Periglomerular afferent innervation of the mouse renal cortex

Recent studies using a novel method for targeted ablation of afferent renal nerves have demonstrated their importance in the development and maintenance of some animal models of hypertension. However, relatively little is known about the anatomy of renal afferent nerves distal to the renal pelvis. Here, we investigated the anatomical relationship between renal glomeruli and afferent axons identified based on transient receptor potential vanilloid 1 channel (TRPV1) lineage or calcitonin gene related peptide (CGRP) immunolabeling. Analysis of over 6,000 (10,000 was accurate prior to the removal of the TH data during the review process) glomeruli from wildtype C57BL/6J mice and transgenic mice expressing tdTomato in TRPV1 lineage cells indicated that approximately half of all glomeruli sampled were closely apposed to tdTomato+ or CGRP+ afferent axons. Glomeruli were categorized as superficial, midcortical, or juxtamedullary based on their depth within the cortex. Juxtamedullary glomeruli were more likely to be closely apposed by afferent axon subtypes than more superficial glomeruli. High-resolution imaging of thick, cleared renal slices and subsequent distance transformations revealed that CGRP+ axons closely apposed to glomeruli were often found within 2 microns of nephrin+ labeling of glomerular podocytes. Furthermore, imaging of thick slices suggested that CGRP+ axon bundles can closely appose multiple glomeruli that share the same interlobular artery. Based on their expression of CGRP or tdTomato, prevalence near glomeruli, proximity to glomerular structures, and close apposition to multiple glomeruli within a module, we hypothesize that periglomerular afferent axons may function as mechanoreceptors monitoring glomerular pressure. These anatomical findings highlight the importance of further studies investigating the physiological role of periglomerular afferent axons in neural control of renal function in health and disease.

Reevaluating tear gas toxicity and safety

Tear gases, or chemical demonstration control agents (DCA), were originally created as weapons that could severely disable or kill enemy troops. Though banned in war, these chemicals are still used in domestic policing. Here we review the available scientific literature on tear gas, summarizing findings from animal and environmental studies as well describing data from new human studies. We find a lack of scientific evidence supporting the safety of tear gas, especially regarding its long-term impacts on human health and the environment. Many of the available studies were published decades ago, and do not parse data by variables such as chemical type and exposure time, nor do they account for the diversity of individuals who are exposed to tear gas in real-life situations. Due to the dearth of scientific research and the misinterpretation of some of the available studies, we conclude that a serious reevaluation of chemical DCA safety and more comprehensive exposure follow-up studies are necessary.

Function of Renal Nerves in Kidney Physiology and Pathophysiology

Renal sympathetic (efferent) nerves play an important role in the regulation of renal function, including glomerular filtration, sodium reabsorption, and renin release. The kidney is also innervated by sensory (afferent) nerves that relay information to the brain to modulate sympathetic outflow. Hypertension and other cardiometabolic diseases are linked to overactivity of renal sympathetic and sensory nerves, but our mechanistic understanding of these relationships is limited. Clinical trials of catheter-based renal nerve ablation to treat hypertension have yielded promising results. Therefore, a greater understanding of how renal nerves control the kidney under physiological and pathophysiological conditions is needed. In this review, we provide an overview of the current knowledge of the anatomy of efferent and afferent renal nerves and their functions in normal and pathophysiological conditions. We also suggest further avenues of research for development of novel therapies targeting the renal nerves.

Generation and validation of a conditional knockout mouse model for desmosterolosis

The enzyme 3β-hydroxysterol-Δ24 reductase (DHCR24, EC 1.3.1.72) catalyzes the conversion of desmosterol to cholesterol and is obligatory for post-squalene cholesterol synthesis. Genetic loss of this enzyme results in desmosterolosis (MIM #602398), a rare disease that presents with multiple congenital anomalies, features of which overlap with subjects with the Smith-Lemli-Opitz syndrome (another post-squalene cholesterol disorder). Global knockout (KO) of Dhcr24 in mice recapitulates the biochemical phenotype, but pups die within 24 h from a lethal dermopathy, limiting its utility as a disease model. Here, we report a conditional KO mouse model (Dhcr24^flx/flx) and validate it by generating a liver-specific KO (Dhcr24^{flx/flx,Alb-Cre}). Dhcr24^{flx/flx,Alb-Cre} mice showed normal growth and fertility, while accumulating significantly elevated levels of desmosterol in plasma and liver. Of interest, despite the loss of cholesterol synthesis in the liver, hepatic architecture, gene expression of sterol synthesis genes, and lipoprotein secretion appeared unchanged. The increased desmosterol content in bile and stool indicated a possible compensatory role of hepatobiliary secretion in maintaining sterol homeostasis. This mouse model should now allow for the study of the effects of postnatal loss of DHCR24, as well as role of tissue-specific loss of this enzyme during development and adulthood.

Transcranial focused ultrasound neuromodulation of the human primary motor cortex

Transcranial focused ultrasound is an emerging form of non-invasive neuromodulation that uses acoustic energy to affect neuronal excitability. The effect of ultrasound on human motor cortical excitability and behavior is currently unknown. We apply ultrasound to the primary motor cortex in humans using a novel simultaneous transcranial ultrasound and magnetic stimulation paradigm that allows for concurrent and concentric ultrasound stimulation with transcranial magnetic stimulation (TMS). This allows for non-invasive inspection of the effect of ultrasound on motor neuronal excitability using the motor evoked potential (MEP). We test the effect of ultrasound on single pulse MEP recruitment curves and paired pulse protocols including short interval intracortical inhibition (SICI) and intracortical facilitation (ICF). In addition, we test the effect of ultrasound to motor cortex on a stimulus response reaction time task. Results show ultrasound inhibits the amplitude of single-pulse MEPs and attenuates intracortical facilitation but does not affect intracortical inhibition. Ultrasound also reduces reaction time on a simple stimulus response task. This is the first report of the effect of ultrasound on human motor cortical excitability and motor behavior and confirms previous results in the somatosensory cortex that ultrasound results in effective neuronal inhibition that confers a performance advantage.

Abstract 229: Development of a Conditional Knockout of Cholesterol Synthesis in the Mouse

Dhcr24 (3β-hydroxysteroid-Δ24 reductase) is responsible for reducing the C24-C25 double bond in sterol intermediates of cholesterol and this step is necessary to synthesize cholesterol. In humans, mutations in the Dhcr24 gene cause desmosterolosis (OMIM #602398), characterized by severe developmental abnormalities and elevated levels of desmosterol in plasma and tissue. The first case was reported in 1998 when a premature infant died shortly after birth, had elevated levels of desmosterol and phenotypic abnormalities. Although initially reported as a ‘cholesterol-free mouse’ in Science, the global Dhcr24 knockout mouse shows neonatal lethality within 10h of birth, a finding reproduced in many different laboratories, despite sharing the original knockout mouse.

We now report a conditional knockout model using the LoxP-cre deletion system and show proof-of-principle by studying effects Dhcr24 deletion in the liver.