Porphyromonas gingivalis mediated periodontal disease and atherosclerosis: disparate diseases with commonalities in pathogenesis through TLRs

Toll-like receptors (TLRs) are a group of pathogen-associated molecular pattern receptors, which play an important role in innate immune signaling in response to microbial infection. It has been demonstrated that TLRs are differentially up regulated in response to microbial infection and chronic inflammatory diseases such as atherosclerosis. Furthermore hyperlipidemic mice deficient in TLR2, TLR4, and MyD88 signaling exhibit diminished inflammatory responses and decreased atherosclerosis. Accumulating evidence has implicated specific infectious agents including the periodontal disease pathogen Porphyromonas gingivalis in the progression of atherosclerosis. Evidence in humans suggesting that periodontal infection predisposes to atherosclerosis is derived from studies demonstrating that the periodontal pathogen P. gingivalis resides in the wall of atherosclerotic vessels and seroepidemiological studies demonstrating an association between pathogen-specific IgG antibodies and atherosclerosis. We have established that the inflammatory signaling pathways that P. gingivalis utilizes is dependent on the cell type and this specificity clearly influences innate immune signaling in the context of local and distant chronic inflammation induced by this pathogen. We have demonstrated that P. gingivalis requires TLR2 to induce oral inflammatory bone lose in mice. Furthermore, we have demonstrated that P. gingivalis infection accelerates atherosclerosis in hyperlipidemic mice with an associated increase in expression of TLR2 and TLR4 in atherosclerotic lesions. Our recent work with P. gingivalis has demonstrated the effectiveness of specific intervention strategies (immunization) in the prevention of pathogen-accelerated atherosclerosis. Improved understanding of the mechanisms driving infection, and chronic inflammation during atherosclerosis may ultimately provide new targets for therapy.     

Hormone mediation of immune responses in the progression of diabetes,rheumatoid arthritis and periodontal diseases

The crucial role of the immune response is common to diabetes mellitus (DM), rheumatoid arthritis (RA) and periodontal disease. This review identifies advances in this field and exciting paradigms in their management. Uncontrolled hyperglycaemia in diabetic patients results in the formation of advanced glycation end products (AGEs), which are detrimental to cell structure and function. Altered host resistance such as defective migration of PMN, impaired phagocytosis and an exaggerated inflammatory response to microbial products also compromises healing in uncontrolled diabetic patients, further compromised in smokers. Nicotine has well documented effects on the immune response, cell adhesion proteins and apoptosis which affect the severity of disease presentation and response to treatment. Rheumatoid arthritis is a multifactorial disease that results in severe destruction of synovial cartilage and bone. Local secretion of large amounts of TNF-alpha and IL-1 due to activation of immunocompetent cells characterises the pathophysiology of RA. This has lead to the emergence of TNF-alpha inhibitors such as etanercept and infliximab in its management. Periodontal disease has a microbial aetiology. But it is similar to RA, in its cyclical pattern of destruction associated with high levels of pro-inflammatory cytokines, which can persist after removal of the antigenic stimulus. Non steroidal anti-inflammatory agents (NSAIDs) have been used as an adjunct to mechanical removal of bacterial antigen, in the management of periodontal disease. The non-reproductive functions of steroid hormones include effects on immunocompetent cells, fibroblasts and osteoblasts, which affect the initiation and progression of inflammatory diseases. Hormone replacement therapy could be another facet in a multifaceted treatment approach in these patients, where indicated.     

Molecules of infectious agents as immunomodulatory drugs

Microbes produce a wide range of molecules that can modulate eukaryotic immune responses. These include factors that subvert protective mechanisms in order to facilitate pathogen colonization and persistence. Viral, bacterial and parasite-derived molecules have been identified that can inhibit inflammatory responses. However, in addition to the plethora of microbial factors that suppress immune responses, the most potent immune activators are also of microbial origin. These include the bacterial enterotoxins, parasite-derived excretory-secretory products and viral nucleic acids. In fact, there are examples of immune modulators that can exert either stimulatory or suppressive effects depending on the mode of delivery, dose and experimental model. There is presently great interest in the therapeutic exploitation of these factors, for example as a means to stimulate enhanced immune responses to a new generation of subunit vaccines or to inhibit deleterious immune mediated diseases. This short review, describes representative microbial immunomodulators, their modes of action and the potential for therapeutic application.     

铜绿假单胞菌的群体感应系统及其抑制剂研究进展

群体感应系统(quorum sensing system, QS)是一种微生物细胞与细胞间的交流系统。铜绿假单胞菌是该系统的典型代表,可调控细菌产生对抗生素的耐药、形成生物膜、产生毒力因子,并且减弱宿主的免疫应答。群体感应系统抑制剂(quorum sensing inhibitors, QSIs)在不影响细菌生长的前提下可降低细菌的毒性,且增强细菌生物膜对抗生素治疗的敏感性,这些特点使QSIs成为目前抗感染领域的研发热点。本文就铜绿假单胞菌的群体感应系统及QSIs的研究进展进行了综述。     

活性氧在牙周炎中病理作用的研究进展

牙周炎是一种常见的慢性炎症疾病,引起牙周组织的损伤,受损部位包括牙龈、牙周韧带和牙槽骨。引发牙周炎的主要原因是人体对口腔微生物及其代谢产物的免疫反应,其中活性氧(ROS)的稳态失衡和抗氧化防御系统在牙周炎的发病进程中扮演了重要的促进角色。升高的ROS引发病灶组织细胞的自噬,导致相应的组织细胞凋亡,进一步阐明牙周炎自噬过程中氧还原调控的作用和机制,对牙周病治疗策略的研究具有一定的临床指导意义。笔者对ROS在牙周炎中的相关病理作用做了简要综述。     

Microbes and their products--physiological effects upon mammalian mucosa

A dynamic array of interactions occurs between pathogens and host mucosal surfaces. The signature molecules unique to microbial pathogens allow the mammalian immune system to recognize them as non-self. This recognition, mediated by the toll-like receptor proteins, results in innate immune responses targeted against the invading organism. Pathogens also elaborate a variety of proteins that actively engage host signaling pathways and subvert them to facilitate their growth and dispersal. These interactions, developed over a long evolutionary period, have been specialized to exquisite detail. These proteins and toxins are either secreted into the medium or directly delivered into host cells by specialized secretion systems. An array of host function alterations is mediated by microbial pathogens including inflammatory responses, secretory responses, alteration of host cytoskeleton, disruption of epithelial tight junctions and apoptosis. The signaling axes involved in these interactions are potential targets for therapeutic strategies against infectious microbes.     

Oral inflammatory process and general health. Part 1: The focal infection and the oral inflammatory lesion

A focal infection is a localized or generalized infection caused by the dissemination of microorganisms or toxic products from a focus of infection in various organic districts, including the oral district. In the Part 1 of this two-part review article, after historical signs, the Authors describe the current pathogenic concepts like the "immuno-allergic theory" and the formation of auto-antibodies in human body, contributing to the genesis of autoimmune illnesses sustained by individual reactivity linked to eredo-constitutionality. Some theories suppose a focal origin even for general pathology such as cancer, sarcoidosis, multiple sclerosis, amyotrophic lateral sclerosis, autism, Guillain-Barré syndrome, Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal infections (PANDAS), Tourette's syndrome, myasthenia gravis, polycystic kidney disease, obesity, Alzheimer's disease and diabetes mellitus. Laboratory analyses (leucocytic formula, protein electrophoresis, C-reactive protein, REUMA test VES, TAS, etc.) are suggestive of the presence of an inflammatory process or of the presence of an aspecific answer to an inflammatory situation. The DNA-Polymerase Chain Reaction method (PCR) is fundamental for the diagnosis of bacterial and viral infections, particularly for those that have non-culturable microorganisms or in cases where are present but in extremely small number in the sample to be analyzed. A positive result confirms the diagnosis, but negative result is not indicator of the absence of illness. Even for oral inflammatory lesions, different basic mechanisms concerning the possible association with systemic diseases exist. They concern local spread, metastatic spread or immunologic cross-reactivity. In this case we assume that most of the ailments come from dental or periodontal foci, as in the bacterial endocarditis, but instead of considering them as possible pathogenetic mechanism of an immune nature, we consider them as originated by the body's response to the presence of bacterial antigens through the formation of specific antibodies. Much researche, sometimes contrasting, has evaluated periodontal pathogens in atheromatous plaques isolated from patients with chronic periodontitis. Oral inflammatory lesions have been shown unequivocally to contribute to elevated systemic inflammatory responses. In some researches intensive periodontal therapy showed a significant reduction of lymphocyte formula, of CRP levels, of interleukin-6 (IL-6) and of LDL cholesterol after two months.     

Inflammatory mechanisms and redox status in periodontal and cardiometabolic diseases: effects of adjunctive nutritional antioxidants and statins

Periodontal pathogens in plaque biofilm initiate periodontitis, which is influenced by genetic and environmental factors. The resultant pro-oxidant status imposed on the periodontium, exacerbated by episodic hyperinflammatory damage contributes to progression of periodontitis and tooth loss in susceptible subjects. Increasing documentation of bi-directional connections between periodontal and cardiometabolic disorders makes it an intriguing area of therapeutic intervention for mutual benefit. Periodontitis and associated comorbidities demonstrate similar risk markers of inflammation during disease progression. Depending on the extent and severity of the inflammatory response, periodontitis could impact significantly on systemic inflammatory loading and influence the progression of endothelial dysfunction, atherosclerotic plaque instability, dyslipidaemia and insulin resistance. Some of the common mechanisms involved are discussed, relevant to periodontal and cardiometabolic disorders which have been documented as having a bidirectional relationship with periodontal disease progression; abating in response to treatment. Periodontal disease may be a useful marker of a susceptible immune system, or directly affect the progression of systemic diseases due to inflammatory loading. These mechanisms mediated by coordinated actions of cytokines, acute phase proteins, enzymes and their sequelae are addressed in the context of conventional periodontal therapy and its outcome with a modulatory role on metabolic diseases. Applications for the role of nutritional and therapeutic antioxidants as adjuncts in diseases with a distinctly prooxidant profile are discussed. Accurate therapeutic targeting as an adjunct to conventional periodontal treatment in this context, for mutual benefit to subjects with periodontitis and cardiometabolic diseases is a challenge.     

Use of cytokines in infection

Infectious disease remains an ever-growing health concern worldwide due to increasing antibiotic-resistant microbial strains, immune-compromised populations, international traffic and globalisation, and bioterrorism. There exists an urgent need to develop novel prophylactic and therapeutic strategies. In addition to classic antibiotic therapeutics, immune-modulatory molecules such as cytokines or their inhibitors represent a promising form of antimicrobial therapeutics or immune adjuvant used for the purpose of vaccination. These molecules, in the form of either recombinant protein or transgene, exert their antimicrobial effect by enhancing infectious agent-specific immune activation or memory development, or by dampening undesired inflammatory and immune responses resulting from infection and host defence mechanisms. In the last two decades, a number of cytokine therapy-based experimental and clinical trials have been conducted, and some of these efforts have led to the routine clinical use of cytokines. For instance, although IFNs have been used to treat hepatitis C with great success, many other cytokines are yet to be fully evaluated for their antimicrobial potential. This review discusses the biology and therapeutic potential of selected immune modulatory cytokines and their inhibitors, including granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, IFN-gamma, IL-12 and TNF.     

Role of interleukin-1 in bacterial atherogenesis

The high incidence of cardiovascular diseases resulting from atherosclerosis, especially in individuals lacking classic risk factors, has spawned interest in the possibility of unrecognized risk factors, such as chronic bacterial infection. Longstanding low-grade infections, such as periodontal disease, have the potential to affect distant sites in the body by inducing host cells to release inflammatory mediators into the bloodstream. Inflammatory mediators are released by macrophages upon interaction with activated T-helper cells or upon direct recognition of bacterial antigens, and by nonimmune cells upon recognition of antigen through Toll-like receptors. One key mediator, interleukin-1 (IL-1) is released in response to bacterial infection and is known to have specific proatherogenic properties. Increased levels of IL-1 enhance vascular adhesion, vascular permeability, macrophage activation, endothelial and smooth muscle cell proliferation, and protease-induced plaque rupture - all key steps in the progression of atherogenesis. In a recent study, we demonstrated a profound reduction in the progression of atherosclerosis in IL-1 knockout mice. IL-1 holds potential as a target for future antiatherosclerotic therapies, although given its ubiquity in the body, this would not come without unwanted side effects, such as immunosuppression.     

Functional biomaterials for comprehensive periodontitis therapy

Periodontitis is an inflammatory disease caused by bacterial infection directly, and the dysregulation of host immune-inflammatory response finally destroys periodontal tissues. Current treatment strategies for periodontitis mainly involve mechanical scaling/root planing(SRP), surgical procedures,and systemic or localized delivery of antimicrobial agents. However, SRP or surgical treatment alone has unsatisfactory long-term effects and is easy to relapse. In addition, the existing drugs for loca...     

Novel uses for anti-platelet agents as anti-inflammatory drugs

An alteration in the character and function of platelets is manifested in patients with inflammatory diseases, and these alterations have been dissociated from the well-characterized involvement of platelets in thrombosis and haemostasis. Recent evidence reveals platelet activation is sometimes critical in the development of inflammation. The mechanisms by which platelets participate in inflammation are diverse, and offer numerous opportunities for future drug intervention. There is now acceptance that platelets act as innate inflammatory cells in immune responses, with roles as sentinel cells undergoing surveillance, responding to microbial invasion, orchestrating leukocyte recruitment, and migrating through tissue, causing damage and influencing repair processes in chronic disease. Some of these processes are targeted by drugs that are being developed to target platelet participation in atherosclerosis. The actions of platelets therefore influence the pathogenesis of diverse inflammatory diseases in various body compartments, encompassing parasitic and bacterial infection, allergic inflammation (especially asthma and rhinitis), and non-atopic inflammatory conditions, for example, chronic obstructive pulmonary disease (COPD), rheumatoid arthritis (RA), inflammatory bowel disease (IBD) and atherosclerosis. This review will first discuss the evidence for platelet activation in these various inflammatory diseases, and secondly discuss the mechanisms by which this pathogenesis occurs and the various anti-platelet agents which have been developed to combat platelet activation in atherosclerosis and their potential future use for the treatment of other inflammatory diseases.     

Interleukin-12 and infectious diseases: a potential novel therapy

Interleukin-12 (IL-12) is emerging as a central component of both innate and acquired immunity. The multiplicity of biological activities associated with this cytokine, particularly the stimulation of cell-mediated immunity, suggests that it may be crucial in the control of extracellular and intracellular infections. In in vitro studies, IL-12 production is initiated rapidly after infection with a variety of viral, parasitic, fungal and bacterial agents. This induction correlates well with the reported resistance or susceptibility of animals to infection with these agents. Other factors may, however, influence responses in vivo, including host genetic make-up, microbial load and the induction of antagonistic cytokine pathways, notably IL-4 and IL-10. In some situations, IL-12 may direct immune responses to inappropriate pathways, and worsen disease, so that careful consideration of the type of required immune response is needed before IL-12 therapy is initiated. IL-12 treatment may also be useful in promoting protective immune responses to vaccines, allowing systemic immunisation with lower doses, or even normally non-immunogenic preparations, of antigen. Finally, IL-12 has been demonstrated to act in concert with standard antimicrobial chemotherapy in viral, parasitic, fungal and bacterial infections, allowing a reduction in the dose of the agent used and providing hope that such combination therapy may more effectively control drug-resistant strains of infectious agents.     

细菌种间相互作用及其对混合感染的影响

随着测序技术和独立培养鉴定方法的出现，人们发现许多细菌相关感染都表现为多种微生物混合感染，同时，人体原驻微生物群与感染病原体间的相互作用也会影响病程。相较于单一微生物感染，混合感染通常与感染严重程度的增加和患者预后较差有关。其机制可能是多物种微生物间通过化学物质或直接物理接触发生种间交流，从而产生协同作用以诱导毒力因子表达，竞争常驻微生物生态位以及调节宿主免疫应答等。本综述总结了细菌间相互作用的方式及其对混合感染的影响，旨在深入探索混合感染病理进程，为混合感染的干预治疗提供策略，拓宽抗菌药物发展思路。     

Role of coenzyme Q(10) as an antioxidant and bioenergizer in periodontal diseases

Periodontal disease is an inflammatory disease process resulting from the interaction of a bacterial attack and host inflammatory response. Arrays of molecules are considered to mediate the inflammatory response at one time or another, among these are free radicals and reactive oxygen species (ROS). Periodontal pathogens can induce ROS overproduction and thus may cause collagen and periodontal cell breakdown. When ROS are scavenged by antioxidants, there can be a reduction of collagen degradation. Ubiquinol (reduced form coenzyme Q(10)) serves as an endogenous antioxidant which increases the concentration of CoQ(10) in the diseased gingiva and effectively suppresses advanced periodontal inflammation.     

Fine-tuning of the mucosal barrier and metabolic systems using the diet-microbial metabolite axis

The human intestinal microbiota has profound effects on human physiology, including the development and maintenance of the host immune and metabolic systems. Under physiological conditions, the intestinal microbiota maintains a symbiotic relationship with the host. Abnormalities in the host-microbe relationship, however, have been implicated in multiple disorders such as inflammatory bowel diseases (IBDs), metabolic syndrome, and autoimmune diseases. There is a close correlation between dietary factors and the microbial composition in the gut. Long-term dietary habits influence the composition of the gut microbial community and consequently alter microbial metabolic activity. The diet-microbiota axis plays a vital role in the regulation of the host immune system, at least partly through altering microbial metabolism. In this review, we will describe the current findings regarding how dietary factors and microbial metabolites regulate the host immune system.     

Effects on the immune system

Marijuana and other exogenous cannabinoids alter immune function and decrease host resistance to microbial infections in experimental animal models and in vitro. Two modes of action by which delta9-tetrahydrocannabinol (THC) and other cannabinoids affect immune responses have been proposed. First, cannabinoids may signal through the cannabinoid receptors CB1 and CB2. Second, at sites of direct exposure to high concentrations of cannabinoids, such as the lung, membrane perturbation may be involved. In addition, endogenous cannabinoids or endocannabinoids have been identified and have been proposed as native modulators of immune functions through cannabinoid receptors. Exogenously introduced cannabinoids may disturb this homoeostatic immune balance. A mode by which cannabinoids may affect immune responses and host resistance maybe by perturbing the balance of T helper (Th)1 pro-inflammatory versus Th2 anti-inflammatory cytokines. While marijuana and various cannabinoids have been documented to alter immune functions in vitro and in experimental animals, no controlled longitudinal epidemiological studies have yet definitively correlated immunosuppressive effects with increased incidence of infections or immune disorders in humans. However, cannabinoids by virtue of their immunomodulatory properties have the potential to serve as therapeutic agents for ablation of untoward immune responses.