RR, MC-YR, MC-LA, MC-LF, and MC-LW) from spiked liver tissue and the MC-LR cysteine adduct (MC-LR-Cys) created by the glutathione detoxification pathway. Matrix-matched internal standard calibration curves were constructed for each MC (R² ≥ 0.993), with LOQs between 0.25 ng per g of liver tissue (ng/g) and 0.75 ng/g for MC-LR, MC-RR, MC-YR, MC-LA, and MC-LR-Cys, and 2.5 ng/g for MC-LF and MC-LW. The protocol was applied to extract and quantify MC-LR and MC-LR-Cys from the liver of mice that had been gavaged with 50 µg or 100 µg of MC-LR per kg bodyweight and were euthanized 2 h, 4 h, or 48 h after final gavage. C57Bl/6J (wild type, control) and Lepr^db/J (experiment) mice were used as a model to study non-alcoholic fatty liver disease. The Lepr^db/J mice were relatively inefficient in metabolizing MC-LR into MC-LR-Cys, which is an important defense mechanism against MC-LR exposure. Trends were also observed as a function of MC-LR gavage amount and time between final MC-LR gavage and euthanasia/organ harvest.

Renal Fibrosis Is Significantly Attenuated Following Targeted Disruption of Cd40 in Experimental Renal Ischemia

Background

Renal artery stenosis is a common cause of renal ischemia, contributing to the development of chronic kidney disease. To investigate the role of local CD40 expression in renal artery stenosis, Goldblatt 2‐kidney 1‐clip surgery was performed on hypertensive Dahl salt‐sensitive rats (S rats) and genetically modified S rats in which CD40 function is abolished (Cd40^mutant).

Methods and Results

Four weeks following the 2‐kidney 1‐clip procedure, Cd40^mutant rats demonstrated significantly reduced blood pressure and renal fibrosis in the ischemic kidneys compared with S rat controls. Similarly, disruption of Cd40 resulted in reduced 24‐hour urinary protein excretion in Cd40^mutant rats versus S rat controls (46.2±1.9 versus 118.4±5.3 mg/24 h; P<0.01), as well as protection from oxidative stress, as indicated by increased paraoxonase activity in Cd40^mutant rats versus S rat controls (P<0.01). Ischemic kidneys from Cd40^mutant rats demonstrated a significant decrease in gene expression of the profibrotic mediator, plasminogen activator inhibitor‐1 (P<0.05), and the proinflammatory mediators, C‐C motif chemokine ligand 19 (P<0.01), C‐X‐C Motif Chemokine Ligand 9 (P<0.01), and interleukin‐6 receptor (P<0.001), compared with S rat ischemic kidneys, as assessed by quantitative PCR assay. Reciprocal renal transplantation documented that CD40 exclusively expressed in the kidney contributes to ischemia‐induced renal fibrosis. Furthermore, human CD40‐knockout proximal tubule epithelial cells suggested that suppression of CD40 signaling significantly inhibited expression of proinflammatory and ‐fibrotic genes.

Conclusions

Taken together, our data suggest that activation of CD40 induces a significant proinflammatory and ‐fibrotic response and represents an attractive therapeutic target for treatment of ischemic renal disease.

Intra-articular Steroids vs Saline for Lumbar Z-Joint Pain: A Prospective, Randomized, Double-Blind Placebo-Controlled Trial

OBJECTIVE

To determine if intra-articular (IA) injection of corticosteroids is effective in reducing the need for radiofrequency ablation (RFA) in those with dual comparative medial branch block (MBB)-confirmed lumbar z-joint pain.

DESIGN

This was a randomized, double blind, placebo-controlled study.

SETTING

Two academic medical centers.

SUBJECTS

Fifty-six consecutive subjects who had ≥80% pain relief during an initial screening MBB were recruited.

METHODS

Patients received a second confirmatory MBB and concurrent IA injection of either corticosteroid or saline per randomization. Twenty-nine of 56 received intra-articular corticosteroid (triamcinolone 20 mg), of whom 24 also had a positive confirmatory MBB per Spine Interventional Society guidelines, with ≥80% pain relief from both MBBs. Twenty-seven of 56 received IA saline into the z-joint during the confirmatory MBB, of whom 22 also had a positive confirmatory MBB. The primary outcome measure was the categorical need for RFA due to insufficient pain relief with intra-articular injection, and the secondary outcome was time to RFA.

RESULTS

There was no statistically significant difference in the need for an RFA between the groups (16/24 steroid, 67%, 95% confidence interval [CI] = 47-82%) vs 15/22 saline (68%, 95% CI = 47-84%, P = 1.00). The average time to RFA was also not different, at 6.00 weeks for steroids vs 6.55 weeks for saline (P = 0.82).

CONCLUSIONS

Intra-articular corticosteroids were not effective in reducing the need for or the time to a radiofrequency ablation of the medial branches in those with dual MBB-confirmed lumbar z-joint pain.

Epithelial and Endothelial Adhesion of Immune Cells Is Enhanced by Cardiotonic Steroid Signaling Through Na+/K+-ATPase-α-1

Background

Recent studies have highlighted a critical role for a group of natriuretic hormones, cardiotonic steroid (CTS), in mediating renal inflammation and fibrosis associated with volume expanded settings, such as chronic kidney disease. Immune cell adhesion is a critical step in the inflammatory response; however, little is currently understood about the potential regulatory role of CTS signaling in this setting. Herein, we tested the hypothesis that CTS signaling through Na⁺/K⁺‐ATPase α‐1 (NKA α‐1) enhances immune cell recruitment and adhesion to renal epithelium that ultimately advance renal inflammation.

Methods and Results

We demonstrate that knockdown of the α‐1 isoform of Na/K‐ATPase causes a reduction in CTS‐induced macrophage infiltration in renal tissue as well reduces the accumulation of immune cells in the peritoneal cavity in vivo. Next, using functional adhesion assay, we demonstrate that CTS‐induced increases in the adhesion of macrophages to renal epithelial cells were significantly diminished after reduction of NKA α‐1 in either macrophages or renal epithelial cells as well after inhibition of NKA α‐1‐Src signaling cascade with a specific peptide inhibitor, pNaKtide in vitro. Finally, CTS‐induced expression of adhesion markers in both endothelial and immune cells was significantly inhibited in an NKA α‐1‐Src signaling dependent manner in vitro.

Conclusions

These findings suggest that CTS potentiates immune cell migration and adhesion to renal epithelium through an NKA α‐1–dependent mechanism; our new findings suggest that pharmacological inhibition of this feed‐forward loop may be useful in the treatment of renal inflammation associated with renal disease.

Pain and Functional Outcomes After Sacroiliac Joint Injection with Anesthetic and Corticosteroid at Six Months, Stratified by Anesthetic Response and Physical Exam Maneuvers

OBJECTIVE

To evaluate sacroiliac joint (SIJ) injection outcomes with local anesthetic and corticosteroid.

DESIGN

Prospective cohort.

SETTING

Single academic medical center.

METHODS

Thirty-four patients referred for SIJ injection with a clinical diagnosis of SIJ pain underwent injections with 1:1 mixture of 2% lidocaine and triamcinolone 40 mg/mL. Pain provocation physical exam (PE) maneuvers were recorded immediately before and after injection. Outcome measures at two to four weeks and six months included pain numeric rating scale (NRS) and Oswestry Disability Index (ODI).

RESULTS

For the analysis of outcomes by the overall group (not stratified by PE and/or anesthetic block), a 58.8% (95% confidence interval [CI] = +/-16.5%) ≥2 NRS reduction, a 32.4% (95% CI = +/-15.7%) ≥50% NRS reduction, and a 38.2% (95% CI = +/-16.3%) ≥30% ODI reduction were observed at two to four weeks, with similar improvements at six months. Outcomes stratified based on pre-injection PE did not reveal significant differences at either time point. The stratification based on the presence of 100% postinjection anesthetic response demonstrated a significant difference at two to four weeks for ≥50% NRS improvement. The true positive/true negative group (TP/TN) stratification demonstrated a significant difference for ≥50% NRS improvement at two to four weeks, whereas six-month outcomes for TP/TN demonstrated significant differences for ≥50% NRS and ≥30% ODI improvement. An increased injection response was observed with stratification of patients more likely to have true SIJ pain (i.e., TP), with TP/TN stratification demonstrating a 75% (95% CI = +/-30.0%) ≥2 NRS improvement and a 62.5% (95% CI = +/-33.5%) improvement of ≥50% NRS and ≥30% ODI for the TP group at two to four weeks, with similar results at six months.

CONCLUSIONS

SIJ steroid injection based on referral clinical diagnosis is unlikely to demonstrate true injection efficacy, and more specific selection criteria are warranted.

Hyperglycemia induces key genetic and phenotypic changes in human liver epithelial HepG2 cells which parallel the Leprdb/J mouse model of non-alcoholic fatty liver disease (NAFLD)

Non-alcoholic fatty liver disease (NAFLD) is a growing global health concern. With a propensity to progress towards non-alcoholic steatohepatitis (NASH), cirrhosis, and hepatocellular carcinoma, NAFLD is an important link amongst a multitude of comorbidities including obesity, diabetes, and cardiovascular and kidney disease. As several in vivo models of hyperglycemia and NAFLD are employed to investigate the pathophysiology of this disease process, we aimed to characterize an in vitro model of hyperglycemia that was amenable to address molecular mechanisms and therapeutic targets at the cellular level. Utilizing hyperglycemic cell culturing conditions, we induced steatosis within a human hepatocyte cell line (HepG2 cells), as confirmed by electron microscopy. The deposition and accumulation of lipids within hyperglycemic HepG2 cells is significantly greater than in normoglycemic cells, as visualized and quantified by Nile red staining. Alanine aminotransferase (ALT) and alkaline phosphatase (ALP), diagnostic biomarkers for liver damage and disease, were found to be upregulated in hyperglycemic HepG2 cells as compared with normoglycemic cells. Suppression of CEACAM1, GLUT2, and PON1, and elevation of CD36, PCK1, and G6PK were also found to be characteristic in hyperglycemic HepG2 cells compared with normoglycemic cells, suggesting insulin resistance and NAFLD. These in vitro findings mirror the characteristic genetic and phenotypic profile seen in Lepr^db/J mice, a well-established in vivo model of NAFLD. In conclusion, we characterize an in vitro model displaying several key genetic and phenotypic characteristics in common with NAFLD that may assist future studies in addressing the molecular mechanisms and therapeutic targets to combat this disease.

CD36 Enhances Vascular Smooth Muscle Cell Proliferation and Development of Neointimal Hyperplasia

Objective- Dysregulated proliferation of vascular smooth muscle cells (VSMC) plays an essential role in neointimal hyperplasia. CD36 functions critically in atherogenesis and thrombosis. We hypothesize that CD36 regulates VSMC proliferation and contributes to the development of obstructive vascular diseases. Approach and Results- We found by immunofluorescent staining that CD36 was highly expressed in human vessels with obstructive diseases. Using guidewire-induced carotid artery injury and shear stress-induced intima thickening models, we compared neointimal hyperplasia in Apoe^-/-, Cd36^-/- /Apoe^-/-, and CD36 specifically deleted in VSMC (VSMC ^cd36-/-) mice. CD36 deficiency, either global or VSMC-specific, dramatically reduced injury-induced neointimal thickening. Correspondingly, carotid artery blood flow was significantly increased in Cd36^-/- /Apoe^-/- compared with Apoe^-/- mice. In cultured VSMCs from thoracic aorta of wild-type and Cd36^-/- mice, we found that loss of CD36 significantly decreased serum-stimulated proliferation and increased cell populations in S phase, suggesting that CD36 is necessary for VSMC S/G2-M-phase transition. Treatment of VSMCs with a TSR (thrombospondin type 1 repeat) peptide significantly increased wild-type, but not Cd36^-/- VSMC proliferation. TSR or serum treatment significantly increased cyclin A expression in wild-type, but not in Cd36^-/- VSMCs. STAT3 (signal transducer and activator of transcription), which reportedly enhances both VSMC differentiation and maturation, was higher in Cd36^-/- VSMCs. CD36 deficiency significantly decreased expression of Col1A1 (type 1 collagen A1 chain) and TGF-β1 (transforming growth factor beta 1), and increased expression of contractile proteins, including calponin 1 and smooth muscle α actin, and dramatically increased cell contraction. Conclusions- CD36 promotes VSMC proliferation via upregulation of cyclin A expression that contributes to the development of neointimal hyperplasia, collagen deposition, and obstructive vascular diseases.

Na/K-ATPase/src complex mediates regulation of CD40 in renal parenchyma

Background

Recent studies have highlighted a critical role for CD40 in the pathogenesis of renal injury and fibrosis. However, little is currently understood about the regulation of CD40 in this setting.

Methods

We use novel Na/K-ATPase cell lines and inhibitors in order to demonstrate the regulatory function of Na/K-ATPase with regards to CD40 expression and function. We utilize 5/6 partial nephrectomy as well as direct infusion of a Na/K-ATPase ligand to demonstrate this mechanism exists in vivo.

Results

We demonstrate that knockdown of the α1 isoform of Na/K-ATPase causes a reduction in CD40 while rescue of the α1 but not the α2 isoform restores CD40 expression in renal epithelial cells. Second, because the major functional difference between α1 and α2 is the ability of α1 to form a functional signaling complex with Src, we examined whether the Na/K-ATPase/Src complex is important for CD40 expression. We show that a gain-of-Src binding α2 mutant restores CD40 expression while loss-of-Src binding α1 reduces CD40 expression. Furthermore, loss of a functional Na/K-ATPase/Src complex also disrupts CD40 signaling. Importantly, we show that use of a specific Na/K-ATPase/Src complex antagonist, pNaKtide, can attenuate cardiotonic steroid (CTS)-induced induction of CD40 expression in vitro.

Conclusions

Because the Na/K-ATPase/Src complex is also a key player in the pathogenesis of renal injury and fibrosis, our new findings suggest that Na/K-ATPase and CD40 may comprise a pro-fibrotic feed-forward loop in the kidney and that pharmacological inhibition of this loop may be useful in the treatment of renal fibrosis.

Building a Collaborative Model of Sacroiliac Joint Dysfunction and Pelvic Girdle Pain to Understand the Diverse Perspectives of Experts

BACKGROUND

Pelvic girdle pain (PGP) and sacroiliac joint (SIJ) dysfunction/pain are considered frequent contributors to low back pain (LBP). Like other persistent pain conditions, PGP is increasingly recognized as a multifactorial problem involving biological, psychological, and social factors. Perspectives differ between experts and a diversity of treatments (with variable degrees of evidence) have been utilized.

OBJECTIVE

To develop a collaborative model of PGP that represents the collective view of a group of experts. Specific goals were to analyze structure and composition of conceptual models contributed by participants, to aggregate them into a metamodel, to analyze the metamodel's composition, and to consider predicted efficacy of treatments.

DESIGN

To develop a collaborative model of PGP, models were generated by invited individuals to represent their understanding of PGP using fuzzy cognitive mapping (FCM). FCMs involved proposal of components related to causes, outcomes, and treatments for pain, disability, and quality of life, and their connections. Components were classified into thematic categories. Weighting of connections was summed for components to judge their relative importance. FCMs were aggregated into a metamodel for analysis of the collective opinion it represented and to evaluate expected efficacy of treatments.

RESULTS

From 21 potential contributors, 14 (67%) agreed to participate (representing six disciplines and seven countries). Participants' models included a mean (SD) of 22 (5) components each. FCMs were refined to combine similar terms, leaving 89 components in 10 categories. Biomechanical factors were the most important in individual FCMs. The collective opinion from the metamodel predicted greatest efficacy for injection, exercise therapy, and surgery for pain relief.

CONCLUSIONS

The collaborative model of PGP showed a bias toward biomechanical factors. Most efficacious treatments predicted by the model have modest to no evidence from clinical trials, suggesting a mismatch between opinion and evidence. The model enables integration and communication of the collection of opinions on PGP.

Circulating Lactonase Activity but Not Protein Level of PON-1 Predicts Adverse Outcomes in Subjects with Chronic Kidney Disease

The burden of cardiovascular disease and death in chronic kidney disease (CKD) outpaces that of the other diseases and is not adequately described by traditional risk factors alone. Diminished activity of paraoxonase (PON)-1 is associated with increased oxidant stress, a common feature underlying the pathogenesis of CKD. We aimed to assess the prognostic value of circulating PON-1 protein and PON lactonase activity on adverse clinical outcomes across various stages and etiologies of CKD. Circulating PON-1 protein levels and PON lactonase activity were measured simultaneously in patients with CKD as well as a cohort of apparently healthy non-CKD subjects. Both circulating PON-1 protein levels and PON lactonase activity were significantly lower in CKD patients compared to the non-CKD subjects. Similarly, across all stages of CKD, circulating PON-1 protein and PON lactonase activity were significantly lower in patients with CKD compared to the non-CKD controls. Circulating PON lactonase activity, but not protein levels, predicted future adverse clinical outcomes, even after adjustment for traditional risk factors. The combination of lower circulating protein levels and higher activity within the CKD subjects were associated with the best survival outcomes. These findings demonstrate that diminished circulating PON lactonase activity, but not protein levels, predicts higher risk of future adverse clinical outcomes in patients with CKD.

Proinflammatory Effects of Cardiotonic Steroids Mediated by NKA α-1 (Na+/K+-ATPase α-1)/Src Complex in Renal Epithelial Cells and Immune Cells

Cardiotonic steroids (CTSs) are NKA α-1 (Na⁺/K⁺-ATPase α-1) ligands that are increased in volume expanded states and associated with cardiac and renal diseases. Although initiation and resolution of inflammation is an important component of cellular injury and repair in renal disease, it is unknown whether CTS activation of NKA α-1 signaling in this setting regulates this inflammatory response. On this background, we hypothesized that CTS signaling through the NKA α-1-Src kinase complex promotes a proinflammatory response in renal epithelial and immune cells. First, we observed that the CTS telocinobufagin activated multiple proinflammatory cytokines/chemokines in renal epithelial cells, and these effects were attenuated after either NKA α-1 knockdown or with a specific inhibitor of the NKA α-1-Src kinase complex (pNaKtide). Similar findings were observed in immune cells, where we demonstrated that while telocinobufagin induced both oxidative burst and enhanced Nuclear factor kappa-light-chain-enhancer of activated B cells activation in macrophages ( P<0.05), the effects were abolished in NKA α-1^+/- macrophages or by pretreatment with pNaKtide or the Src inhibitor PP2 ( P<0.01). In a series of in vivo studies, we found that 5/6th partial nephrectomy induced significantly less oxidative stress in the remnant kidney of NKA α-1^+/- versus wild-type mice. Similarly, 5/6th partial nephrectomy yielded decreased levels of the urinary oxidative stress marker 8-Oxo-2'-deoxyguanosine in NKA α-1^+/- versus wild-type mice. Finally, we found that in vivo inhibition of the NKA α-1-Src kinase complex with pNaKtide significantly inhibited renal proinflammatory gene expression after 5/6th partial nephrectomy. These findings suggest that the NKA α-1-Src kinase complex plays a central role in regulating the renal inflammatory response induced by elevated CTS both in vitro and in vivo.

Prevalence of low back pain among athletes: A systematic review

BACKGROUND

The prevalence of low back pain (LBP) in athletes across a variety of time frames and sports is not known.

OBJECTIVES

To systematically collate and appraise studies on the prevalence of LBP in athletes and stratify by point, one year and life-time prevalence.

METHODS

A comprehensive search was conducted in February 2016. The following sources were individually searched: PubMed (1950 to present), Ovid SP Medline (1950 to present), ISI (1982 to present) and Google Scholar; Surveys were included if they aimed to report the prevalence of LBP amongst the athletes. Two reviewers independently evaluated the methodological quality of the studies.

RESULTS

The literature search generated 4379 records. Title and/or abstracts were reviewed by two investigators and full-texts of 201 relevant articles were selected for further evaluation. Studies were included if they reported the prevalence of LBP in an athletic population (any level of participation in sports and any age range) and were written in English. Furthermore, to adequately assess the prevalence rate, studies had to report the number of athletes with LBP as a percentage of the total number of athletes. Studies that did not contain necessary data to calculate prevalence rate including case reports and non-original studies were excluded and 41 studies entered the bias assessment step. A bias assessment was applied to the methodology of 41 studies, and 36 with low to moderate risk for bias were included in this review. LBP in athletes was shown to have a point prevalence ranging from 10% to 67%, a one-year prevalence ranging from 17% to 94%, and a life-time prevalence ranging from 33% to 84%. The highest prevalence of LBP was found among skiers, floorball players and rowers and the lowest were found in shooters, golfers and triathletes.

CONCLUSION

Like general population, LBP is quite prevalent among athletes. There is a lack of sound data on the prevalence and mechanism of LBP in some popular sports such as volleyball, swimming and track and field. The lack of standardization of research methods and outcome measurement tools are significant problems in literature. Researchers need to use standard and internationally acceptable definitions for LBP and related functional disability. Investigators are encouraged to conduct epidemiologic studies, along with search for possible mechanism of LBP, by recruitment of large sample population of the athletes who are selected through randomization of the national population and adopt recent recommendations for a standard definition of LBP.

Development and applications of solid-phase extraction and liquid chromatography-mass spectrometry methods for quantification of microcystins in urine, plasma, and serum

The protocols for solid-phase extraction (SPE) of six microcystins (MCs; MC-LR, MC-RR, MC-LA, MC-LF, MC-LW, and MC-YR) from mouse urine, mouse plasma, and human serum are reported. The quantification of those MCs in biofluids was achieved using HPLC-orbitrap-MS in selected-ion monitoring (SIM) mode, and MCs in urine samples were also quantified by ultra-HPLC-triple quadrupole-tandem mass spectrometry (UHPLC-QqQ-MS/MS) in multiple reaction monitoring (MRM) mode. Under optimal conditions, the extraction recoveries of MCs from samples spiked at two different concentrations (1 μg/L and 10 μg/L) ranged from 90.4% to 104.3% with relative standard deviations (RSDs) ≤ 4.7% for mouse urine, 90.4-106.9% with RSDs ≤ 6.3% for mouse plasma, and 90.0-104.8% with RSDs ≤ 5.0% for human serum. Matrix-matched internal standard calibration curves were linear with R2 ≥ 0.9950 for MC-LR, MC-RR and MC-YR, and R2 ≥ 0.9883 for MC-LA, MC-LF, and MC-LW. The limits of quantification (LOQs) in spiked urine samples were ∼0.13 μg/L for MC-LR, MC-RR, and MC-YR, and ∼0.50 μg/L for MC-LA, MC-LF, and MC-LW, while the LOQs in spiked plasma and serum were ∼0.25 μg/L for MC-LR, MC-RR, and MC-YR, and ∼1.00 μg/L for MC-LA, MC-LF, and MC-LW. The developed methods were applied in a proof-of-concept study to quantify urinary and blood concentrations of MC-LR after oral administration to mice. The urine of mice administered 50 μg of MC-LR per kg bodyweight contained on average 1.30 μg/L of MC-LR (n = 8), while mice administered 100 μg of MC-LR per kg bodyweight had average MC-LR concentration of 2.82 μg/L (n = 8). MC-LR was also quantified in the plasma of the same mice. The results showed that increased MC-LR dosage led to larger urinary and plasma MC-LR concentrations and the developed methods were effective for the quantification of MCs in mouse biofluids.

Cardiotonic Steroids and the Sodium Trade Balance: New Insights into Trade-Off Mechanisms Mediated by the Na⁺/K⁺-ATPase

In 1972 Neal Bricker presented the "trade-off" hypothesis in which he detailed the role of physiological adaptation processes in mediating some of the pathophysiology associated with declines in renal function. In the late 1990's Xie and Askari published seminal studies indicating that the Na⁺/K⁺-ATPase (NKA) was not only an ion pump, but also a signal transducer that interacts with several signaling partners. Since this discovery, numerous studies from multiple laboratories have shown that the NKA is a central player in mediating some of these long-term "trade-offs" of the physiological adaptation processes which Bricker originally proposed in the 1970's. In fact, NKA ligands such as cardiotonic steroids (CTS), have been shown to signal through NKA, and consequently been implicated in mediating both adaptive and maladaptive responses to volume overload such as fibrosis and oxidative stress. In this review we will emphasize the role the NKA plays in this "trade-off" with respect to CTS signaling and its implication in inflammation and fibrosis in target organs including the heart, kidney, and vasculature. As inflammation and fibrosis exhibit key roles in the pathogenesis of a number of clinical disorders such as chronic kidney disease, heart failure, atherosclerosis, obesity, preeclampsia, and aging, this review will also highlight the role of newly discovered NKA signaling partners in mediating some of these conditions.

Telocinobufagin, a Novel Cardiotonic Steroid, Promotes Renal Fibrosis via Na⁺/K⁺-ATPase Profibrotic Signaling Pathways

Cardiotonic steroids (CTS) are Na⁺/K⁺-ATPase (NKA) ligands that are elevated in volume-expanded states and associated with cardiac and renal dysfunction in both clinical and experimental settings. We test the hypothesis that the CTS telocinobufagin (TCB) promotes renal dysfunction in a process involving signaling through the NKA α-1 in the following studies. First, we infuse TCB (4 weeks at 0.1 µg/g/day) or a vehicle into mice expressing wild-type (WT) NKA α-1, as well as mice with a genetic reduction (~40%) of NKA α-1 (NKA α-1^+/−). Continuous TCB infusion results in increased proteinuria and cystatin C in WT mice which are significantly attenuated in NKA α-1^+/− mice (all p < 0.05), despite similar increases in blood pressure. In a series of in vitro experiments, 24-h treatment of HK2 renal proximal tubular cells with TCB results in significant dose-dependent increases in both Collagens 1 and 3 mRNA (2-fold increases at 10 nM, 5-fold increases at 100 nM, p < 0.05). Similar effects are seen in primary human renal mesangial cells. TCB treatment (100 nM) of SYF fibroblasts reconstituted with cSrc results in a 1.5-fold increase in Collagens 1 and 3 mRNA (p < 0.05), as well as increases in both Transforming Growth factor beta (TGFb, 1.5 fold, p < 0.05) and Connective Tissue Growth Factor (CTGF, 2 fold, p < 0.05), while these effects are absent in SYF cells without Src kinase. In a patient study of subjects with chronic kidney disease, TCB is elevated compared to healthy volunteers. These studies suggest that the pro-fibrotic effects of TCB in the kidney are mediated though the NKA-Src kinase signaling pathway and may have relevance to volume-overloaded conditions, such as chronic kidney disease where TCB is elevated.

Na/K-ATPase signaling mediates miR-29b-3p regulation and cardiac fibrosis formation in mice with chronic kidney disease

The Na/K-ATPase is an important membrane ion transporter and a signaling receptor that is essential for maintaining normal cell function. The current study examined the role of Na/K-ATPase signaling in regulating miR-29b-3p, an anti-fibrotic microRNA, in a mouse chronic kidney disease (CKD) model (5/6th partial nephrectomy or PNx). The results showed that CKD induced significant reduction of miR-29b-3p expression in the heart tissue by activation of Src and NFκB signaling in these animals. To demonstrate the role of Na/K-ATPase signaling, we also performed the PNx surgery on Na/K-ATPase α1 heterozygous (α1+/-) mice, which expresses ~40% less Na/K-ATPase α1 compared to their wild type littermates (WT) and exhibits deficiency in Na/K-ATPase signaling. We found that CKD did not significantly change the miR-29b-3p expression in heart tissue from the α1+/- animals. We also found that CKD failed to activate Src and NFκB signaling in these animals. Using isolated cardiac fibroblasts from α1+/- mice and their WT littermates, we showed that ouabain, a specific Na/K-ATPase ligand, induces decreased miR-29b-3p expression in fibroblasts isolated from WT mice, but had no effect in cells from α1+/- mice. Inhibition of NFκB by Bay11-7082 prevented ouabain-induced miR-29b-3p reduction in WT fibroblasts. To further confirm the in vivo effect of Na/K-ATPase signaling in regulation of miR-29b-3p and cardiac fibrosis in CKD animals, we used pNaKtide, a Src inhibiting peptide derived from the sequence of Na/K-ATPase, to block the activation of Na/K-ATPase signaling. The result showed that pNaKtide injection significantly increased miR-29b-3p expression and mitigated the CKD-induced cardiac fibrosis in these animals. These results clearly demonstrated that Na/K-ATPase signaling is an important mediator in CKD that regulates miR-29b-3p expression and cardiac fibrosis, which provides a novel target for regulation of miR-29b-3p in CKD. We also demonstrate that antagonizing Na/K-ATPase signaling by pNaKtide can reduce organ fibrosis through the stimulation of tissue miR-29b-3p expression.

Is There a Relationship Between Body Mass Index and Fluoroscopy Time During Cervical Interlaminar Epidural Steroid Injections?

Background

The challenge of obtaining medical imaging in individuals with higher body mass index (BMI) is described, but there is minimal data regarding the relationship between BMI and fluoroscopy time during cervical interlaminar epidural steroid injection (CIESI).

Objective

To determine the relationship between BMI and fluoroscopy time during CIESI.

Methods

Retrospective cohort study of patients who underwent fluoroscopically guided CIESI between January 2014 and February 2015 at an academic pain medicine center. Fluoroscopy time data were collected. Comparisons based on analysis of variance were made between patients with normal (<25.0 kg/m 2 ), overweight (25.0-29.9 kg/m 2 ), and obese (≥30.0 kg/m 2 ) BMI.

Results

Of 399 procedure encounters, 366 had documented BMI and fluoroscopy time data and were included for analysis. Mean age (± SD) in this cohort was 53 ± 13 years, including 189 females (52%) and 205 first-time injections. Mean fluoroscopy time for all injections was 18 ± 10 seconds. Separated by categorical BMI class, the mean fluoroscopy time was 18 ± 9 seconds for normal weight patients, 17 ± 10 seconds for overweight patients, and 20 ± 11 seconds for obese patients, respectively. Post hoc analysis showed that fluoroscopy time was significantly longer only in obese compared with overweight patients ( P  = 0.02). Trainee involvement and first-time vs repeat injection did not significantly alter fluoroscopy time ( P  = 0.17 and P  = 0.12, respectively).

Conclusions

The findings of this study indicate that BMI does not appear to have a clinically significant impact on fluoroscopy time during cervical interlaminar epidural steroid injection procedures. Future study is needed to directly quantify radiation exposure in patients and practitioners, as well as the associated health risk.

A minimum of 5-year follow-up after lumbar transforaminal epidural steroid injections in patients with lumbar radicular pain due to intervertebral disc herniation

BACKGROUND CONTEXT

Patients with lumbosacral radiculopathy from an intervertebral disc herniation are frequently treated by transforaminal epidural steroid injections (TFESIs). The long-term outcomes of these patients are poorly described.

PURPOSE

We aimed to determine the long-term outcomes for a homogenous group of patients with acute unilateral lumbar radicular pain due to single-level herniated nucleus after lumbar epidural steroid injection at ≥5 years.

DESIGN

This is a prospective cohort study.

PATIENT SAMPLE

Subjects enrolled into a previous reported multi-institutional randomized controlled trial, ≥18 years old with single leg radicular pain rating ≥4/10 for less than 6 months' duration, with radiographic imaging demonstrating an anatomically congruent single-level herniated nucleus pulposus.

OUTCOME MEASURES

Presence of recurrent or persistent pain, pain within the previous week, current opioid use for radicular symptoms, additional spine injections for radicular pain, progression to surgery, and unemployment due to pain as determined by independent phone interview at least 5 years after enrolment due to the initial pain complaint were the outcome measures.

METHODS

All patients initially underwent a single-level lumbar TFESIs due to failure of conservative care, but could elect to pursue surgical intervention or repeat injections through shared decision making with the treating physician when and if pain control was deemed inadequate. After ≥5 years, an independent assessor contacted the subjects by phone and performed a standardized interview to determine outcomes. Fisher exact test was used to compare outcomes for those who pursued versus those who did not pursue surgery.

RESULTS

During the recruitment period (December 2008 to December 2012), 78 subjects were enrolled. At 5 years, 39 (50%) of the 78 subjects were reachable for independent phone follow-up. Of these, 30 (76.9%, 95% confidence interval [CI] 61.7%-87.4%) had a history of recurrent pain since the initial TFESI. However, only 9 (23.1%, 95% CI 12.7%-38.3%) had current pain, while 3 (7.7%, 95% CI 2.7%-20.3%) were currently taking opioid medications. Nine (23.1%, 95% CI 12.7%-38.3%) had received additional TFESIs, and 19 (48.7%, 95% CI 33.9%-63.8%) had received surgery. Only 3 (7.7%, 95% CI 2.7%-20.3%) were unemployed due to related pain at time of follow-up. When comparing the group that had surgery versus those that did not, there were no differences in the rates of recurrent pain (16, 84.2% vs. 14, 70.0%, p=.81), current pain (6, 31.6% vs. 3, 15.0%, p=.47), opioid use (2, 10.5% vs. 1, 5.0%, p=1.00), rate of additional injections (6, 31.6% vs. 3, 15.0%, p=.47), or unemployment status (2, 10.5% vs. 1, 5.0%, p=1.00).

CONCLUSIONS

Despite a high success rate at 6 months, the majority of subjects experienced a recurrence of symptoms at some time during the subsequent 5 years. Fortunately, few reported current symptoms, and a small minority required additional injections, surgery, or opioid pain medications. Lumbar disc herniation is a disease that can be effectively treated in the short-term by TFESI or surgery, but long-term recurrence rates are high regardless of treatment received.