Sepsis-Induced Hypercytokinemia and Lymphocyte Apoptosis in Aging-Accelerated Klotho Knockout Mice

Abstract

Sepsis is primarily a disease of the aged, with 65% of sepsis cases reported in patients older than 65 years and 80% of deaths due to sepsis occurring in this age group. Klotho knockout mice (Klotho mice) are a mouse model of accelerated aging and shortened life span. The purpose of the study was to elucidate the immunological changes occurring in Klotho mice during sepsis. Five-week-old homozygous female Klotho knockout (Klotho) and wild-type (WT) mice were subjected to 1 × 27-gauge cecal ligation and puncture (CLP), and survival was compared after 4 days. Another set of mice was killed at 8 h after CLP or sham surgery, and the spleen, thymus, and serum were harvested. Apoptosis was measured by flow cytometry by using caspase 3. Serum cytokines and bacterial colony count in peritoneal lavage were also analyzed. Klotho septic mice started to die at 8 to 12 h after CLP, and the final survival of Klotho mice was significantly lower than that of WT mice (0% vs. 100%, P < 0.01). Increased bacterial count in the peritoneal cavity and decreased recruitment of neutrophils and macrophages to the peripheral cavity were observed in Klotho-CLP mice. Both flow cytometric and immunohistological analyses showed a dramatic increase in caspase 3-positive cells in the thymus and spleen of Klotho-CLP mice (P < 0.01). Serum concentrations of interleukin 6, tumor necrosis factor α, and interleukin 10 were higher in Klotho-CLP mice than in WT-CLP mice. Hypercytokinemia with impaired bacterial clearance and increased apoptosis of lymphocytes may be related to poor survival in Klotho-septic mice.

Severe Lymphopenia Is Associated with Elevated Plasma Interleukin-15 Levels and Increased Mortality During Severe Sepsis

“…Therefore, the severe lymphopenia in our patients could not be explained solely by decreased circulating leukocyte counts. A recent study reported increased lymphocyte apoptosis and decreased neutrophil and monocyte recruitment in aging-accelerated mice under experimental sepsis (29). The elderly study population might hint at decreased neutrophil or monocyte recruitment as the cause of the association between severe lymphopenia and decreased circulating neutrophils and monocytes.…”

Persistent inflammation and T cell exhaustion in severe sepsis in the elderly

“…However, some young mice also started to die at this time point (Figure 2B). Klotho knockout mice, in which both innate and adaptive immunity are severely impaired, have been found to die at a much earlier phase at 8 to 12 h after CLP [40]. Therefore, we can assume that the innate immune system was relatively functional in aged mice.…”

The intestinal microenvironment in sepsis

“…Notably, age appears to play a significant in gut apoptosis in sepsis. Murine models of sepsis have demonstrated significantly increased mortality in aged mice compared to younger animals (66–68), and aging is associated with increased gut epithelial apoptosis (69;70). …”