Role of ROCK expression in gallbladder smooth muscle contraction

Actin Dynamics, Regulated by RhoA-LIMK-Cofilin Signaling, Mediates Rod Photoreceptor Axonal Retraction After Retinal Injury

Purpose

Retraction of the axon terminals of rod photoreceptors after retinal detachment breaks the first synapse in the visual pathway, resulting in visual impairment. Previous work showed that the mechanism of axonal retraction involves RhoA signaling and its downstream effector LIM Kinase (LIMK) activation. We examined the response of the downstream component cofilin, a direct binding protein of actin filaments, as well as the regulation by RhoA-LIMK-Cofilin signaling of actin assembly/disassembly, in the presynaptic ribbon terminal of injured rod cells.

Methods

Injury was produced by retinal detachment or rod cell isolation. Detached porcine retina was probed for levels and localization of phosphorylated cofilin with Western blots and confocal microscopy, whereas rod cell cultures of dissociated salamander retina were examined for filamentous actin assembly/disassembly with a barbed end assay and phalloidin staining.

Results

A detachment increased phosphorylation of cofilin in retinal explants; phosphorylation occurred in rod terminals in sections of detached retina. Isolation of rod cells resulted in axon retraction accompanied by an increase in actin barbed ends and a decrease in net filament labeling. All changes were significantly reduced by either Rho kinase (ROCK) or LIMK inhibition, using Y27632 or BMS-5, respectively. Cytochalasin D also reduced retraction and stabilized filaments in isolated rod cells.

Conclusions

These results indicate that actin depolymerization via activation of RhoA downstream kinases and cofilin contributes to axon retraction. Preventing depolymerization, in addition to actomyosin contraction, may stabilize ribbon synapses after trauma.

Relationship between folded gallbladder and risk of gallstone formation

AIM: To explore the relationship between morphologically folded gallbladder and gallstone formation.

METHODS: A case-control study was performed in 169 patients with cholecystolithiasis who underwent laparoscopic cholecystectomy (stone group) and 200 healthy persons without cholecystolithiasis who underwent physical examination (control group) from January 2013 to December 2014 in the Department of Hepatobiliary Surgery, the Affiliated Dalian Friendship Hospital, Dalian Medical University. Criteria for the diagnosis of folded gallbladder included: (1) ultrasonography showed separation of the gallbladder in the control group, while CT and laparoscopic examinations showed that the angle between the long axis of the gallbladder and the folded part was ≥ 60° in the observation group; and (2) adenomyoma of the gallbladder was excluded pathologically. According to the proportion of the cube of the affected gallbladder, the morphologic folding was classified as 1/4, 1/3, 1/2, and 2/3. The type of cholecystolithiasis was also classified.

RESULTS: There were 54 (32%) cases of folded gallbladder in the stone group and 14 (7%) cases in the control group, and there was a significant difference between the two groups. There were 6 cases with 1/4 folding, 18 cases with 1/3, 13 cases with 1/2, and 17 cases with 2/3. There were 52 cases of folding towards the right and 2 cases of folding towards the left. According to the type of cholecystolithiasis, there were 32 (n = 54, 59.3%) cases of bile pigment calculus in the folded gallbladder group and 46 (n = 115, 40%) cases in the non-folded group (P < 0.05).

CONCLUSION: Folded gallbladder has a high incidence rate in patients with gallstones and is one of major risk factors for gallstone formation. The rate of bile pigment calculu is high in patients with folded gallbladder.