Insulin-like Growth Factor 1 Receptor Signaling Is Required for Optimal ATR-CHK1 Kinase Signaling in Ultraviolet B (UVB)-irradiated Human Keratinocytes

UVB wavelengths of light induce the formation of photoproducts in DNA that are potentially mutagenic if not properly removed by the nucleotide excision repair machinery. As an additional mechanism to minimize the risk of mutagenesis, UVB-irradiated cells also activate a checkpoint signaling cascade mediated by the ATM and Rad3-related (ATR) and checkpoint kinase 1 (CHK1) kinases to transiently suppress DNA synthesis and cell cycle progression. Given that keratinocytes in geriatric skin display reduced activation of the insulin-like growth factor 1 receptor (IGF-1R) and alterations in DNA repair rate, apoptosis, and senescence following UVB exposure, here we used cultured human keratinocytes in vitro and skin explants ex vivo to examine how IGF-1R activation status affects ATR-CHK1 kinase signaling and the inhibition of DNA replication following UVB irradiation. We find that disruption of IGF-1R signaling with small-molecule inhibitors or IGF-1 withdrawal partially abrogates both the phosphorylation and activation of CHK1 by ATR and the accompanying inhibition of chromosomal DNA synthesis in UVB-irradiated keratinocytes. A critical protein factor that mediates both ATR-CHK1 signaling and nucleotide excision repair is replication protein A, and we find that its accumulation on UVB-damaged chromatin is partially attenuated in cells with an inactive IGF-1R. These results indicate that mutagenesis and skin carcinogenesis in IGF-1-deficient geriatric skin may be caused by defects in multiple cellular responses to UVB-induced DNA damage, including through a failure to properly suppress DNA synthesis on UVB-damaged DNA templates

Hip Disarticulation in Wound Care: A Case Series

Introduction Hip disarticulation (HD) is a radical lower extremity amputation performed by carefully transecting all muscles and nerves surrounding the hip joint and separating the leg at the joint capsule. This procedure accounts for only 0.5% of all lower extremity amputations in the United States. It is generally performed due to malignant tumors, trauma and limb ischemia. However, it also has a role to play in wound care including management of severe lower extremity infections. It is considered a last resort to be used as a life-preserving measure under emergent circumstances due to high rates of morbidity and mortality. Cases In this case series, we discuss four patients who underwent hip disarticulation specifically for wound care management. The procedure was performed due to various indications including necrotizing fasciitis, gangrene, stump necrosis from previous above the knee amputation and septic arthritis secondary to chronic osteomyelitis. Three of the operations were planned and one was emergent. The procedure was performed successfully in all four patients. Furthermore, all patients were eventually able to be discharged home or to a long term care facility. Conclusion Overall, we conclude that HD should be reserved as a life-saving treatment for various indications including infections or wounds that fail other modalities, limb ischemia, trauma and malignancy. Ideally, this procedure would be planned and done on proper candidates; however, hip disarticulation should still be a consideration in the emergent setting regardless of most optimal patients due to its life saving potential

Enhanced Platelet-activating Factor synthesis facilitates acute and delayed effects of ethanol intoxicated thermal burn injury

Thermal burn injuries in patients alcohol intoxicated result in greater morbidity and mortality. Murine models combining ethanol and localized thermal burn injury reproduce the systemic toxicity seen in human subjects, which consists of both acute systemic cytokine production with multiple organ dysfunction, as well as a delayed systemic immunosuppression. However, the exact mechanisms for these acute and delayed effects are unclear. These studies sought to define the role of the lipid mediator Platelet-activating factor (PAF) in the acute and delayed effects of intoxicated burn injury. Combining ethanol and thermal burn injury resulted in increased enzymatic PAF generation in a keratinocyte cell line in vitro, human skin explants ex vivo, as well as in murine skin in vivo. Further, the acute increase in inflammatory cytokines such as IL-6, and the systemic immunosuppressive effects of intoxicated thermal burn injury, were suppressed in mice lacking PAF receptors. Together, these studies provide a potential mechanism and novel treatment strategies for the augmented toxicity and immunosuppressive effects of thermal burn injury in the setting of acute ethanol exposure, which involves the pleotropic lipid mediator PAF