Toll-like receptor 7 contributes to neuropathic pain by activating NF-κB in primary sensory neurons.

Toll like receptor 7 (TLR7) is expressed in neurons of the dorsal root ganglion (DRG), but whether it contributes to neuropathic pain is elusive. We found that peripheral nerve injury caused by ligation of the fourth lumbar (L4) spinal nerve (SNL) or chronic constriction injury of sciatic nerve led to a significant increase in the expression of TLR7 at mRNA and protein levels in mouse injured DRG. Blocking this increase through microinjection of the adeno-associated virus (AAV) 5 expressing TLR7 shRNA into the ipsilateral L4 DRG alleviated the SNL-induced mechanical, thermal and cold pain hypersensitivities in both male and female mice. This microinjection also attenuated the SNL-induced increases in the levels of phosphorylated extracellular signal-regulated kinase ½ (p-ERK1/2) and glial fibrillary acidic protein (GFAP) in L4 dorsal horn on the ipsilateral side during both development and maintenance periods. Conversely, mimicking this increase through microinjection of AAV5 expressing full-length TLR7 into unilateral L3/4 DRGs led to elevations in the amounts of p-ERK1/2 and GFAP in the dorsal horn, augmented responses to mechanical, thermal and cold stimuli, and induced the spontaneous pain on the ipsilateral side in the absence of SNL. Mechanistically, the increased TLR7 activated the NF-κB signaling pathway through promoting the translocation of p65 into the nucleus and phosphorylation of p65 in the nucleus from the injured DRG neurons. Our findings suggest that DRG TLR7 contributes to neuropathic pain by activating NF-κB in primary sensory neurons. TLR7 may be a potential target for therapeutic treatment of this disorder.

Injectable PLGA-Coated Ropivacaine Produces A Long-Lasting Analgesic Effect on Incisional Pain and Neuropathic Pain.

The management of persistent postsurgical pain and neuropathic pain remains a challenge in the clinic. Local anesthetics have been widely used as simple and effective treatment for these 2 disorders, but the duration of their analgesic effect is short. We here reported a new poly lactic-co-glycolic acid (PLGA)-coated ropivacaine that was continuously released in vitro for at least 6 days. Perisciatic nerve injection of the PLGA-coated ropivacaine attenuated paw incision-induced mechanical allodynia and heat hyperalgesia during the incisional pain period, and spared nerve injury-induced mechanical and cold allodynia for at least 7 days postinjection. This effect was dose-dependent. Perisciatic nerve injection of the PLGA-coated ropivacaine did not produce detectable inflammation, tissue irritation, or damage in the sciatic nerve and surrounding muscles at the injected site, dorsal root ganglion, spinal cord, or brain cortex, although the scores for grasping reflex were mildly and transiently reduced in the higher dosage-treated groups. PERSPECTIVE: Given that PLGA is an FDA-approved medical material, and that ropivacaine is used currently in clinical practice, the injectable PLGA-coated ropivacaine represents a new and highly promising avenue in the management of postsurgical pain and neuropathic pain.

Long noncoding RNA H19 in the injured dorsal root ganglion contributes to peripheral nerve injury-induced pain hypersensitivity.

Peripheral nerve injury-induced changes in gene transcription and translation in the dorsal root ganglion (DRG) play a critical role in the development and maintenance of neuropathic pain. Long noncoding RNAs (lncRNAs) regulate gene expression. Here, we report that peripheral nerve injury caused by ligation of the fourth spinal nerve (SNL) led to a time-dependent increase in the expression in H19, an lncRNA, in the injured DRG. Microinjection of a specific H19 siRNA, but not negative control scrambled siRNA, into the injured DRG 4 days before SNL alleviated mechanical allodynia and thermal hyperalgesia on days 3 and 5 post-SNL. Additionally, DRG microinjection of the H19 siRNA on day 7 after SNL reduced mechanical allodynia and thermal hyperalgesia on days 10 and 12 post-SNL. DRG microinjection of neither siRNA affected locomotor activity and acute basal responses to mechanical and thermal stimuli. Our findings suggest that H19 participates in the peripheral mechanism underlying the development and maintenance of neuropathic pain. H19 may be a potential target for treatment of this disorder.

Symptomatic Infratentorial Thrombosed Developmental Venous Anomaly: Case Report and Review of the Literature.

BACKGROUND: Developmental venous anomalies (DVAs) are variations of normal transmedullary veins draining white and gray matter. In the vast majority of cases, DVAs are diagnosed incidentally and should be considered as benign entities. In extremely rare circumstances, DVAs may become symptomatic due to mechanical or flow-related etiologies. Thrombosis of the collector vein of a DVA is a rare type of a flow-related complication with only 29 cases reported in the literature, the majority of which are supratentorial. Infratentorial thrombosed DVAs are thus extremely rare and the few cases reported have typically caused symptoms due to venous ischemic infarctions. SUMMARY: We report a case of an infratentorial DVA with a thrombosed drainage vein in a patient with nonhemorrhagic, noninfarcted venous congestive edema, which was successfully treated with high-dose glucocorticoids and short-term anticoagulation. We review the pertinent venous anatomy of the posterior fossa as well as the literature of symptomatic infratentorial thrombosed DVAs. KEY MESSAGE: The presented case of an infratentorial thrombosed DVA with cerebellar and pontine venous congestive edema is extremely rare. A working knowledge of posterior fossa venous anatomy and possible pathomechanisms responsible for the rarely symptomatic lesion will aid in the timely and efficacious treatment of such lesions.