Chlamydia pneumoniae and Atherosclerosis: No Way-Out or Long Way?

Chlamydia Pneumoniae and Cardiovascular Disease in End-Stage Renal Disease Patients: An Update

Cardiovascular diseases (CVD), due to accelerated atherosclerosis, are responsible for approximately 50% of mortality in End Stage Renal Disease (ESRD) patients undergoing haemodialysis (HD). Over the last decade, Chlamydia pneumoniae, a respiratory pathogen, has been involved in the pathogenesis of atherosclerosis and several reports have suggested the association between C. pneumoniae infection and CVD in HD patients. This report reviews the contribution of C. pneumoniae infection in cardiovascular diseases in ESRD patients, in light of recent studies on cardiovascular risk factors; we hypothesize that C. pneumoniae-infection may contribute to mineral bone disorder and, consequently, vascular calcification. However, further studies are needed to define the relationship between C pneumoniae and bone and vascular disorders in HD patients.

[Acute renal failure following Chlamydia pneumoniae pneumonia in a child]

Acute renal failure (ARF) following Chlamydia pneumoniae pneumonia is rarely reported in adults. We present an observation in a 10-year-old child, who had C. pneumoniae pneumonia treated with roxithromycin for a period of 10 days, without any other nephrotoxic drug, in particular nonsteroidal anti-inflammatory drugs. At the end of antibiotic treatment, he presented with asthenia, polyuria, polydipsia, increased plasma creatinine, metabolic acidosis, hypokalemia, and markers of tubular damage. The etiological investigations showed positive C. pneumoniae antibodies, increased serum concentrations of C3 and C4 complement, IgA, and IgG. No uveitis was noted. The diagnosis was tubulointerstitial nephropathy after C. pneumoniae pneumonia. C. pneumoniae pneumonia should be considered a differential diagnosis of community-acquired pneumonia, especially in cases of poor response to conventional antibiotic therapy. It may be associated with tubulointerstitial nephropathy and/or rapidly progressive glomerulonephritis whose severity varies in children as in adults. Early and effective treatment of C. pneumoniae infection with macrolide antibiotics usually provides favorable progression of renal function.

Inflammation in atherosclerosis and other conditions: a response to danger

In the last few years atherosclerosis has been recognized as an inflammatory process. Assessment of low-grade inflammation with indexes like C-reactive protein (CRP) is considered indicative and potentially predictive for this disease. On the other hand, in a large number of clinical studies, a grade of microinflammation has been found to be associated with numerous other processes that may be directly, indirectly or not related to atherosclerosis. The most interesting finding these studies have yielded is that innate immunity is activated in various, previously unexpected, conditions. This phenomenon is better explained by the application of a recently proposed immune activation mechanism, namely, the 'danger model'. It seems that many conditions related to metabolic or homeostatic stress or to pro-atherosclerotic and pre-diabetic dysfunctions, established atherosclerosis or diabetes, but also other early tissue injury -- like renal, pulmonary or connective tissue -- and several exogenous stimuli, constitute 'danger signals' that induce inflammation which interacts with and complicates the above-mentioned processes. On this basis the complex relationships between CVD risk factors, atherosclerotic process, other tissue injury and inflammation is examined. The practical application of this hypothesis, namely the new clinical use of CRP as a sensitive -- although not specific for atherosclerosis -- index of low-grade inflammatory activity as well as to the atherosclerosis treatment are also discussed.

Serum and peripheral blood mononuclear cells infectious burden: Correlation to inflammation and atherosclerosis in haemodialysis patients

BACKGROUND

Infectious agents may be implicated in the inflammatory atherosclerotic process. Not only specific microorganisms but also the infectious burden, defined as the number of pathogens to which a patient is exposed, has been associated with atherosclerosis. In the present study, the infectious burden, determined directly (by identification of viable pathogens in peripheral blood mononuclear cells (PBMC)) and indirectly (by serum antibodies detection) is correlated to the inflammatory and atherosclerotic status in haemodialysis (HD) patients, a population at high risk for cardiovascular disease.

METHODS

The viable forms of four microorganisms (Chlamydia pneumoniae, herpes virus 1 and 2 and cytomegalovirus) were identified in patients PBMC by cell cultures and subsequent polymerase chain reaction. Serum IgG against the above pathogens and Helicobacter pylori were also determined. Inflammation was assessed by measurement of C-reactive protein (CRP), serum amyloid A (SAA), three pro- and one anti-inflammatory cytokines and four adhesion molecules. Atherosclerosis was defined by a scoring system using medical history data.

RESULTS

The number of viable pathogens identified in PBMC in the 122 HD patients included in the study were zero in 22.1% of them, one in 33.6%, two in 43.4% and three in one patient. The number of IgG antibodies determined was one in 6.6% of patients, two in 32%, three in 48.4% and four in 13.1%. Seropositivity was not significantly different between patients with or without the respective viable pathogen identified in PBMC. Atherosclerosis was present in 40.2% of patients, and CRP, SAA and interleukin-6 were all increased in these patients. Neither inflammatory indexes nor atherosclerosis were significantly different in patients with a higher number of viable pathogens detected in PBMC or in those with a higher antibodies number.

CONCLUSIONS

The direct infectious burden determination (the number of viable pathogens in PBMC) does not coincide with the serum (by IgG detection) infectious burden. Although inflammation correlates to atherosclerosis, neither PBMC nor the serum infectious burden is associated with these two entities in the inflamed and atherosclerotic HD patients.

Heat Shock Proteins in Vascular Disease—A Review

INTRODUCTION

There is growing evidence that heat shock proteins (HSPs), a family of stress-inducible proteins may be involved in the pathogenesis of atherosclerotic vascular diseases. Here, we systematically review the evidence behind this notion.

METHODS

A detailed literature search and extensive bibliographic review of literature relating to HSPs and atherosclerotic vascular disease.

RESULTS

Atherosclerotic vascular disease is classified into four main areas of presentation: carotid, coronary, aortic and peripheral vascular disease, for consideration in this review. In each of these vascular diseases, the evidence linking HSPs and atherosclerosis is outlined in a systematic manner. Current evidence suggests that components of the immune system may be involved in the pathogenesis of atherosclerosis, with HSPs acting as auto-antigens in the immune response. HSPs are detected in atherosclerotic lesions and antibodies to HSPs are increased in patients with vascular disease; the rise often correlating with the severity of atherosclerosis. The levels of anti-HSP antibodies have been shown to be independent predictors of risk and have prognostic value.

CONCLUSION

There is a strong link between heat shock protein expression and the principal manifestations of atherosclerotic vascular diseases. A better understanding of this involvement could lead to the development of new and improved treatment strategies.