Neuropathic pain is caused by peripheral nerve injury (PNI). One hallmark symptom is allodynia (pain caused by normally innocuous stimuli), but its mechanistic underpinning remains elusive. Notably, whether selective stimulation of non-nociceptive primary afferent Aβ fibers indeed evokes neuropathic pain-like sensory and emotional behaviors after PNI is unknown, because of the lack of tools to manipulate Aβ fiber function in awake, freely moving animals. In this study, we used a transgenic rat line that enables stimulation of non-nociceptive Aβ fibers by a light-activated channel (channelrhodopsin-2; ChR2). We found that illuminating light to the plantar skin of these rats with PNI elicited pain-like withdrawal behaviors that were resistant to morphine. Light illumination to the skin of PNI rats increased the number of spinal dorsal horn (SDH) Lamina I neurons positive to activity markers (c-Fos and phosphorylated extracellular signal-regulated protein kinase; pERK). Whole-cell recording revealed that optogenetic Aβ fiber stimulation after PNI caused excitation of Lamina I neurons, which were normally silent by this stimulation. Moreover, illuminating the hindpaw of PNI rats resulted in activation of central amygdaloid neurons and produced an aversion to illumination. Thus, these findings provide the first evidence that optogenetic activation of primary afferent Aβ fibers in PNI rats produces excitation of Lamina I neurons and neuropathic pain-like behaviors that were resistant to morphine treatment. This approach may provide a new path for investigating circuits and behaviors of Aβ fiber-mediated neuropathic allodynia with sensory and emotional aspects after PNI and for discovering novel drugs to treat neuropathic pain.

Pharmacological blockade of CCR5 was effective in the treatment of the development and maintenance phases of neuropathic pain. Thus, CCR5 antagonists may be potential new drugs for the treatment of neuropathic pain.

Acute cardiorenal syndrome is a common complication of acute cardiovascular disease. Studies of acute kidney injury (AKI) to chronic kidney disease (CKD) transition, including patients suffering acute cardiovascular disease, report high rates of CKD development. Therefore, acute cardiorenal syndrome associates with CKD, but no study has established causation. To define this we used a murine cardiac arrest (CA) and cardiopulmonary resuscitation (CPR) model or sham procedure on male mice. CA was induced with potassium chloride while CPR consisted of chest compressions and epinephrine eight minutes later. Two weeks after AKI was induced by CA/CPR, the measured glomerular filtration rate (GFR) was not different from sham. However, after seven weeks the mice developed CKD, recapitulating clinical observations. One day, and one, two, and seven weeks after CA/CPR, the GFR was measured, and renal tissue sections were evaluated for various indices of injury and inflammation. One day after CA/CPR, acute cardiorenal syndrome was indicated by a significant reduction of the mean GFR (649 in sham, vs. 25 mL/min/ 100g in CA/CPR animals), KIM-1 positive tubules, and acute tubular necrosis. Renal inflammation developed, with F4/80 positive and CD3-positive cells infiltrating the kidney one day and one week after CA/CPR, respectively. Although there was functional recovery with normalization of GFR two weeks after CA/CPR, deposition of tubulointerstitial matrix proteins a-smooth muscle actin and fibrillin-1 progressed, along with a significantly reduced mean GFR (623 in sham vs. 409 mL/min/100g in CA/CPR animals), proteinuria, increased tissue transforming growth factor-b, and fibrosis establishing the development of CKD seven weeks after CA/CPR. Thus, murine CA/CPR, a model of acute cardiorenal syndrome, causes an AKI-CKD transition likely due to prolonged renal inflammation.

Background Rhabdomyolysis, the destruction of skeletal muscle, is a significant cause of acute kidney injury (AKI) and death in the context of natural disaster and armed conflict. Rhabdomyolysis may also initiate chronic kidney disease (CKD). Development of specific pharmacologic therapy is desirable because supportive care is nearly impossible in austere environments. Myoglobin, the principal cause of rhabdomyolysis-related AKI, undergoes megalin-mediated endocytosis in proximal tubule cells, a process that specifically injures these cells. Methods To investigate whether megalin is protective in a mouse model of rhabdomyolysis-induced AKI, we used male C57BL/6 mice and mice (14-32 weeks old) with proximal tubule-specific deletion of megalin. We used a well-characterized rhabdomyolysis model, injection of 50% glycerol in normal saline preceded by water deprivation. Results Inducible proximal tubule-specific deletion of megalin was highly protective in this mouse model of rhabdomyolysis-induced AKI. The megalin knockout mice demonstrated preserved glomerular filtration rate (GFR), reduced proximal tubule injury (as indicated by kidney injury molecule-1), and reduced renal apoptosis 24 hours after injury. These effects were accompanied by increased urinary myoglobin clearance. Unlike littermate controls, the megalin-deficient mice also did not develop progressive GFR decline and persistent new proteinuria. Administration of the pharmacologic megalin inhibitor cilastatin to wild-type mice recapitulated the renoprotective effects of megalin deletion. This cilastatin-mediated renoprotective effect was dependent on megalin. Cilastatin administration caused selective proteinuria and inhibition of tubular myoglobin uptake similar to that caused by megalin deletion. Conclusions We conclude that megalin plays a critical role in rhabdomyolysis-induced AKI, and megalin interference and inhibition ameliorate rhabdomyolysis-induced AKI. Further investigation of megalin inhibition may inform translational investigation of a novel potential therapy.

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Cannulation of the internal jugular vein (IJV) under ultrasound guidance can reduce complications, such as common carotid artery (CCA) puncture, accidental vertebral artery (VA) puncture. However, these complications still occur, especially in pediatric patients probably due to anatomical predisposition of VA. This study compared differences in anatomical location of VA and IJV between pediatric and adult patients. Children with body weight <20 kg (n = 16) and adults who required central venous or pulmonary arterial pressure monitoring (n = 21) were enrolled. After induction of general anesthesia and tracheal intubation, patients were positioned for IJV cannulation. Images of the right CCA, IJV and VA were recorded by ultrasonography. The size of each vessel, anatomical relationship of other vessels, distance between vessels and between each vessel and skin were measured. The size of VA relative to IJV was significantly larger in children than in adults (14 vs 7 %, P < 0.001). The absolute and relative distance between IJV and VA were significantly shorter in children than those in adults (P < 0.01). The anatomical relationships between IJV and CCA and that between IJV and VA were not different between children and adults. In children, VA was relatively larger and located closer to IJV than adults. The results call for careful attention to the position of VA during ultrasound-guided IJV cannulation especially in children.

Microglia are widely accepted as surveillants in the central nervous system that are continually searching the local environment for signs of injury. Following an inflammatory situation, microglia alter their morphology, extend ramified processes, and undergo cell body hypertrophy. Extracellular nucleotides are recognized as a danger signal by microglia. ADP acting on P2Y12 receptors induce process extension of microglia thereby attracting microglia to the site of adenosine tri-phosphate/ADP leaking or release. However, the question whether ADP/P2Y12 receptor signaling directly stimulates the production or release of inducible factors such as cytokines remains unclear. In this study, we found that CC chemokine ligand 3 (CCL3) is induced by ADP-treated primary microglia. Pharmacological characterization using pertussis toxin, a P2Y12 receptor inhibitor, and a calcium chelator revealed that CCL3 induction was caused by P2Y12 receptor-mediated intracellular calcium elevation. Next, nuclear factor of activated T-cell dephosphorylation and nuclear translocalization were observed. Calcineurin, an inhibitor for nuclear factor of activated T cell, suppressed CCL3 induction. These data indicate that microglial P2Y12 receptors are utilized to trigger an acute inflammatory response in microglia via rapid CCL3 induction after ADP stimulation.

Renal micropuncture and renal 2-photon imaging are seminal techniques in renal physiology. However, micropuncture is limited by dependence on conventional microscopy to surface nephron features, and 2-photon studies are limited in that interventions can only be assessed at the organ, rather than the nephron level. In particular, micropuncture studies of the glomeruli of mice have been challenged by the paucity of surface glomeruli in mice. To address this limitation in order to pursue studies of aspirate from Bowman's space in mouse physiologic models, we developed 2-photon glomerular micropuncture. We present a novel surgical preparation that allows lateral access to the kidney while preserving the required vertical imaging column for 2-photon microscopy. Administration of high molecular weight fluorescein isothiocyanate (FITC)-dextran is used to render the renal vasculature and therefore glomeruli visible for 2-photon imaging. A quantum dot-coated pipette is then introduced under stereotactic guidance to a glomerulus selected from the several to many which may be visualized within the imaging window. In this protocol, we provide details of the preparation, materials, and methods necessary to carry out the procedure. This technique facilitates previously-impossible physiologic study of the kidney, including recovery of filtrate from Bowman's space and all segments of the nephron within the imaging depth limit, about 100 µm below the renal capsule. Pressure, charge and flow may all be measured using the introduced pipette. Here, we provide representative data from liquid chromatography/mass spectrometry performed on aspirate from Bowman's space. We expect this technique to have wide applicability in renal physiologic investigation.