Reorganization of myometrial extracellular matrix (ECM) is essential for the uterus to achieve powerful synchronous contractions during labor. Remodeling of the ECM has been implicated in membrane rupture and cervical ripening. Because maternal obesity is associated with both delivery disorders and elevated circulating leptin levels, this study aimed to assess the ability of leptin to interfere with lipopolysaccharide (LPS)-induced myometrial ECM remodeling. Myometrial biopsy samples were obtained from women undergoing cesarean delivery before labor onset. Myometrial explants were incubated for 48 h with LPS and leptin. LPS challenge was associated with a marked decrease in collagen content and in heat shock protein (HSP) 47 expression, reflecting a disruption in collagen synthesis and an increase in matrix metalloproteinase (MMP) 2 and MMP9 activity and in MMP2, MMP9, and MMP13 expression. Leptin prevented an LPS-induced decrease in myometrial collagen content in a concentration-dependent manner. This effect was associated with an increase in HSP47 expression and a decrease in MMP2 and MMP9 activity and expression. These results show that leptin prevents LPS-induced myometrial remodeling through collagen synthesis stimulation and inhibition of MMP2 and MMP9. Our study strengthens the hypothesis that leptin plays a role in the development of obesity-related delivery disorders.
The beta3 adrenergic receptor (B3-AR) reportedly induces cell proliferation, but the signaling pathways that were proposed, involving either Gs or Gi coupling, remain controversial. To further investigate the role of G protein coupling in B3-AR induced proliferation, we stimulated primary human myometrial smooth muscle cells with SAR150640 (B3-AR agonist) in the absence or presence of variable G-protein inhibitors. Specific B3-AR stimulation led to an Erk1/2 induced proliferation. We observed that the proliferative effects of B3-AR require two Erk1/2 activation peaks (the first after 3min, the second at 8h). Erk1/2 activation at 3min was mimicked by forskolin (adenylyl-cyclase activator), and was resistant to pertussis toxin (Gi inhibitor), suggesting a Gs protein signaling. This first signaling also required the downstream Gs signaling effectors PKA and Src. However, Erk1/2 activation at 8h turned out to be pertussis toxin-dependent, and PKA-independent, indicating a Gi signaling pathway in which Src and PI3K were required. The pharmacological inhibition of both the Gs and Gi pathway abolished B3-AR-induced proliferation. Altogether, these data indicate that B3-AR-induced proliferation depends on the biphasic activation of Erk1/2 sequentially induced by the Gs/PKA/Src and Gi/Src/PI3K signaling pathways.
Hamman's syndrome is the classical association of subcutaneous emphysema and pneumomediastinum, with or without pneumothorax. Its onset during the expulsive phase of childbirth is exceptional. We report here the first case associated with pharyngeal rupture at the level of the piriform sinus and describe the warning signs and the management by endoscopy.
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