Glutathione is an abundant natural tripeptide found within almost all cells. Glutathione is highly reactive and is often found conjugated to other molecules via its sulfhydryl moiety. It instils several vital roles within a cell including antioxidation, maintenance of the redox state, modulation of the immune response and detoxification of xenobiotics. With respect to cancer, glutathione metabolism is able to play both protective and pathogenic roles. It is crucial in the removal and detoxification of carcinogens, and alterations in this pathway, can have a profound effect on cell survival. However, by conferring resistance to a number of chemotherapeutic drugs, elevated levels of glutathione in tumour cells are able to protect such cells in bone marrow, breast, colon, larynx and lung cancers. Here we present a number of studies investigating the role of glutathione in promoting cancer, impeding chemotherapy, and the use of glutathione modulation to enhance anti-neoplastic therapy.

The decline of cognitive function has emerged as one of the greatest health threats of old age. Age-related cognitive decline is caused by an impacted neuronal circuitry, yet the molecular mechanisms responsible are unknown. C1q, the initiating protein of the classical complement cascade and powerful effector of the peripheral immune response, mediates synapse elimination in the developing CNS. Here we show that C1q protein levels dramatically increase in the normal aging mouse and human brain, by as much as 300-fold. This increase was predominantly localized in close proximity to synapses and occurred earliest and most dramatically in certain regions of the brain, including some but not all regions known to be selectively vulnerable in neurodegenerative diseases, i.e., the hippocampus, substantia nigra, and piriform cortex. C1q-deficient mice exhibited enhanced synaptic plasticity in the adult and reorganization of the circuitry in the aging hippocampal dentate gyrus. Moreover, aged C1q-deficient mice exhibited significantly less cognitive and memory decline in certain hippocampus-dependent behavior tests compared with their wild-type littermates. Unlike in the developing CNS, the complement cascade effector C3 was only present at very low levels in the adult and aging brain. In addition, the aging-dependent effect of C1q on the hippocampal circuitry was independent of C3 and unaccompanied by detectable synapse loss, providing evidence for a novel, complement-and synapse elimination-independent role for C1q in CNS aging.

Deficiency in C1q, the recognition component of the classical complement cascade and a pattern recognition receptor involved in apoptotic cell clearance, leads to lupus-like auto-immune diseases characterized by auto-antibodies to self proteins and aberrant innate immune cell activation likely due to impaired clearance of apoptotic cells. Here, we developed an autologous system using primary human lymphocytes and monocyte-derived macrophages (HMDMs) to characterize the effect of C1q on macrophage gene expression profiles during the uptake of apoptotic cells. C1q bound to autologous apoptotic lymphocytes modulated expression of genes associated with JAK/STAT signaling, chemotaxis, immunoregulation and NLRP3 inflammasome activation in LPS-stimulated HMDMs. Specifically, C1q sequentially induced type I interferons (IFNs), IL-27 and IL-10 in LPS-stimulated HMDMs and IL-27 in HMDMs when incubated with AL conditioned media. Co-incubation with C1q tails prevented the induction of type I IFNs and IL-27 in a dose dependent manner and neutralization of type I IFNs partially prevented IL-27 induction by C1q. Finally, C1q decreased procaspase-1 cleavage and caspase-1 dependent cleavage of IL-1β suggesting potent inhibitory effect of C1q on inflammasome activation. These results identify specific molecular pathways induced by C1q to suppress macrophage inflammation providing potential therapeutic targets to control macrophage polarization, and thus inflammation and autoimmunity.

Complement is a critical system of enzymes, regulatory proteins, and receptors that regulates both innate and adaptive immune responses. Natural mutations in complement molecules highlight their requirement in regulation of a variety of human conditions including infectious disease and autoimmunity. As sentinels of the immune system, macrophages are specialized to respond to infectious microbes, as well as normal and altered self, and dictate appropriate immune responses. Complement components such as anaphylatoxins (C3a and C5a) and opsonins [C3b, C1q, mannan binding lectin (MBL)] influence macrophage responses. While anaphylatoxins C3a and C5a trigger inflammasome activation, opsonins such as C1q and related molecules (MBL and adiponectin) downregulate inflammasome activation and inflammation, and upregulate engulfment of apoptotic cells consistent with a pro-resolving or M2 macrophage phenotype. This review summarizes our current understanding of the influence of the complement system on macrophage polarization with an emphasis on C1q and related molecules.

C1q, the first component of the classical complement pathway, is also a pattern recognition receptor involved in the recognition and clearance of apoptotic cells. C1q deficiency in humans leads to development of lupus-like autoimmune disease, and it has been speculated that impaired clearance of apoptotic cells may contribute to disease development. Since phagocytes initiate specific and appropriate immune responses as a result of initial ligand-receptor interactions, regulation of gene expression by C1q may also contribute to the sculpting of an immune response to the ingested “self-Ags.” In this study, the role of C1q in apoptotic cell clearance and subsequent modulation of cytokine release by phagocytes was assessed including donor matched human monocytes, monocyte-derived macrophages (HMDMs), and dendritic cells (DCs). First, C1q binding is much greater to late compared with early apoptotic cells. Second, C1q binding to apoptotic cells significantly enhanced the levels of ingestion by monocytes but had no effect on HMDM and DC uptake. Third, in the presence of serum, C1q bound to apoptotic cells, activated the complement pathway, leading to C3b deposition, and enhancement of uptake of apoptotic cells by monocytes, HMDMs, and DCs. Finally, although C1q, either immobilized on a plate or bound to apoptotic cells, modulates the LPS-induced cytokine levels released by human monocytes, HMDMs, and DCs toward a more limited immune response, both the degree and direction of modulation differed significantly depending on the differentiation state of the phagocyte, providing further evidence of the integration of these cell- and environment-specific signals in determining appropriate immune responses.