The therapeutic potential of PD-1/PD-L1 pathway on immune-related diseases: Based on the innate and adaptive immune components

Currently, immunotherapy targeting programmed cell death 1 (PD-1) or programmed death ligand 1 (PD-L1) has revolutionized the treatment strategy of human cancer patients. Meanwhile, PD-1/PD-L1 pathway has also been implicated in the pathogenesis of many immune-related diseases, such as autoimmune diseases, chronic infection diseases and adverse pregnancy outcomes, by regulating components of the innate and adaptive immune systems. Given the power of the new therapy, a better understanding of the regulatory effects of PD-1/PD-L1 pathway on innate and adaptive immune responses in immune-related diseases will facilitate the discovery of novel biomarkers and therapeutic drug targets. Targeting this pathway may successfully halt or potentially even reverse these pathological processes. In this review, we discuss recent major advances in PD-1/PD-L1 axis regulating innate and adaptive immune components in immune-related diseases. We reveal that the impact of PD-1/PD-L1 axis on the immune system is complex and manifold and multi-strategies on the targeted PD-1/PD-L1 axis are taken in the treatment of immune-related diseases. Consequently, targeting PD-1/PD-L1 pathway, alone or in combination with other treatments, may represent a novel strategy for future therapeutic intervention on immune-related diseases.

NOD1 activation induces oxidative stress via NOX1/4 in adipocytes

Activation of innate immune components promotes cell autonomous inflammation in adipocytes. Oxidative stress links pattern recognition receptor-mediated detection of inflammatory ligands and the immune response. Reactive oxygen species (ROS) may mediate the effect of nucleotide-binding oligomerization domain protein-1 (NOD1) activation on inflammation in adipocytes. Here, we define the potential role of NADPH oxidase (NOX)-derived ROS in NOD1-mediated inflammatory response in adipocytes. Differentiated 3T3-L1 adipocytes were treated with NOD1 activating ligand D-gamma-Glu-meso-diaminopimelic acid (iE-DAP) to evaluate the oxidative stress and contribution of NOX as source of intracellular ROS. NOD1 activation potently induced ROS generation in 3T3-L1 adipocytes. Of the NOX family members, expression of NOX1 and NOX4 was increased upon NOD1 activation, in a PKCδ-dependent manner. siRNA-mediated down-regulation of NOX1 or NOX4 inhibited NOD1-mediated ROS production and increased the expression of antioxidant defense enzyme catalase and superoxide dismutase (SOD). siRNA-mediated lowering of NOX1 or NOX4 also suppressed NOD1-mediated activation of JNK1/2 and NF-κB, and consequent activation of inflammatory response in 3T3-L1 adipocytes. In summary, our findings demonstrate that NOD1 activation provokes oxidative stress in adipocytes via NOX1/4 and that oxidative stress, at least in part, contributes to induction of inflammatory response. Defining the source of ROS after immune response engagement may lead to new therapeutic strategies for adipose tissue inflammation.