SOCS3 modulates interleukin-6R signaling preference in dermal fibroblasts

SOCS1 and SOCS3 as key checkpoint molecules in the immune responses associated to skin inflammation and malignant transformation

SOCS are a family of negative inhibitors of the molecular cascades induced by cytokines, growth factors and hormones. At molecular level, SOCS proteins inhibit the kinase activity of specific sets of receptor-associated Janus Activated Kinases (JAKs), thereby suppressing the propagation of intracellular signals. Of the eight known members, SOCS1 and SOCS3 inhibit activity of JAKs mainly induced by cytokines and can play key roles in regulation of inflammatory and immune responses. SOCS1 and SOCS3 are the most well-characterized SOCS members in skin inflammatory diseases, where their inhibitory activity on cytokine activated JAKs and consequent anti-inflammatory action has been widely investigated in epidermal keratinocytes. Structurally, SOCS1 and SOCS3 share the presence of a N-terminal domain containing a kinase inhibitory region (KIR) motif able to act as a pseudo-substrate for JAK and to inhibit its activity. During the last decades, the design and employment of SOCS1 and SOCS3-derived peptides mimicking KIR domains in experimental models of dermatoses definitively established a strong anti-inflammatory and ameliorative impact of JAK inhibition on skin inflammatory responses. Herein, we discuss the importance of the findings collected in the past on SOCS1 and SOCS3 function in the inflammatory responses associated to skin immune-mediated diseases and malignancies, for the development of the JAK inhibitor drugs. Among them, different JAK inhibitors have been introduced in the clinical practice for treatment of atopic dermatitis and psoriasis, and others are being investigated for skin diseases like alopecia areata and vitiligo.

Granulation tissue myofibroblasts during normal and pathological skin healing: The interaction between their secretome and the microenvironment

The first role that was proposed for the myofibroblasts located in skin granulation tissue was to contract the edges of the wound in order to reduce the surface to be repaired. This role, linked to the presence of alpha smooth muscle actin, was very quickly confirmed and is part of the definition of granulation tissue myofibroblasts. However, myofibroblasts are cells that also play a much more central role in wound healing. Indeed, it has been shown that these cells produce large quantities of matrix components, and that they stimulate angiogenesis and can recruit immune cells. These actions take place via the secretion of molecules into their environment or indirectly via the production of microvesicles containing pro-fibrotic and pro-angiogenic molecules. Pathologically, granulation tissue can develop into a hypertrophic scar that histologically looks like granulation tissue, but which can remain for months or even years. It has been hypothesized that the myofibroblasts in these tissues remained present instead of disappearing by apoptosis, causing the maintenance of granulation tissue rather than allowing its change into a mature scar. Understanding the roles of both pathological and healthy myofibroblasts in wound tissue is crucial in order to better intervene in the healing mechanism.

Interleukin 6 Function in the Skin and Isolated Keratinocytes Is Modulated by Hyperglycemia

Diabetes currently affects over twenty-five million Americans. Annual health care cost of diabetes exceeds $254 billion and is associated with a distinct set of diabetic complications that include delayed wound healing and diabetic ulcers. Interleukin 6 (IL-6) plays an important role in wound healing and is known to be elevated in the serum of both type I and type II diabetes patients. This study assesses the expression and function of IL-6 in the hyperglycemic epidermis and keratinocyte culture. Streptozotocin-treated mice were wounded six weeks after induction of hyperglycemia. Wound closure, protein, and mRNA expression were assessed up to 13 days of postwounding. Wound closure was delayed 4-5 days in hyperglycemic animals. Hyperglycemic wounds displayed greater IL-6 and IL-6Rα protein expression at 1, 7, and 10 days of postwounding compared to euglycemic control. However, IL-6Rα mRNA expression was reduced at all time points beyond day 1, while IL-6 mRNA expression did not significantly differ at any time point. SOCS3 mRNA expression was higher in the hyperglycemic skin at every time point. Imaging of fluorescent immunohistology also revealed significantly lower expression of SOCS3, but higher nuclear pSTAT3 in the epidermis of the hyperglycemic skin. Primary mouse keratinocytes cultured in high glucose for 7 days displayed 2-fold higher IL-6Rα mRNA and higher rmIL-6-induced nuclear pSTAT3, but lower SOCS3 basal levels compared to normal glucose-cultured cells. Thus, it appears that delayed diabetic skin wound healing is associated with increased induction and expression of IL-6 and its receptor, but its function in epidermal keratinocytes may be impaired.

AG311, a small molecule inhibitor of complex I and hypoxia-induced HIF-1α stabilization

Cancer cells have a unique metabolic profile and mitochondria have been shown to play an important role in chemoresistance, tumor progression and metastases. This unique profile can be exploited by mitochondrial-targeted anticancer therapies. A small anticancer molecule, AG311, was previously shown to possess anticancer and antimetastatic activity in two cancer mouse models and to induce mitochondrial depolarization. This study defines the molecular effects of AG311 on the mitochondria to elucidate its observed efficacy. AG311 was found to competitively inhibit complex I activity at the ubiquinone-binding site. Complex I as a target for AG311 was further established by measuring oxygen consumption rate in tumor tissue isolated from AG311-treated mice. Cotreatment of cells and animals with AG311 and dichloroacetate, a pyruvate dehydrogenase kinase inhibitor that increases oxidative metabolism, resulted in synergistic cell kill and reduced tumor growth. The inhibition of mitochondrial oxygen consumption by AG311 was found to reduce HIF-1α stabilization by increasing oxygen tension in hypoxic conditions. Taken together, these results suggest that AG311 at least partially mediates its antitumor effect through inhibition of complex I, which could be exploited in its use as an anticancer agent.

SOCS3 expression correlates with severity of inflammation, expression of proinflammatory cytokines, and activation of STAT3 and p38 MAPK in LPS-induced inflammation in vivo

SOCS3 is an inducible endogenous negative regulator of JAK/STAT pathway, which is relevant in inflammatory conditions. We used a model of LPS-induced periodontal disease in rats to correlate SOCS3 expression with the inflammatory status. In vitro we used a murine macrophage cell line to assess the physical interaction between SOCS3 and STAT3 by coimmunoprecipitation. 30 ug of LPS from Escherichia coli were injected in the gingival tissues on the palatal aspect of first molars of the animals 3x/week for up to 4 weeks. Control animals were injected with the vehicle (PBS). The rats were sacrificed at 7, 15, and 30 days. Inflammation and gene expression were assessed by stereometric analysis, immunohistochemistry, RT-qPCR, and western blot. LPS injections increased inflammation, paralleled by an upregulation of SOCS3, of the proinflammatory cytokines IL-1 β , IL-6, and TNF- α and increased phosphorylation of STAT3 and p38 MAPK. SOCS3 expression accompanied the severity of inflammation and the expression of proinflammatory cytokines, as well as the activation status of STAT3 and p38 MAPK. LPS stimulation in a macrophage cell line in vitro induced transient STAT3 activation, which was inversely correlated with a dynamic physical interaction with SOCS3, suggesting that this may be a mechanism for SOCS3 regulatory function.