Faculty Bibliography

Sevoflurane, a commonly used anesthetic, may cause agitation in patients. However, the mechanism underlying this clinical observation remains largely unknown. We thus assessed the effects of sevoflurane on neuronal activation and behaviors in mice. Ten-day-old mice received 2% sevoflurane, 1% isoflurane, or 6% desflurane for 10 minutes. The behavioral activities were recorded and evaluated at one minute after the loss of righting reflex in the mice, which was about two minutes after the anesthetic administration. The neuronal activation was evaluated by c-Fos expression and calcium imaging at one minute after the anesthetic administration. Propofol, which reduces neuronal activation, was used to determine the cause-and-effect of sevoflurane. We found that sevoflurane caused an increase in neuronal activation in primary somatosensory cortex of young mice and behavioral hyperactivity in the mice at one minute after the loss of righting reflex. Desflurane did not induce behavioral hyperactivity and isoflurane only caused behavioral hyperactivity with borderline significance. Finally, propofol attenuated the sevoflurane-induced increase in neuronal activation and behavioral hyperactivity in young mice. These results demonstrate an unexpected sevoflurane-induced increase in neuronal activation and behavioral hyperactivity in young mice. These findings suggest the potential mechanisms underlying the sevoflurane-induced agitation and will promote future studies to further determine whether anesthetics can induce behavioral hyperactivity via increasing neuronal activation.

Dysregulated immunity has been implicated in the pathogenesis of neurodevelopmental disorders but its contribution to synaptic and behavioral deficits in Rett syndrome (RTT) remains unknown. P2X7 receptors (P2X7Rs) are unique purinergic receptors with pro-inflammatory functions. Here, we report in a MECP2-deficient mouse model of RTT that the border of the cerebral cortex exhibits increased number of inflammatory myeloid cells expressing cell-surface P2X7Rs. Total knockout of P2X7Rs in MECP2 deficient mice decreases the number of inflammatory myeloid cells, restores cortical dendritic spine dynamics, and improves the animals' neurological function and social behavior. Furthermore, either genetic depletion of P2X7Rs in bone-marrow derived leukocytes or pharmacological block of P2X7Rs primarily outside of the central nervous system parenchyma, recapitulates the beneficial effects of total P2X7R depletion on the social behavior. Together, our results highlight the pathophysiological roles of P2X7Rs in a mouse model of RTT.

BACKGROUND:transients in neuronal somata, dendrites, and synapses. NEW METHOD/UNASSIGNED:Here we describe five new transgenic mouse lines expressing GCaMP6F (fast) or GCaMP6S (slow) in the central and peripheral nervous system under the control of theThy1.2 promoter. RESULTS:transients in neuronal somata and apical dendrites in the cerebral cortex of both anesthetized and awake behaving mice, as well as in DRG neurons. COMPARISON WITH EXISTING METHOD(S)/UNASSIGNED:These transgenic lines allows calcium imaging of dendrites and somas of pyramidal neurons in specific cortical layers that is difficult to achieve with existing methods. CONCLUSIONS:These GCaMP6 transgenic lines thus provide useful tools for functional analysis of neuronal circuits in both central and peripheral nervous systems.

BACKGROUND: METHODS:on renal inflammation. RESULTS: CONCLUSIONS:Our data support a role for the GSTM1 enzyme in the modulation of oxidative stress, inflammation, and protective metabolites in CKD.

Aging is accompanied by a progressive decrease in learning and memory function. Synaptic loss, one of the hallmarks of normal aging, likely plays an important role in age-related cognitive decline. But little is known about the impact of advanced age on synaptic plasticity and neuronal function in vivo. In this study, we examined the structural dynamics of postsynaptic dendritic spines as well as calcium activity of layer 5 pyramidal neurons in the cerebral cortex of young and old mice. Using transcranial two-photon microscopy, we found that in both sensory and motor cortices, the elimination rates of dendritic spines were comparable between young (3-5 months) and mature adults (8-10 months), but seemed higher in old mice (>20 months), contributing to a reduction of total spine number in the old brain. During the process of motor learning, old mice compared to young mice had fewer new spines formed in the primary motor cortex. Motor training-evoked somatic calcium activity in layer 5 pyramidal neurons of the motor cortex was also lower in old than young mice, which was associated with the decline of motor learning ability during aging. Together, these results demonstrate the effects of aging on learning-dependent synapse remodeling and neuronal activity in the living cortex and suggest that synaptic deficits may contribute to age-related learning impairment.

The dorsal root ganglia (DRG) contain the somas of first-order sensory neurons critical for somatosensation. Due to technical difficulties, DRG neuronal activity in awake behaving animals remains unknown. Here, we develop a method for imaging DRG at cellular and subcellular resolution over weeks in awake mice. The method involves the installation of an intervertebral fusion mount to reduce spinal movement, and the implantation of a vertebral glass window without interfering animals' motor and sensory functions. In vivo two-photon calcium imaging shows that DRG neuronal activity is higher in awake than anesthetized animals. Immediately after plantar formalin injection, DRG neuronal activity increases substantially and this activity upsurge correlates with animals' phasic pain behavior. Repeated imaging of DRG over 5 weeks after formalin injection reveals persistent neuronal hyperactivity associated with ongoing pain. The method described here provides an important means for in vivo studies of DRG functions in sensory perception and disorders.

Activating hair follicle stem cells (HFSCs) to promote hair follicle regrowth holds promise for hair loss therapy, while challenges still remain to develop a scenario that enables enhanced therapeutic efficiency and easy administration. Here we describe a detachable microneedle patch-mediated drug delivery system, mainly made from hair-derived keratin, for sustained delivery of HFSC activators. It was demonstrated that this microneedle device integrated with mesenchymal stem cell (MSC)-derived exosomes and a small molecular drug, UK5099, could enhance the treatment efficiency at a reduced dosage, leading to promoted pigmentation and hair regrowth within 6 days through two rounds of administration in a mouse model. This microneedle-based transdermal drug delivery approach shows augmented efficacy compared to the subcutaneous injection of exosomes and topical administration of UK5099.

Chronic pain is known to induce an amplified aversive reaction to peripheral nociceptive inputs. This enhanced affective response constitutes a key pathologic feature of chronic pain syndromes such as fibromyalgia. However, the neural mechanisms that underlie this important aspect of pain processing remain poorly understood, hindering the development of treatments. Here, we show that a single dose of ketamine can produce a persistent reduction in the aversive response to noxious stimuli in rodent chronic pain models, long after the termination of its anti-nociceptive effects. Furthermore, we demonstrated that this anti-aversive property is mediated by prolonged suppression of the hyperactivity of neurons in the anterior cingulate cortex (ACC), a brain region well known to regulate pain affect. Therefore, our results indicate that it is feasible to dissociate the affective from the sensory component of pain, and demonstrate the potential for low-dose ketamine to be an important therapy for chronic pain syndromes.

Monocytes are a class of leukocytes derived from progenitors in the bone marrow and are prevalent in the blood stream. Although the main function of monocytes is to provide innate immune defenses against infection and injury, their contributions to the central nervous system (CNS) disorders are increasingly recognized. In this review article, we summarize the molecular and physiological properties of monocytes in relation to other myeloid cells. Primarily, we discuss how monocytes (or leukocytes) may affect neuronal function in diseases that are characterized by dysregulated innate immunity and cognitive dysfunction. Under these pathological conditions, monocytes and monocyte-derived cells (1) fail to remove neurotoxic products from CNS, (2) interact with astrocytes at the periphery-brain interfaces to alter synapse development and plasticity, or (3) infiltrate into the CNS to exacerbate neuroinflammation. Through these cellular mechanisms, we speculate that monocytes and other peripheral immune cells may affect brain functioning and contribute to behavioral and cognitive deficits. Better understanding of neuroimmune interactions will help the development of strategies to ameliorate neuronal and cognitive dysfunction associated with dysregulated innate immunity.

Experimental models of peripheral nerve injury have been developed to study mechanisms of neuropathic pain in living animals. The spared nerve injury (SNI) model in rodents is a partial denervation model, in which the common peroneal and tibial nerves are injured, producing consistent and reproducible tactile hypersensitivity in the skin territory of the spared, intact sural nerve. SNI-operated mice require less force applied to the affected limb to elicit a withdrawal behavior as compared to sham mice. This effect is observed as early as 2 days after surgery and lasts for at least 1 month. We describe detailed surgical procedures to establish the SNI mouse model that has been widely used for investigating mechanisms of neuropathic pain.